ANNUAL REPORT 1995
••••
Research Station for Fruit Growing Brugstraat 51 4475 AN Wilhelminadorp The Netherlands
Phone+31-113-242500 Fax+31-113-242650 Postgironr 495017
Information contained in this report may not be reproduced in total or in part without permission. Neither the authors nor the Research Station can accept any liability of loss, damage or injury resulting from the application of any concept or procedure in or derived from any part of this report.
ISSN 1381-6594 Price Dfl 25.00 A.R. 1995 Research Station for Fruit Growing
The research on fruit growing is funded by the Ministry of Agriculture, Nature Conser vancy and Fishery, Landbouwschap and Produktschap voor Siergewassen (PVS).
landbouw, natuurbeheer en visserij
Postbus 20401, 2500 EK Den Haag Tel. 070 3793911
Landbouwschap
Prinsenvinkenpark 19, 2585 Den Haag Tel. 070 3526666
OOP OGV
Postbus 93099, 2509 AB Den Haag Tel. 070 3041234 CONTENTS PAGE
Remarks on the brands of pesticides and herbicides 1 Donor Members 1 Board 2 Staff 3 The Experimental Garden
Weather and full bloom data 6 Department of Pomology and Economics
Top Fruit and Nursery Rootstocks and interstems for pome and stone fruit 8 (apple rootstock trial - cherry rootstock trial) Unusual fruit crops 14 (Hazelnut - walnut - quince) Fruit-tree nursery 19 (effect of benzyladenine on feathering of trees in the nursery)
Planting systems and light utilisation 21 (planting systems with Jonagold, Fiesta and Elstar)
Evaluation growth regulators 25 (Pre-harvest drop control Conference pear - evaluation of GA4-rich mixture for russeting control - evaluation of auxin-protein conjugates for rooting of cuttings - growth control with a retardant)
Pruning and tree shapes 28 (Growth control Conference)
Fruit quality, orchard and climate 30 (Influence of light on fruit quality for four rootstocks - pruning and thinning with Elstar - simulation of fruit growth during the season)
Black skin discoloration in pear 34
Chemical thinning 36 (Evaluation of new thinning compounds on apple - early thinning of Elstar a necessity - olanting trees on or in the ground)
Evaluation of Top Fruit Cultivars pultivar testing with apple 44 (cultivar testing in Wilhelminadorp - clone trials in Wilhelminadorp - clone trials in regional experimental gardens)
Cultivar testing with pear 49 (cultivar testing in Wilhelminadorp)
Cultivar testing with stone fruit 51 (cultivar testing with plum in Wilhelminadorp - cultivar testing with sweet cherry in Ahrweiler (Germany) - cultivar testing with sweet cherry in Rillaar (Belgium))
The pollination of pome and stone fruit 53 (crossings)
Small Fruit Strawberry cultivar trials 54 (cultivars in the open - everbearing cultivars - other strawberry trials)
Cultivar trials of bush and cane fruits 56 (red and white currant - black currant - gooseberry - blackberry - raspberry - blueberry)
Development of methods for an early and late harvest of currants, raspberries, blackber ries and blueberries 70 (early and late harvest with blueberries in a mobile tunnel - late harvest of blueberry by means of rain covers - late harvest and the effect of soil treatment with Elliott)
Economics and Farm Management Analysis Intergrated fruit growing ' 73
Decision support systems in fruit growing 75 (a decision support system for economic and ecological calculations - price and quality)
Plant Nutrition and Fruit Quality
Physiology Fruit ripening as affected by environmental factors during the growing season .... 79 (the effect of temperature at early and late stages in the season on some of the riping and quality criteria in apple)
Storage and Quality Prediction of optimum harvest date for long-term storage in apple and pear 82 (first picking date for direct consumption) Optimum harvest date of apples for direct consumptium and for prolonged storage . 84 (aim - materials and methods - results) Distribution of fruit quality in the tree at harvest and post-harvest behaviour in relation to the effect of fruit position in Elstar 89 (aim - methods - results - nutrient relations - correlations between fruit characteristics - simulated picking) Optimum storage conditions and the suitability of storage techniques for fruit 95 (aim - new cultivars - Jonagold mutants - results)
Prediction of risk on superficial scald in Jonagold 99 Fungicide reduction in spray scheme for controlling storage rot 102
Pre- and postharvest fruit quality in relation to nutrition and other orchard factors . 104
Reduction of internal disorders during storage of Conference pear 106 (aim - method - results)
Skin spots on Elstar 108 (aim - the effect of calcium spraying - results - effect of pull-down and speed warming- up)
Soil Science and Plant Nutrition Control of growth and production of pit and stone fruit by water and nutrient supply110 (advisory system for the water supply - water project Zeeland)
Improvement of the quality of pit and stone fruits through the water and nutrient supply 102 (calcium fertigation)
Water and nutrient requirements of strawberries and berry fruit 116 (water requirement of blueberry)
Optimization fertilization - recommendation basis for strawberry and bush and cane fruit 117 (optimization fertilization blueberry)
Crop Protection
Phytopathology and Weed Control Biology and control of secondary or sporadic disease in fruit crops 118 (European canker - root rot in pear - fruit rot on blueberry)
Biology and control of apple scab 119 (development in spring - testing fungicides - resistance to DMI fungicides - leaf drop accelaration)
Biological control of diseases in fruit crops 120 (powdery mildew on gooseberry)
Population dynamics of Pratylenchus penetrans in fruit crops 121 (comparison of various preceding crops for the control of replant disease caused by the nematode Pratylenchus penetrans - optimization of alternatives for chemical soil disinfection - control of nematodes with bacteria - alternatives for chemical soil disinfection - origin of planting material and soil treatment - testing of various root- stocks for their susceptibility to nematodes - ridge culture with potting soil against nematodes - strip disinfection compared to overall disinfection)
Entomology and Biological Control Testing of insecticides, fungicides and bactericides in fruit growing 129 (tests of three potential aphicides - tests of insecticides against the mullein bug) Integrated control of pests on top fruit 130 (Integrated control of pests on apple - carnation leaf-roller - damage by bugs)
Biological control of pests on strawberry and soft fruits 132
Development of farming systems for integrated fruit growing 132 (aim - materials and methods - results in 1995 - farming systems research for scabresis- tant apple cultivars - results - conclusion)
List of Chemicals 145
Publications 147
List of Entries 152
Publications of the Research Station for fruit growing 161 Remarks on the brands of pesticides and herbicides
The dosages mentioned for pesticides and herbicides in this report refer to the commer cial products. Trade names of products have been used for the sake of convenience, but this makes it unavoidable that in some cases similar endorsement of named products is intended. Some of the experiments described in this report are carried out with chemicals and/or concentrations not yet legally improved.
Donor members
Those who are interested in the work of Research Staion and wish to keep an active touch with and support its research, are invited to become donor member. Donor members will receive the Annual Report and other publications of the Research Station without charge. The minimum subscription for donor membership is 35 guilders for private individulas in The Netherlands, 60 guilders for institutions in The Nether- ands, and 50 guilders for foreign private individuals and foreign institutions, annually. 3aymant by transfer to an account of the Proefstation voor de Fruitteelt (post office giro account nr. 49 50 17, account ABN/AMRO-bank Goes nr. 47.21.74.878) or by nternational postal money order in Dutch currency, payable to the Proefstation voor de zruitteelt at Wilhelminadorp, with the indication "Donorship Subscription". Jaarverslag FPO 1995
Board (31 December 1995)
Board of the foundation research station for fruit growing
Executive committee Other members
J.A.M. Musters, Dinteloord, chairman F.J. van Beerendonk, Best
H.W.M. Kurver, vice-chairman C.J.M. Geraeds, Den Haag
A.H. Tap Dodewaard, secretary Ir. J.L. Grève, Den Haag
G.A. van Haarlem, Buurmalsen Advisors Ing. C.G.M, van Leeuwen, Den Haag Ir. J.M. Gerritsen H.E.P. Reinders, Helden-Panningen J. Zevenbergen H.F.M. Schrama, Biddinghuizen Ir. R.J.M. Meijer G. de Weert, Rossum
J. van Woudenberg, Niehove
vacancy
vacancy Jaarverslag FPO 1995
Staff (31 December 1995)
Research Station for Fruit Growing
Directeur: Ir. R.J.M. Meijer
omology and Economics Dr.Ir. S.J. Wertheim (head, deputy director)
Top Fruit and Nursery Dr. Ir. S.J. Wertheim vlrs. Ing. J.M.T. Balkhoven-Baart vlrs. Dr. P.S. Wagenmakers J.M. de Groene vi. Tazelaar Evaluation Top fruit Cultivars ng. H. Kemp Small Fruit äi.J.P. van de Waart Economics and farm Management Analysis J. Goedegebure vlrs. Ir. M.J. Groot ibrary and Editorial staff vlrs. M.M. Cremers-van Scherpenzeel
'lant Nutrition and Fruit Quality Dr.lr. A. de Jager (head)
»oil Science and Plant Nutrition r. M.P. van der Maas "hysiology rof. Dr. J. Tromp :h.A.R. Römer Storage and Quality Dr.lr. A. de Jager ng. F.P.M.M. Roelofs ng. H. de Putter aboratory ulrs. Ing. L.M. van Westing (head) k/lrs. M.T.T. de Leeuw-Vereecken »/Irs. A.M. Meerman-van de Repe yirs. P.C. Rijk Jaarverslag FPO 1995
Mrs. D.T. Slazak Mathematics and Statistics E.M.A. van Remortel
Crop Protection Dr.ir. B. Heijne (head)
Spraying Techniques Dr.ir. B. Heijne R.H.N. Anbergen Entomology and Biological Control Ir. J. Woets Integrated Fruit Control Mrs. Ir. A.M.E. Schenk H. Veijer Data Management W. Beeke
Coordination and Public Relation Ir. J.A. Jobsen
Administration and Support Services J.A.M. Kouwenberg (head)
Administration Mrs. A.M.Th. Mateijsen Mrs. T.L. Buizer-Schuit Mrs. M.C. Schrier-Nijssen Mrs. J.G. Snaterse-van Loo Mrs. P.E. van Vossen-Hopmans Mrs. M.S. Westerweele-Korsuize Housekeepers Mrs. D.N. Nijsse-Hoogesteger Mrs. M.M. Stuck Experimental Garden and Engineering J.L. Baarends (head) J. de Schipper D.R.M. Acda M.C. van Maris P.C. Oostdijk S. Smits J. van Dalen
Stichting Cluster ZO-Nederland J.J.C. Driessen Jaarverslag FPO 1995
[Regional Experimental Orchards
Stichting Proeftuin Noord-Brabant, Breda r. J.A. Jobsen (director) ng. Sj. Rinsma vl.H. van de Rijt \.C. Oomen \.M. Konings H.M.J.H.G. van Westen-Schuurbiers
Stichting Fruitteeltproeftuin Midden-Nederland, Geldermalsen r. J.A. Jobsen (director) ".A. van Zuidam N.C. van Eldik ^.C.M. Sturkenboom
Stichting Fruitteeltproeftuin voor Limburg en Noord-Brabant, Horst r. J.A. Jobsen (director) rh.S.G.M. Veens */lrs. Ing. W.A.G.M. Jansen Z. Wullems
:ruitteeltproefbedrijf van de Vereniging "Naar Beter Fruit", Numansdorp (tuin gesloten >p 31-3-1995) r. J.A. Jobsen (director) H. Veijer
Stichting Fruitteeltproeftuin voor Noord-Nederland, Zeewolde r. J.A. Jobsen (director) V. Lugtenberg ng. J.H. Bootsma i/lrs. J.J.H. Dekker-Kets :.J. Nagelhout I.A. Schoutsen
Division Fruit Production of the national Reference Centre for Arable :arming and Horticulture r. P.A.M. Besseling r. E.J.M. Regouin Msc. /I.L. Joosse A.R. 1995 Research Station for Fruit Growinc
The experimental garden
Weather and full bloom data
P.S. Wagenmakers
Table 1 lists data on global radiation, precipitation and temperature for Wilhelminadorp Long-year averages were presented for Vlissingen because these data were missing fo Wilhelminadorp. Because Vlissingen is closer to the North Sea, slight differences occu between the two stations. The significance of these on fruit performance is, however small. The winter of '94-'95 was extremely warm, with temperatures for November tc April being 3°C above the average. April and May were 1 °C warmer than normal. Ma' was sunny as well. June was rather normal, but July and August were sunny and ver> hot, with mean temperatures of 20°C. The summer was dry. The nice weather ended ii September. That month, there was twice as much rainfall as normal, and it was cloudy Temperatures were even 5°C lower than those in August. October was quite nice an« dry. A cold winter period started in December, with an average temperature of less thai 1°C.
Table 1. Mean daily temperature (1994 and long-year average) for Wilhelm! nadorp (Wi) and Vlissingen (VI)
Month Global radiation Precipitation Temperature (MJ/m2/month) (mm) (°C)
Wi VI Wi VI Wi VI 1995 1951- 1995 1951- 1995 1951- 1990 1990 1990
January 80.1 78.8 136.0 65.9 4.7 3.1 February 126.2 143.6 90.3 46.3 7.2 3.1 March 332.3 274.4 59.8 55.9 6.1 5.2 April 382.1 412.0 34.4 45.6 9.1 8.0 May 612.0 563.9 39.4 46.5 13.0 11.9 June 545.0 587.1 68.4 63.6 14.5 14.9 July 646.6 563.4 51.4 68.7 20.0 16.7 August 587.1 489.1 36.3 80.1 20.2 17.0 September 286.9 342.7 161.6 70.9 14.5 15.2 October 203.6 209.6 16.3 81.4 12.8 11.7 November 98.8 97.5 58.6 76.9 7.8 7.2 December 60.7 61.7 45.4 72.9 0.6 4.5 average 330.1 318.7 66.5 64.6 10.9 9.9 A.R. 1995 Research Station for Fruit Growing
:ull bloom of the plums was in 1995 9-12 days earlier than normal (Table 2). The pears and apples were 6 days earlier than normal. rable 2. Data of full bloom at Wilhelminadorp between 1991 and 1995 (plum, pear, apple)
'ultivar 1991 1992 1993 1994 1995 1973 t/m 1992
)pal 8-4 11-4 9-4 15-4 10-4 19-4 /ictoria 8-4 12-4 4-4 13-4 6-4 18-4
Conference 12-4 20-4 16-4 20-4 19-4 25-4 )oy.d.Cornice 14-4 26-4 20-4 27-4 25-4 30-4
Mkmene 17-4 1-5 25-4 4-5 30-4 5-5 ilstar 29-4 4-5 28-4 9-5 3-5 11-5 Jonagold 29-4 2-5 25-4 4-5 3-5 10-5 Solden D. 25-4 3-5 27-4 9-5 3-5 10-5 A.R. 1995 Research Station for Fruit Growing
Pomology and Economics
Top fruit and Nursery
Rootstocks and interstems for pome and stone fruit
S.J. Wertheim and J.M.T. Balkhoven-Baart
Apple rootstock trial 044 8901
At the end of 1995, the national apple rootstock trial planted in the spring of 1989 ir the experimental gardens at Horst (Ho), Wilhelminadorp (Wi) and Zeewolde (Ze) was terminated. Ze represented a vigorous sea clay soil and Wi a moderate one and Ho e sandy soil. The aim of the trial was to find a rootstock with a vigour between that o1 M.27 and M.9. The former is often too dwarfing and moreover not winterhardy in the nursery, the latter can be too vigorous on good soils. For the nursery industry e rootstock between M.9 and M.26 is also of interest for export reasons. The scior cultivars in the trial were Cox's Orange Pippin and Jonagold. The rootstocks involvec (Table 1) were virus free but not the same in all gardens. The planting distances variée somewhat per site and were different for various replicates within one garden: in Ze 3 > 1.10, 1.30 or 1.50 m, in Wi 3.25 x 1.05, 1.20 or 1.30 m, in Ho all distances were 3.40 x 1.40 m. Tables 1 to 3 give some general results, but a common statistica analysis still has to be made.
Trunk circumference
Table 3 gives the final trunk circumference measured in the winter of 1995/96. The sequence in vigour was not the same for all sites. Table 3 gives a sequence based or the trunk sizes of Cox in Wi. With Cox Orange Pippin B.491 and P.22 were equally dwarfing than M.27 in Wi anc Ze, but in Ho P.22 was more vigorous. B.146 was also dwarfing, but was stronger thar M.27 in Ho en Ze. In all gardens, P.16 had a vigour between those of M.27 and M.9 and is therefore of interest. B.469, too, was in between the two standards in Wi anc Ze, but in Ho it was equal to M.9. The German J.9 was rather variable; less vigorous than M.9 in Ze, equal to M.9 in Wi and more vigorous in Ho. So, here the soil plays z role. 0.3 grew stronger than M.9 in Ho, but not in Wi. M.26 only occurring in He indeed proved to be a vigorous rootstock compared to M.9. KSC 28 was only presen' in Wi and here the trunk size was not in proportion to the tree size, which was ver\ large. With Jonagold the sequence in vigour was roughly similar to that of Cox. It is worthy of note that again P.1 6 was in between M.27 and M.9. Here, too, the KSC 2£ trunk was not a good measure for the tree size. A.R. 1995 Research Station for Fruit Growing
Table 3. Growth vigour apple rootstock trial 044 8901
Root- Cox's Orange Pippin Jonagold stock Wi Ze Ho Wi Ze Ho
Trunk circumference (cm) winter 1995/'96 B.491 14.3 a 15.3 a 16.8 a 15.0 a 14.6 a 15.8 ab M.27 14.7 ab 15.4 a 15.0 a 14.5 a 14.9 a 14.3 a P.22 15.0 ab 16.3 a 17.5 b 14.2 a 14.3 a 15.6 ab
B.146 16.6 be 18.7 b 20.1 cd 16.9 b 16.4 bc 15.4 ab KSC 28 17.6 c - - 17.1 bc - - P.16 18.3 cd 19.1 bc 18.6 bc 17.8 bc 16.4 bc 17.1 b B.469 18.4 cd 18.3 b 20.5 cd 18.6 cd - -
J.9 20.0 de 20.2 c 24.0 ef 17.3 bc 17.1 c 19.4 c M.9 20.5 e 21.6 d 20.9 d 19.5 d 18.8 d 20.7 cd 0.3 20.9 e - 23.8 e 19.7 d - 22.0 d M.26 - - 26.1 f - - 26.7 e
F-test <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 LSD 5% 1.97 1.23 2.25 1.67 1.01 2.18 Tree-head volume (rrv J) winter 1995/'96 B.491 0.91 ab 0.95 ab 0.99 b 0.65 ab 0.82 ab 1.104 bc M.27 0.71 a 0.90 a 0.64 a 0.56 a 0.82 ab 0.58 a P.22 0.82 a 0.86 a 1.01 b 0.49 a 0.78 a 0.85 ab
B.146 0.97 ab 1.17 bc 1.27 b 0.74 bc 0.92 abc 0.73 a KSC 28 3.00 e - - 2.31 e - - P.16 1.44 cd 1.06 ab 1.26 b 0.92 cd 1.03 cd 1.26 cd B.469 1.25 bc 1.18 bc 1.10 b 0.90 c —
J.9 1.41 cd 1.07 ab 1.59 cd 0.88 c 0.95 bed 1.48 de M.9 1.52 cd 1.34 c 1.28 bc 0.96 d 1.14d 1.65 ef 0.3 1.68 d - 1.86 de 1.11 d - 1.88 f M.26 - - 2.04 e - - 2.49 g
F-test <0.001 0.006 <0.001 <0.001 0.011 <0.001 LSD 5% 0.39 0.24 0.31 0.20 0.20 0.29
Values in one colomn followed by th e same letter s) do not differ significantly
9 A.R. 1995 Research Station for Fruit Growing
Table 4. Total production 1990-'95 apple rootstock trial 044 8901
Root Cox's Orange Pippin Jonagold stock Wi Ze Ho Wi Ze Ho
Kg/tree B.491 56.5 bc 55.7 a 66.1 ab 112.7 b 119.8 b 106.1 b M.27 46.3 a 52.9 a 53.6 a 93.6 a 107.1 ab 78.4 a P.22 50.8 ab 56.1 a 64.4 ab 90.7 a 95.7 a 96.7 ab
B.146 61.7 cd 71.6 b 76.6 cd 124.1 bc 124.2 b 96.8 ab KSC 28 83.0 f - - 114.0 b - - P.16 76.6 ef 87.0 cd 91.2 d 149.6 e 151.3 c 144.3 c B.469 67.0 d 80.2 bc 75.2 b 145.3 de - -
J.9 81.1 f 90.7 cd 114.3 e 131.3 cd 173.0d 168.0d M.9 79.3 f 95.5 d 96.9 d 146.7 de 177.3 d 167.9 d 0.3 70.2 de - 89.2 cd 124.7 bc - 165.6 M.26 - - 101.1 de - - 176.2 d
F-test <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 LSD 5% 8.65 13.89 13.65 16.37 19.78 22.54 Fruits/m3 tree volume B.491 434 ab 402 a 500 b 833 ab 724 a 489 c M.27 462 a 399 a 650 a 864 a 731 a 791 a P.22 407 ab 450 ab 458 b 828 ab 712 a 641 b
B.146 433 ab 413 ab 462 b 905 a 708a 649 ab KSC 28 194d - - 234 e - - P.16 358 abc 506 bc 516 b 682 bc 717 a 550 bc B.469 371 abc 436 ab 513 b 776 abc - -
J.9 358 bc 567 c 490 b 622 cd 860 a 540 bc M.9 349 bc 434 ab 525 b 647 c 730 a 463 c 0.3 289 cd - 302 c 483 d - 417 cd M.26 - - 309 c - - 317 d
F-test <0.001 0.008 <0.001 <0.001 0.275 < 0.001 LSD 5% 105.3 83.1 97.3 162.7 ne 143.7
Values in one colomn followedby the same letter(s) do not differ significantly (P= 0.05). nc= not calculated; P-value >0.05.
Tree volume
The tree volumes in Table 3 roughly show the same trend as the trunk circumferences Of course, tree size was affected by pruning, so the trunks give a better estimate of
10 A.R. 1995 Research Station for Fruit Growing
Table 5. Production/ha and fruit weight 1990-'95 apple rootstock trial 044 8901
Root Cox's Orange Pippin Jonagold stock Wi Ze Ho Wi Ze Ho
Tonnes/ha*) B.491 188 186 220 376 399 354 M.27 154 176 179 312 357 261 P.22 169 187 215 302 319 322
B.146 206 239 255 414 414 323 KSC 28 158 - - 217 - - P.16 232 264 276 453 458 437 B.469 203 243 228 440 - -
J.9 216 242 305 350 461 448 M.9 211 255 258 391 473 448 0.3 187 - 238 333 - 442 M.26 - - 192 - - 335 Mean fruit weight (g) B.491 152 ab 158 a 148 b 225 ab 213 ab 206 b M.27 154 ab 156 a 135 a 218 a 205 a 197 ab P.22 167 d 157 a 144 ab 233 bc 211 ab 189 a -
B.146 151 a 161 a 148 b 226 ab 215 abc 200 ab KSC 28 153 ab - - 222 ab - - P.16 164 cd 168 b 148 b 243 cd 221 bed 207 bc B.469 162 bed 160 a 146 b 234 bc - -
J.9 171 d 168 b 152 bc 260 e 231 d 219 d M.9 166 cd 169 b 150 b 251 de 227 cd 218 cd 0.3 157 abc - 162 cd 242 cd - 222 de M.26 - - 167 d - - 232 e
F-test <0.001 <0.001 <0.001 <0.001 0.006 <0.001 LSD 5% 9.5 5.8 10.7 13.8 13.2 11.2
Values in one colomn followed by the same letter(s) do not differ significantly (P= 0.05). *) for planting distances, see text. vigour. As was stated before, the size of trees on KSC 28 was not in proportion to with their trunk dimensions. In Ho trees on M.27 lagged behind compared with the two clay sites. Possibly, M.27 is not so well adapted to a sandy soil. The data on tree size were used for calculations for tonnes per ha (Table 5). Production Table 4 summarizes the accumulated tree production for the whole experimental period.
11 A.R. 1995 Research Station for Fruit Growing
Of course, large trees can yield more kg than small ones with a similar degree of fruit set. Therefore, Table 3 also gives the accumulated fruit numbers per m3 of final tree- head volume. It can be seen in Table 3 that in tree yield M.27 was rather poor compa red to the similarly vigorous B.491 and in some cases also to P.22. Further it appears that P.1 6 trees were more productive than comparable trees on B.469. KSC 28 produced low yields given its large tree heads. It appears that the more dwarfing the rootstock the higher the numbers of fruit per unit of tree volume. In Ho, M.27 had a very high number of fruits which possibly is the reason for the weak growth there. P.1 6 was equal to M.9 in productivity per m3 tree volume, which is of interest given its vigour. The more vigorous rootstocks 0.3 and M.26 gave rather low fruit numbers per m3 and for KSC 28 this was especially so. Production per ha depends of course on planting density. For a good estimate it was decided to take 3.00 x 1.00 m for the four most dwarfing rootstocks as a basis for calculation of tonnes per ha from kg per tree. For P.1 6 and B.469 3.00 x 1.10 m was taken, for J.9, M.9, and 0.3 3.00 x 1.25 m, and for M.26 and KSC 28 3.50 x 1.50 m. Table 3 summarizes the ha productions accumulated for all years. It appears that B.491, M.27, and P.22 were rather low in production, especially M.27. Of course, with higher tree numbers per ha, possible with such rootstocks, production levels may be higher. The dwarfing B.146 produced well as did the other rootstocks except the vigorous M.26 and KSC 28. In Ho Cox on J.9 did very well. Here, Cox on J.9 was noticeable for its healthy leaves.
Fruit size
Table 5 also gives the fruit weights averaged for the whole experimental period. This only gives a rough idea, because differences between years can be masked and differences in fruit bearing per unit of tree volume were not considered. If possible, correction will be made for this in later analyses. With all these shortcomings, fruit size was smallest on the four most dwarfing rootstocks and surprisingly on the vigorous KSC 28. So, the very dwarfing stocks need a lot of attention with regard to fruit thinning. Cox on P.22 in Wi was a favourable exception. Fruit size on all other root- stocks was good.
In summary, in the most dwarfing range P.22 and especially B.491 were shown to be better than M.27. For situations where so far M.27 has been recommended this is of special interest, and also for areas with severe winters. B.146 although its vigour, productivity, and fruit size were good is of less interest, because there were too many juvenile characters, such as root suckers and burr knots on the rootstock shanks. If a less juvenile B.146 could be found, this rootstock would warrant further testing. In the interesting range between M.27 and M.9 two rootstocks came forward, B.469 but especially P.16 . With the latter more experience has to be gained. A large trial is being prepared. J.9 and 0.3 are of less interest for The Netherlands, because these do not offer more than M.9, but 0.3 may be of interest in areas with harsh winters. Of no interest are M.26 and KSC 28 because of their strong vigour and low productivity.
12 A.R. 1995 Research Station for Fruit Growing
Table 6. Results cherry rootstocks trial 044 8821
Root- Trunk Increase Kg/tree Kg/cm Fruit stock circumf. trunk circ. trunk weight (cm) (cm) circumf. (g) autumn spring '88 - 1995 autumn '95 1991 till 1995
Early Rivers Inmil 20.0 a 15.7 a 5.55 a 0.27 a 5.4 a Damil 27.6 b 22.3 b 14.25 ab 0.46 a 6.1 c Camil 35.7 c 30.0 c 29.70 c 0.85 b 6.0 c Weiroot 10 45.0 d 38.9 d 54.89 d 1.21 c 5.8 b Weiroot 13 48.9 d 42.5 d 56.92 d 1.15 c 5.7 b Colt 45.1 d 37.9 d 19.65 be 0.42 a 5.9 be F-test <0.001 <0.001 <0.001 <0.001 <0.001 LSD 5% 5.40 5.28 13.996 0.263 0.26 Castor Inmil 22.8 a 18.5 a 12.66 a 0.55 a 7.5 a Damil 32.3 b 26.3 b 24.76 b 0.76 b 8.1 be Camil 35.8 b 30.6 b 35.90 c 0.97 c 8.3 c Weiroot 10 49.5 c 43.2 c 61.81 d 1.25 d 7.7 ab Weiroot 1 3 50.6 c 43.7 c 69.58 d 1.37 d 7.7 ab Colt 53.0 c 45.1 c 23.97 b 0.45 a 8.6 c F-test <0.001 <0.001 <0.001 <0.001 0.002 LSD 5% 4.90 4.85 10.204 0.201 0.51 Merton Glory Inmil 25.6 a 20.6 a 21.73 a 0.83 ab 6.9 a Damil 30.2 b 24.4 a 21.79 a 0.69 a 9.2 b Camil 40.0 c 34.6 b 45.75 b 1.13 b 9.0 b Weiroot 10 54.1 d 47.6 c 113.58 c 2.09 c 8.2 b Weiroot 1 3 56.8 d 49.7 cd 119.24c 2.10c 8.2 b Colt 59.5 e 52.1 d 37.59 b 0.63 a 9.1 b F-test <0.001 <0.001 <0.001 <0.001 0.001 LSD 5% 3.91 3.79 13.662 0.312 1.03 Stella Inmil 22.4 a 17.7 a 21.28 a 0.94 a 7.6 a Damil 30.4 b 25.0 b 50.95 b 1.69 b 8.4 b Camil 33.7 b 27.8 b 70.24 c 2.09 c 7.9 a Weiroot 10 45.0 c 34.0 c 105.28 d 2.34 cd 7.9 a Weiroot 1 3 47.6 c 40.4 c 126.32 e 2.66 d 7.9 a Colt 54.6 d 47.3 d 74.29 c 1.36 b 8.6 b F-test <0.001 <0.001 <0.001 <0.001 <0.001 LSD 5% 2.90 2.87 14.127 0.374 0.41
Values per cultivar in 1 column followed by the same letter(s) do not differ significantly (P = 0.05); calculated with the LSD-value mentioned.
13 A.R. 1995 Research Station for Fruit Growing
Cherry rootstock trial 044.8821
The international rootstock trial with sweet cherry planted spring 1988 was ended autumn 1995. The results will be presented at the ISHS cherry symposium to be held in 1997 in Norway/Denmark. Earlier results of the Wilhelminadorp replicate were published in the Annual Reports 1989 (p. 32-33), 1990 (p. 18), 1991 (p. 39-40), and 1992 (p. 37-38). Table 6 summarizes some general outcomes. The results have only been analysed per cultivar, a common analysis for all four cultivars will follow later. The same holds for an analysis for all participating countries. The trunk data in Table 6 show that Inmil was the most dwarfing rootstock. Thereafter came Damil; with two cultivars the vigour was equal to that of Camil, with two other cultivars Camil was more vigorous. Both were less vigorous than the Weiroot-numbers that were about equal in growth vigour. Colt was the strongest rootstock in the trial, although in most cases not significantly different from the Weiroot-numbers. Producti ons per tree were rather different, partly because of the differences in tree size, partly because of the rootstock effect. The latter is to be seen in the data on kg per cm trunk circumference. In this respect, Inmil, Colt and Damil scored rather low compared to the two Weiroot-numbers; Camil had an intermediate position. Fruit size data were not corrected for differences in cropping per unit of growth. The non-corrected data in Table 6 show that Inmil generally gave small sized fruit as opposed to Damil. In summary, the trial did not render a good real dwarfing rootstock. Inmil was a dwarfing stock but had some drawbacks (poor ramification, low productivity per unit of growth, small cherries). It may be suitable for large-fruited cherry cultivars, but only if branching is improved by regular pruning or by other means. Damil and Camil were not really dwarfing and had rather unhealthy looking leaves. Fruit size on these two rootstocks was good. The Weiroot-number were by no means dwarfing, but gave healthy productive trees. Their sole disadvantage is the high rate of root suckering. These rootstocks appear suitable for a successful extensive culture. Colt proved a rather vigorous but not very productive rootstock. In that vigour range both Weiroot- numbers were much better.
Unusual fruit crops
S.J. Wertheim and H. Kemp
Hazelnut {Cory/us sp.)
S.J. Wertheim
The main criterion in the evaluation of hazelnut cultivars is productivity. For an economic culture the ha-yield should exceed 2 tonnes per ha. Tree number per ha will' vary between 667 (5 x 3 m) to 1,000 (4 x 2.5 m). This means that the average tree production in the productive phase must exceed 2 kg. Of course, other features are also of importance, such as kernel blanching during roasting. Only if the pellicles of the kernels are easily removed will an attractive product be produced. The figures given
14 A.R. 1995 Research Station for Fruit Growing hereafter are mostly based upon 3 replicates of 2 trees each.
Hazelnut trial 1982
Table 7 shows the production throughout the years of all cultivars present in the original trial. The cultivars marked with an asterisk (*) were grubbed in earlier years because productivity was not adequate (average well under 2 kg per tree) or because of other short-comings. Of the four remaining cultivars Gustav's Zeller was the most productive. Averaged for the years 1985-1989, a measure for precocity, the yield was 1.67 kg per tree and for all bearing years (1985-1995) as high as 3.81 kg. For Lang Tidlig Zeiler these values are 1.67 and 2.96, for Butler 2.15 and 2.80 (up until 1994), and for Negret 0.53 and 1.89.
Table 7. Kg/tree good nuts hazelnut-cultivar trial planted spring 1982 (4.5 x 2.75 m).
Cult. '85 '86 '87 '88 '89 '90 '91 '92 '93 '94 '95
GZ 1.09 2.29 0.51 1.06 3.41 0.90 5.80 5.67 5.37 4.65 11.12 LT 1.74 4.09 0.42 0.12 1.99 0.09 7.94 4.95 2.41 2.73 6.06 NE 0.95 0.58 0.00 0.13 0.98 0.12 3.83 6.22 4.19 0.36 3.48 TO 0.00 0.02 0.00 0.00 0.38 0.04 0.79 2.02 1.80 0.34 1.31 BU 3.13 1.03 1.50 0.83 2.15 0.78 4.96 5.15 6.83 1.65 *
ID 0.94 0.08 0.21 0.31 2.44 0.33 4.68 3.60 * PA 0.07 0.12 0.00 0.00 1.32 0.13 3.19 2.39 * WP 0.55 1.25 0.19 0.96 2.46 0.19 3.42 3.21 * WF 1.29 0.80 0.00 0.31 1.23 0.08 3.62 1.64 * WI 0.87 0.97 0.00 0.17 2.96 0.05 4.72 1.30 *
EN 0.69 0.47 1.29 0.66 1.34 0.59 2.95 * FC 0.02 0.02 0.17 0.30 1.20 0.23 1.82 * DA 0.81 1.29 0.25 0.50 1.48 0.20 * GA 0.43 0.95 1.37 0.16 1.19 0.09 * HZ 0.39 0.15 0.00 0.23 0.40 0.17 *
= trees grubbed 3Z = Gustav's Zeller; LT = Lang Tidlig Zeller; NE = Negret; TO = Tombul; 3U = Butler; ID = Istarski Dugi; PA = Palaz; WP = Webb's Prize Cob; WF = White Filbert; WL = Witpit Lambertsnoot; EN = Ennis; FC = Fertile de Coutard; GA = Garibaldi; RZ = Rote Zellernuß; DA = Daviana;
15 A.R. 1995 Research Station for Fruit Growing is the only one that can be recommended. Table 8. Kg/tree good nuts hazelnut-cultivar trial planted spring 1983 (4.75 x 2.42 m). Cultivar '89 '90 '91 '92 '93 '94 '95 Morell 1.43 0.34 5.15 2.55 8.22 0.55 10.18 Mortarella 0.57 0.18 3.35 2.98 2.08 0.60 11.04 Romai 0.55 0.38 4.38 4.45 4.15 0.81 6.58 Tonda Romana 0.75 0.21 1.48 3.54 2.46 0.15 11.18 Jemstegaard 5 0.37 0.45 0.73 * Lansing 0.43 0.24 0.28 * * = trees grubbed Hazelnut trial 1983 Table 8 summarizes the yields of the bearing years. It is obvious that production did not start until late (1989). Jemstegaard 5 and Lansing were grubbed because of low productivity. The remaining four cultivars proved productive, but not precocious. Morell gave on average 4.06 kg of good nuts per tree. Romai 3.04. Mortarella 2.97, and Tonda Romana 2.82. So, all surpassed the 2 kg level. Romai and Tonda Romana did not blanch well, the other two reasonably well and these two therefore warrant further testing. Hazelnut trial 1988 Table 9 gives the yields of the cultivars arranged in decreasing order of productivity. Table 9. Kg/tree good nuts hazelnut-cultivar trial planted spring 1988 (4.00 x 2.50 m). Cultivar '92 '93 '94 '95 Gem.* Tonda di Giffoni 1.77 2.65 1.20 3.45 2.27 Gustav's Zeiler2) - - 0.73 3.55 2.14 Camponica 1.40 1.04 1.09 3.50 1.76 Noccione 0.87 0.78 0.91 3.63 1.55 Pauetet 0.50 1.26 0.33 2.45 1.13 Casina1) 0.11 0.37 0.60 1.99 0.77 Tonda Gentile delle Langhe 0.47 0.62 0.11 1.65 0.71 Tombul Ghiaghli1) - 0.05 0.15 0.62 0.27 ) average 1992 to 1995, except when planted later. M planted spring 1990, 2) planted spring 1991. 16 A.R. 1995 Research Station for Fruit Growing 3ecause the planting years differ, this order is not completely fair up until now. So far, Fonda di Giffoni and (again) Gustav's Zeiler have proved ^uite productive. Kernels of Tonda di Giffoni blanch well, so this is a promising cultivar. rhe same is true in France where planting of this cultivar is increasing. rable 10. Kg/tree good nuts hazetnut-cultivar trial planted spring 1989 (4.75 x 2.52 m) Dultivar ^3 [94 JH5 Gern/ Emoa 1 0.16 0.87 5.57 2.20 ^iccia di Talanico 0.21 0.71 5.44 2.12 NRA H 105-28 0.58 0.60 3.19 1.46 moa 22) 0.02 0.40 2.77 1.06 mpériale de Trebizonde 0.45 0.29 2.00 0.91 vlontebello1) 0.00 0.17 2.41 0.80 :orabel 0.06 0.69 1.48 0.74 jmen1) 0.02 0.00 0.41 0.14 average 1993 to 1995, except when planted later. ) planted spring 1990, 2) planted spring 1991. Table 11. Kg/tree good nuts hazelnut-cultivar trial planted spring 1990 (4.75 x 2.52 m). Cultivar '93 '94 '95 Gern.* Emoa 31) 0.02 0.65 4.22 1.63 /Villamette 0.02 0.29 4.21 1.51 )SU 023-17* 0.14 1.07 3.04 1.42 )SU 039-44* 0.03 0.50 3.61 1.38 )SU 166-34* 0.04 0.45 3.20 1.23 )SU 167-02 0.00 0.18 1.54 0.57 'alaz 0.02 0.17 1.29 0.49 )SU 042-89* 0.00 0.00 1.04 0.35 ) average 1993 to 1995, except when planted later. M planted spring 1991. *) trees irubbed after harvest 1995; owner (Oregon State University) has withdrawn selection. lazelnut trial 1989 able 10 gives the productions so far obtained in this trial. Once again the cultivars are rranged in order of decreasing productivity. The Dutch selection Emoa 1 and the Italian ticcia di Talanico have already proved quite productive. The French INRA-selection H 05-28 also did well. All cultivars in this trial had good blanching indices. So, future 17 A.R. 1995 Research Station for Fruit Growinç 105-28 also did well. All cultivars in this trial had good blanching indices. So, future productivity will be decisive for the ultimate cultivar choice. Hazelnut trial 1990 Table 11 gives the production of the cultivars involved in this young trial. The first five cultivars all proved rather productive. In the meantime four cultivars from OSU (Oregor State University) have been withdrawn by the owner. These cultivars, marked in Table 11 with an asterisk, were not considered good enough. The kernels of the remaining two productive cultivars, Emoa 3 and Willamette, blanched well. Walnut (Juglans regia) S.J. Wertheim The results of the cultivar evaluation have been recently summarized in Fruitteelt 8£ (1995) 51/52, p. 40-41 to which paper the reader is referred. Table 12. Treevolume, production en average fruit weight of 14 quince cultivars Cultivar Treevolume (m3) Kg/tree Av.fr .weight ,(g ) autumn 1993 till 1995 till 1995 Agvambari 2.3 127 144 Bourgeault 1.7 102 126 Champion 2.1 22 196 Ekmek 2.0 109 301 Isfahan 1.3 35 199 Leskovacka 1.1 73 157 Limon 1.7 30 240 Ludovic 1.6 73 131 Portugal 1.4 13 218 Rea's Mammoth 1.9 129 260 Ronda 1.9 80 276 Serbian 1.5 39 194 Shams 3.7 64 242 Vranja 1.6 96 229 Quince (Cydonia oblonga) H. Kemp In the spring of 1988, a trial was planted with 14 quince cultivars, with maidens oi Quince MC at a planting distance of 4.75 x 2.05 meters. Three replicates with one trei per plot were planted. The experiment has a dual aim: obtaining winter hardy, goo< 18 A.R. 1995 Research Station for Fruit Growing ruiting quince cultivars, and obtaining winter hardy, weak rootstocks for pear. As a ;onsequence of the spring frosts of 1991, the quinces did not produce that year. From 1992 up to 1995, the production (Table 1) of some cultivars was (very) good. Agvam- )ari, Ekmek, Leskovacka, Ludovic, Rea's Mammoth, Ronda and Vranja are suitable for jrowing in The Netherlands. n the spring of 1993, four quince cultivars were planted, and in the autumn another our were added. With all cultivars, maidens on Quince MC were planted at a distance )f 3.50 x 2.55 m, with three replicates and one tree per replicate. In the spring of 1994, I/25 showed much dead bark, probably caused by winter frost of winter 1993/1994. Sobu has a drooping habit. In 1994, 1/18 and Morava produced the first Iruits. In 1995, all cultivars yielded (rather) well, especially 1/18, Morava and 1/21. i/lorava and Seker Gevrek have apple-shaped fruits and the others have pear-shaped ruits. fable 12. Tree volume, production and average fruit weight of 14 quince cultivars, PFW. :uitivar Tree volume (m Kg/tree Average fruit autumn 1993 until 1995 weight(g) until 1995 ^gvambari 2.3 127 144 tourgeault 1.7 102 126 'hampion 2.1 22 196 Ikmek 2.0 109 301 sfahan 1.3 35 199 eskovacka 1.1 73 157 .imon 1.7 30 240 udovic 1.6 73 131 'ortugal 1.4 13 218 iea's Mammoth 1.9 129 260 ionda 1.9 80 276 Serbian 1.5 39 194 ihams 3.7 64 242 'ranja 1.6 96 229 ruit-tree nursery research IJ. Wertheim and J. de Groene Iffect of benzyladenine on feathering of trees in the nursery i the Annual Report 1992 (p.78) a trial was described wherein buds of Rode Boskoop 19 A.R. 1995 Research Station for Fruit Growini on M.9 in the nursery were treated with branching agents. From 50 cm plant heigh onward, 50, 100, 200 or 400 mg/l benzyladenine (BA) was sprayed four or eight time weekly. Untreated buds and buds treated with 50 ml/l Promalin at 65 cm plant heigh were used as controls. The results of this trial have been summarized in Scienti Horticulturae 60(1994):31-39. In short, repeated sprays of BA induced feathering am the more so the more often it was applied and the higher the concentration (Table 13) The trees were planted in a commercial orchard in the spring of 1993 at 3.50 x 1.50 n for further evaluation. All trees grew well aided by drip irrigation. Table 13 shows tha 8 sprays of BA reduced flower-bud formation, but 4 sprays did not. Presence of flowe clusters in the planting year forms a point of discussion in practice. Some grower prefer flowers for a first crop in the planting season, others object, the presence c flowers, because it may spoil a good start and cropping in the following year. In 1992 a few apples were produced and in 1994 and 1995 a good crop was obtained due t good flower and fruit set. The trees with most feathers at planting produced most früh but the differences in kg between the treatments failed to be significant. In fruit numbe some differences showed up (Table 13). The results show that heavily-feathered appl trees can be successfully used. Table 13. Results branch trial Rode Boskoop 054 920221 Treatment Feathers Flower- 1994 + 1995 /tree clusters/ Kg/ Fruits 1992 tree 1993 tree /tree Untreated 4.2 a 10.9 cd 23.4 a 103.7 a Promalin 7.0 be 11.4 cd 24.5 a 101.0 a 4 x 50 BA 4.1 a 13.3 d 23.9 a 101.1 a 8 x 50 BA 4.8 ab 13.6 d 25.1 a 106.1 a 4 x 100 BA 7.3 c 14.8 de 27.0 a 118.7 a 8 x 100 BA 8.5 c 8.0 bc 23.7 a 113.2 a 4 x 200 BA 9.1 cd 19.3 e 26.0 a 110.9 a 8 x 200 BA 10.8 d 5.2 b 28.0 a 125.0 at 4 x 400 BA 11.0 d 11.0 cd 26.1 a 116.5 a 8 x 400 BA 15.0 e 0.2 a 31.8a 145.8 b F-test <0.001 <0.001 0.069 0.032 LSD 5% 2.2 4.8 n.s. 25.98 Values in 1 colomn followed by the same leter(s) do not differ significantly (P= 0.05). 20 A.R. 1995 Research Station for Fruit Growing Manting systems and light utilisation lanting systems with Jonagold, Fiesta and Elstar '.S. Wagenmakers, M. Tazelaar and J. Bootsma i spring 1991 a trial was planted with three cultivars on M.9 rootstock using four lanting densities (Table 1) and two locations (Wilhelminadorp and Zeewolde). At each ensity, the rectangularity of planting was varied, the ratio of distance between and /ithin the row being 1.5:1 (2:1 at 20,000 trees per ha) or 3:1. In addition, in the 3:1 ystems vertical and oblique trees (V-system with trees inclined to left or right alterna- ly) were compared. The angle of the V was smaller at higher densities. At Zeewolde, ees were planted normally (in), as well as on the soil. able 14. Production (1995 and accumulated for 1991-1995) Ibject Tonnes/ha 1995 Tonnes/ha 1991 1995 Jo-W Jo-Z Fi-W El-Z Jo-W Jo-Z Fi-W El-Z rees/ha 3.000 66 60 34 63 210 200 122 174 3.000 100 105 52 86 317 327 192 248 0.000 105 135 46 93 392 420 254 291 0.000 90 141 60 78 424 457 298 292 -test * * * * n.s. * # # * * * * * # * * * * * * SD 5% 22 22 - 12 34 41 30 27 inear n.s. * * * * n.s. * * * * * * * # * * * * luadratic * * * # * n.s. * * * * * * * * * * * * * * * rrangement ,5:1 96 103 44 76 356 362 217 231 :1 87 97 51 74 329 337 220 243 :1, V 87 114 48 80 323 343 212 243 ,5:1, on soil 113 84 351 257 :1, on soil 123 87 378 283 -test n.s. n.s. n.s. n.s. n.s. n.s. n.s. * SD 5% ------30 : Jonagold, Fi = Fiesta, El = Elstar, W = Wilhelminadorp, Z = Zeewolde. NS, *, * * differences within a sub-column not significant or significant at P < 0.05 or 0.001, spectively. (LSD) -: not calculated if F-test is NS. Linear and quadratic: trend. he production per ha increased generally with higher planting density. The influence of ee number was most pronounced in the range 3000-6000 trees per ha (Table 14). jrther intensification of density did not increase the production proportionally, since 21 A.R. 1995 Research Station for Fruit Growin; production levels at 20,000 trees per ha were in 1995 similar to or even lower thai those at 10,000 trees per ha. There were only slight differences in cumulative yield between the two highest densities. (Fiesta was in an off-year in 1995.) A higher production level was associated with a higher light interception (Table 15) However, an extremely high light interception (more than 80% of incoming light) di< not lead to more production. Trees at Zeewolde intercepted a little more light and frui production was slightly more fruit than those at Wilhelminadorp. Table 15. Light interception in 1995 (% van incoming light) Object Wilhelminadorp Zeewolde Trees/ha 3.000 63 65 6.000 73 82 10.000 85 85 20.000 89 93 F-test * * * # # * LSD 5% 4 6 Linear * * * * * * Quadratic * * * Arrangement 1,5:1 79 83 3:1 76 78 3:1 V 79 83 F-test n.s. n.s. LSD 5% - Wilhelminadorp 31 Aug. '95; Zeewolde 26 Sept. '95 (uniform overcast sky), n.s. differences within a sub-column not significant or significant at P < 0.001. (LSD) no calculated if F-test is NS. Linear and quadratic: trend. Table 16. Percentage of total production of fruits having more than 33% red blus! at a given light interception (percentage of incoming light), calculate per year and per arrangement. (Wilhelminadorp, 1993-1995) Arrangement 1,5:1 3:1 3:1 V Light int. '93 '94 '95 '93 '94 ' 95 '93 '94 '95 50 93 100 81 81 92 42 83 82 85 70 72 73 61 68 60 36 68 63 58 90 52 44 41 55 28 30 54 44 30 22 A.R. 1995 Research Station for Fruit Growing Statistical analyses of the results for fruit grading were not yet available for Zeewolde. :or Jonagold between 1993 and 1995, the percentage of high-quality fruit in the total iroduction decreased linearly with a higher light interception (Table 16). More than (0% of quality fruit (defined as more than 1/3 red blush per fruit) was produced at a ght interception of 50% or less. However, the production per ha was low. With 70% ght interception, about 70% of the fruit had sufficient red blush. That light interception vas realized in 1995 with 6000 trees per ha. In 1995, the 3:1-systems did not produce ufficient high-quality fruit. Even at a moderate level of light interception, the majority if the fruits had poor colour. System 1.5:1 System 3:1 50 60 70 80 90 100 % Light interception % Light interception System 3:T V-hedge Tonnes/ha >33% colour 50 60 70 80 90 100 % Light interception igure 1. Production well-coloured Jonagold (tonnes/ha fruit with more than 1/3 red blush) and light interception for three arrangements (Wilhelminadorp, 1993-1995) 23 A.R. 1995 Research Station for Fruit Growing There was practically no influence of rectangularity on light interception or production The 1.5:1 designs produced no more than 3:1 designs. The only significant effect was observed with Elstar trees planted on the soil in 3:1 designs, which produced more thar the other systems. However, the planting system had an effect on fruit quality. With the same light interception (70%), 1.5:1 designs produced about 15 tonnes more quality fruit than 3:1 designs, averaged for 1993-1995 (Fig. 1). The lower rectangulari- ties had a more uniform light distribution. The V-systems took an intermediate positior between 1.5:1 and 3:1. The optimum light interception with respect to fruit quality was 74%, 71%, and 73% for 1.5:1, 3:1 and V-systems, respectively. A light interceptior higher or lower than the optimum led to less quality production per ha. With the 1.5:1 designs, this decrease was more pronounced than with the 3:1 designs. The productior of quality fruit decreased with time. With the 3:1 systems, this decrease was strongei than with the other systems. In 1995, 3:1 systems produced on average 20 tonnes anc 10 tonnes less quality fruit per ha than 1.5:1 systems and V-systems, respectively. Light interception(% ) according to shadow spots uv + +/ A 80- / + /+ 60- + + 40- /+ 20- i i i i i 0 20 40 60 80 100 Light interception (%) according to lightmeters Figure 2. Comparison of measured and estimated light interception 24 A.R. 1995 Research Station for Fruit Growing 3efore harvest, light transmission was measured at fruit level (Jonagold, 1995, Wilhelminadorp). There was no clear effect of light on fruit size, but an increase of 10% ight led to 6% more red blush on the fruit. Shaded fruits tasted less good. Average taste estimates varied between 5.2 for fruits with less than 20% available light to 6.0 for fruits receiving more than 60% light. Taste was influenced by planting density only ndirectly, for fruits with more red blush tasted better than poorly coloured fruits. Shaded fruits had a more green background colour and were firmer than exposed fruits, thus showing a slower ripening. However, fruits of higher densities had a more yellow sackground colour, so they ripened faster despite the more shaded canopy, compared with the lower densities. This progress in ripening could be due to a higher leaf to fruit atio. At 20,000 trees per ha, the leaf to-fruit ratio was approximately double that of 3000 trees per ha. .ight interception was measured on a clear day (August 2, 1995) using two methods: jne with PAR meters recording light above and below the canopy, and the other by counting sun flecks on the ground on a representative area for each planting system along a 10 cm interval in a direction normal to the row from tree to tree in 4 replicates. A/hen "sun" and "shade" were estimated with 0 and 100, the average of all values yielded an estimated light interception. The comparison with the measured light nterception was fairly good (Fig.2) . Evaluation growth regulators S.J. Wertheim. J.M.T. Balkhoven-Baart and J.H. Bootsma 're-harvest-drop control Conference pear ï.J. Wertheim and J.M.T. Balkhoven-Baart To reduce pre-harvest fruit drop of Conference pear growers spray once or more with he synthetic auxin a-naphthyl acetic acid (NAA) shortly before picking. NAA raises the iuxin content of the fruits and as long as sufficient auxin decends from the fruits hrough the pedicels no abscission layer can be formed and no drop occurs. The future )f NAA is uncertain. Chemical firms do not like investing money in the renewal of equests for permission to use compounds in minor crops that do not give good returns, "herefore, a trial was carried out to establish whether pre-harvest drop control could be ichieved with GA3. The application of gibberellins to plants can raise their auxin :ontent. On eight-year-old trees of Conference on Quince MC rootstock ten treatments Table 17) were compared in a replicated trial with eight one-tree reps. Standard reatment was 10 mg/l NAA a.i. (Fruitone NA). GA3 was applied at 10 or 100 mg/l a.i. is Berelex once on 22 or 31 August (3 or 2 weeks before picking) or twice on both lates. Picking was carried out on 12 and 15 September (four reps per date) when :onsiderable drop had already occurred. Table 17 shows that NAA suppressed drop veil. There were no significant differences following the application of one or two prays nor between early or late application. GA3 had no significant effect on pre- iarvest drop, so it can not be an alternative for NAA. The chemicals had no effect on ruit quality after storage in a normal cool room (1°C) until 8 February 1996. 25 A.R. 1995 Research Station for Fruit Growinc Table 17. Results of pre -harvest-drop trial 137-9517 with Conference Treatment Spray Fruits/ Kg/ Fruit- Drop fruits/ date tree* tree weight(g) tree % Untreated 123.8 a 21.0 170 a 35.1 c 28.8 c Sprayed once NAA 10 mg/l 22-8 117.1 a 19.5 168 a 6.0 a 5.2 a GA3 10 mg/l 22-8 114.1 a 20.1 177 a 25.9 be 23.0 be GA3 100 mg/l 22-8 108.9 a 18.1 169 a 23.9 b 21.6 be Sprayed once NAA 10 mg/l 31-8 135.6 a 21.8 163 a 13.0 ab 9.0 a GA3 10 mg/l 31-8 111.4 a 19.7 179 a 21.9 b 20.2 b GA3 100 mg/l 31-8 114.8 a 19.7 173 a 23.9 b 20.8 b Sprayed twice NAA 10 mg/l 22.31 -8 116.9 a 18.7 161 a 8.1 a 6.4 a GA3 10 mg/l 22.31 -8 115.9 a 20.3 177 a 26.8 be 22.2 be GA3 100 mg/l 22.31 -8 123.4 a 19.2 160 a 26.9 be 23.1 be F-test 0.53 0.149 <0.001 <0.001 LSD 5% n.s. n.s. 9.90 8.09 Values in 1 colomn followed by the same letter(s) do not differ significantly (P= 0.05). Evaluation of GA4-rich mixture for russeting control S.J. Wertheim and J.M.T. Balkhoven-Baart In 1995, a new mixture of the two gibberellins A4 and A7 containing 80% of the forme and 20% of the latter GA was compared with the standard Berelex A4/A7 whicl contains 50% of each gibberellin. The new mixture was obtained from Fine Agrochemi cals Ltd, Worcester, England. GA4 is considered harmless to flower-bud formation whereas GA7 does suppress it. Six-year old Elstar trees on M.9 were used in the trial ii which six treatments (Table 18) were compared with eight one-tree reps. As usual fou sprays were applied with either 5 or 10 mg/l a.i. with both mixtures. Spraying dates were 8, 16, 26 May and 2 June; the first application was made 5 days after full bloom Table 18 shows that there were no differences in yield, fruit weight or percentage firs pick, but there were in fruits/100 flower clusters and skin russeting. Although all GA treated trees had less flower buds in 1996 than the untreated trees, differences wer not significant. The results indicate that in all aspects the new mixture was equal to th standard one. 26 A.R. 1995 Research Station for Fruit Growing Table 18. Results of gibberellin trial 137 95018 with Elstar Treatment ppm Fruits/ Fruits/ Fruit Class Russet Flower tree 100 weight(g) 1(%) # index* clusters/ clusters t. 1996 Untreated 166.4 a 101.3 a 131 a 49.3 a 409 a 128.1 a GA50/50 5 158.9 a 85.0 b 135 a 66.2 b 367 b 108.5 a GA50/50 10 144.4 a 81.9 b 137 a 66.9 b 367 b 80.3 a GA80/20 5 153.5 a 91.7 ab 129 a 60.6 b 379 b 94.1 a GA80/20 10 149.9 a 84.1 b 133 a 67.1 b 367 b 96.3 a F-test 0.2 0.02 0.5 0.001 0.004 0.14 LSD 5% n.s. 12.23 n.s. 8.95 24.28 n.s. weight percentage non and slightly russeted fruits. *) sum of the weight percentages non, slightly, moderately and severely russeted fruits times 1, 3, 5 respectievelijk 9. Values in 1 colomn followed by the same letter(s) do not differ significantly (P= 0,05). Evaluation of auxin-protein conjugates for rooting of cuttings S.J. Werthei m Under the guidance of the institute AB-DLO at Wageningen a new auxin-protein conjugate was tested for root formation on summer cuttings from a range of fruit crops. Compared to the standard treatment with the auxin IBA no improvement in root formation was obtained with the new compound. The research is being continued. Growth control with a retardant J.H. Bootsma n 1993, branched Elstar trees were planted at 3.00 x 0.90 m on ridges in the experi mental garden at Zeewolde. In 1994 and 1995, parts of the trunk or vertical leader were smeared with NAA in a carrier of Topsin M past. The treatments are given below. In 1994 smearing was done on 19 May, in 1995 on 30 May. All trees were chemically thinned with 0.15% of a 50% WP of carbaryl on 1 June. Table 19 gives some results from 1994 and 1995. Two treatments in 1994 (treatment 4) induced smaller fruits compared to the other treatments. Trees from this treatment grew the least of all. In 1995, growth reduction was obtained again by the use of some treatments. Untreated trees required 52 pruning cuts totalled for 1994 and 1995. Trees of treatments 4 and 6 required 42 cuts and the other treatments required intermediate numbers of cuts. Although these differences seem small the reduction in labour may be considerable. However, it is possible that fruit size suffers from such treatments. It appeared that the bark of two-year-old parts takes up more NAA than that of three-year-old parts. 27 A.R. 1995 Research Station for Fruit Growing Treatment (%NAA a.i.) growth-control trial Elstar 076 94063 Zeewolde 1. Untreated 2. 2% on trunk*) in 1994 only (three-year-old part) 3. 1% on vertical leader*) in 1994 only (two-year-old part) 4. Treatment 2 + 3 5. as 2 + 2% vertical leader in 1995 (three-year-old part) 6. as 3 + 1% vertical leader®) in 1995 (two-year-old part) 7. as 1 + 2% or 1% vertical leader in 1995 (three and two-year-old parts respectively) *) from union 20 cm around trunk. *) from lowest side branches 20 cm around vertica leader. @) higher up vertical leader Table 19. Results of NAA trial 076 94063 Elstar Zeewolde Tr. Flower- Fruits/ Fruits/ Kg/ Fruit Growth/ %kg ment clusters/ tree 100 tree weight(g) tree (m) >70 /tree clusters (mm) 1994 1. 191 79 42 11.2 144 7.4 70 2. 179 86 49 12.1 142 5.9 71 3. 182 84 47 11.5 137 6.0 69 4. 183 82 46 10.7 133 5.3 55 5.M 182 78 44 11.2 142 6.4 6.2) 183 81 45 11.6 142 5.8 7.3) 184 82 46 11.2 138 6.3 1995 1. 80 119 185 19.0 161 13.6 2. 82 137 184 19.8 155 12.6 3. 80 147 190 19.8 140 10.6 4. 79 127 173 17.8 150 11.3 5. 78 136 184 19.6 146 13.1 6. 90 150 177 20.3 137 9.2 7. 68 122 183 17.6 146 10.2 ) still equal to treatment 2; ) ditto to treatment 3; ) ditto to treatment 1 Pruning and tree shapes J.M.T. Balkhoven-Baart Growth control Conference In 1994, a trial was planted in Wilhelminadorp to compare the effects of variou: 28 A.R. 1995 Research Station for Fruit Growing growth-control methods on vegetative growth, productivity, and fruit quality with Conference pear on Quince MC rootstock. The plant material was two years old and well branched. The planting distance was 3.00 x 1.25 m. The growth-control methods were: root pruning, application of chloromequat (CCC) or ethephon, and trunk smearing with a-naphthyl acetic acid (NAA). The latter two treatments have no clearance for practical use. All treatments were applied in 1995 either alone or in combination. Table 20 gives some application data. Trees treated with ethephon and/or NAA had a lighter leaf colour during the summer. The effects of the main four treatments are given in Table 20. Root pruning reduced growth and fruit size but not productivity. CCC only affected vegetative growth. Table 20. Applica tion data of growtl l-control trial 083-WI9412. Treatment Date Temp. RH Wind Conditions/details (°C) (%) (m/s) Root pruning (1x two 04/04 10 80 4-5 knife angle 20° row sides, 40 cm from trunks, depths 40 cm) CCC (2x 1000 ppm 02/05 20 40 3.5 sunny a.i. with Luxan ~CC 400 g/l) 11/05 11 70 3.5 partly cloudy Etephon 03/05 30 40 3.5 sunny, pear 0 4-5 mm [3x 120 ppm a.i. with Ehtrel A 480 g/l) 15/05 19 50 6 partly cloudy, pear 0 8-10 mm 24/05 25 60 5 sunny MAA 02/05 20 40 3,5 sunny, 20 cm around trunk 1x Topsin M paste on from union with 1.3 ml/ :runk with 2% NAA tree with Fruitone NA 100 g/D Ethephon and NAA did not reduce vigour but caused fruit thinning leading to lower productivity. The highest productivity was obtained after CCC application or root pruning (8.1 and 8.5 kg/tree respectively). The combination of ethephon with NAA, whether or not combined with the other two treatments, gave the lowest production 4.6 kg). The lack of growth reduction by ethephon and NAA was probably due to their ruit thinning effect. Following treatments with ethephon, even more shoots were produced per tree when compared with untreated trees. The growth reduction caused }y root pruning and CCC spraying was equal, but unlike root pruning, CCC had no îffect on average shoot length. When root pruning and CCC were combined the greatest growth reduction was obtained. In 1996 the treatments will be repeated. 29 A.R. 1995 Research Station for Fruit Growing Fruit quality, orchard and climate Influence of light on fruit quality for four rootstocks P.S. Wagenmakers and M. Tazelaar Vegetative growth and fruit quality of Jonagold on four rootstocks were measured (Table 22). The tree volume and production per tree of P 16 were similar to those o1 M.9. However, P 16 had slightly less colour. P 22 had a considerably smaller tree Table 21. Results 1995 growth-control methods on Conference in trial 083- WI9412 Fruits/ Kg/ Fruit Shoot tree tree weight (g) length 1995 m/tree Root pruning - 29 6.0 215 a 13.1 a + 31 6.3 207 b 8.9 b F-test n.s. n.s. 0.037 <0.001 CCC - 29 6.0 211 12.8 a + 31 6.3 211 9.2 b F-test n.s. n.s. n.s. <0.001 Etephon - 34 a 6.7 a 209 10.8 + 26 b 5.5 b 213 11.2 F-test 0.002 0.003 n.s. n.s. NAA - 35 a 6.9 a 204 a 11.5 + 25 b 5.3 b 218 b 10.6 F-test <0.001 <0.001 <0.001 n.s. n.s. = not significant. Within treatment values in 1 colomn folllowed by the same lette do not differ significantly (P= 0.05). volume and production than M.9, and this was associated with more well-colourec fruits. Ottawa 3 grew slightly more vigorously than M.9 but the production was less whereas the percentage well-coloured fruits was slightly less than that on M.9. Th< light availability was measured in the proximity of a fruit on a cloudy day shortly befor« harvest. Incoming light was taken for reference. The relationship between ligh exposure and fruit colour was approximately the same for all rootstocks (Fig. 3). Abou 30 A.R. 1995 Research Station for Fruit Growing 10% light transmitted to the fruit (thus local light interception was 60%) was sufficient or a minimum of 33% red blush. Light shortage seemed to have a slightly stronger îffect on M.9 than on the other rootstocks. When less than 20% light was available, or example, there were practically no coloured fruits on M.9, whereas fruits on P 16, P 12, and Ottawa 3 still had some colour. "he fruits on P 22 were firmer, had a more yellow background colour, a lower starch ind higher sugar and acid content, and a higher dry weight (Table 23). Whether this was a rootstock effect, is doubtful, however, because crop load in 1995 was markedly ower than on the other rootstocks, and this in itself can lead to earlier ripening. % red blush\fruit % red blush\fruit ' UJt + nt • *0- . M- •t • • + + + + + ' * + + ++ + + 00- M- + + ; + + + + + .'.'.y + +++ + ++ + ++ + + * + 40- + + «- + + ++ + + + + + : ' ..' + + -H- + -H- + M- M- * ++++ 4+ ++ +++ + + -H--H-+4+ * -t-H-H- 1 ill lUIl I II III 1 — .—..—. +-H f +++ 0 »0 40 M M K» < ) 20 40 M M 100 % light/fruit % light/fruit % red blush\fruit % red blush\fruit * TZZ • Oï to l to- M x x K M " • m mm m X il M x m K m m to- M x to- • xx M mm m * MM* X XXX X - m m KM * m x M 40- MM MX X MXX 40- • • ME M X X » MM» KW K X «KM K K M 20- mm K ÏO- • M • • • MM KM • • m m • • KK KM K KM» KM K • •• M • • • • • M 40 M M 1 M » 20 4« M M 100 % light/fruit % light/fruit :igure 3. Percentage of production with more than 33% red blush related to light availability per fruit with four rootstocks (Jonagold, Wilhelminadorp 1995) 31 A.R. 1995 Research Station tor Fruit Growinç Table 22. Production per tree (1995 and accumulated), relative distribution ir colour grades (1995) and tree volume (autumn 1995) for Jonagold Wilhelminadorp. Kg/tree Kg/tree Percentage kg red blush Volume 1995 1990-'95 <10 10-33 >33 m3/tree M.9 29.3 159 37 31 32 1.03 P16 31.2 156 41 34 25 1.00 P22 16.1 107 20 27 53 0.48 Ottawa 23.8 126 44 28 28 1.22 Table 23. Firmness, background colour, starch, sugar, acid, percentage dry mattei (Jonagold, Wilhelminadorp, 1995). Firm, backgr. Starch Sugar Acid % dry m M.9 7.3 -14.1 9.1 13.2 0.59 15.1 P1 6 7.4 -14.3 9.3 12.7 0.56 14.5 P2 2 7.8 -10.9 8.8 14.5 0.61 16.5 Ottawa3 7.3 -14.5 9.0 13.4 0.59 15.2 Pruning and thinning with Elstar P.S. Wagenmakers and H. de Putter A trial was established on full-grown Elstar on a commercial fruit holding to study the effect of crop load on fruit quality at different light levels within the tree, the lattei being created by either normal, intensive, or no winter pruning at all. No summei pruning was done. Flower thinning was carried out by removing two thirds of the clusters. After June drop, all clusters, including those of unthinned trees, were set tc one fruit. The unpruned, unthinned trees, having the highest light interception, achieved the highest production (Table 24). Light penetration into the trees was, however, so poo that size and colour were insufficient. Thinning of unpruned trees improved the leaf-frui ratio and hence the fruit size, but did not improve the colour. Pruning and thinning lee to a lower production. Fruit weight of normal and intensively pruned trees was approxi mately the same. Fruit thinning had no effect on fruit size when trees were pruned; 8( mm seemed to be about the maximum size in this trial. However, there was a positive effect of thinning on colour, which was more pronounced in the intensively-prunec trees than in the normally-pruned trees. The unpruned, unthinned trees were harvested one week later than the other trees, anc this has influenced several parameters of ripening. Therefore, the effect of thinning ha! 32 A.R. 1995 Research Station for Fruit Growing :o be limited to observations on the pruned trees. Flower thinning had no significant sffect on firmness on the pruned trees, but fruits of unpruned trees were slightly firmer :han those of pruned trees. A heavy crop load decreased the ripening process, as was seen with a more green background colour and a lower starch estimate for unpruned or jnthinned trees. In addition, unpruned trees produced more sour fruits with a lower sugar content than pruned trees. Thinning made fruits sweeter as well as more sour. -ruit size is an important parameter to determine fruit quality. The potential fruit size in 3 given season depends on weather and orchard characteristics such as the leaf-fruit atio. A physical-physiological model has been developed to quantify total apple >roduction per ha on the basis of light interception and gross and net canopy photosyn- :hesis. This model has been extended by simulating the daily growth of individual fruits. l"o calculate canopy photosynthesis, the model makes use of daily weather data radiation and temperature). Growth of vegetative tree parts and fruits is simulated. :inal fruit size (in mm) and the distribution of fruits over three quality grades is calculated as a function of time and intensity of thinning. The model is suitable for Elstar, Jonagold, and Golden Delicious. fable 24. Production and fruit quality in crop-load experiment with Elstar (1995) 'runing No Normal Heavy Thinning -(*) + -^ + - +*) *\ Cilo/tree 15.7 13.2 11.4 7.7 10.4 6.1 :ruitweight(g) 135 156 179 191 180 196 Diameter (mm) 72 76 79 82 80 80 'ercentage <10% blush 50 58 58 59 46 24 Percentage 10-33% blush 21 19 21 11 19 27 'ercentage >33% blush 29 24 21 30 35 50 :irmness (kg) 6.3 6.8 6.3 6.4 6.4 6.3 ireen background colour -13.0 -12.0 -8.9 -7.4 -8.9 -6.5 tarch estimate 4.4 3.3 5.0 5.6 4.8 4.9 îugar (% brix) 12.0 11.4 12.4 13.0 13.0 13.5 \cid 0.74 0.88 0.91 0.96 0.91 1.00 ') harvested one week later than other treatments Simulation of fruit growth during the season *.S. Wagenmakers and A.D. Hartkamp ruit size is an important parameter to determine fruit quality. The potential fruit size in given season depends on weather and orchard characteristics such as leaf-fruit ratio. v physical-physiological model has been developed toquantity total apple production ter ha on the basis of light interception and gross and net canopy photosynthesis. This 33 A.R. 1995 Research Station for Fruit Growing model has been extended by simulating the daily growth of individual fruits. Tc calculate canopy photosynthesis the model makes use of daily weather data (radiatior and temperature). Growth of vegatative tree parts and fruits is simulated. Final fruit siz« (in mm) and the distribution of fruits over three quality grades is calculated as E function of time and intensity of thinning. The model is suitable for Elstar, Jonagold anc Golden Delicious. Black skin discoloration in pear S.J. Wertheim and J.M.T. Balkhoven-Baart Skin discoloration in the cooking pear Gieser Wildeman can be a problem, resulting ir down-grading of the fruit. For more information the reader is referred to a paper ir Fruitteelt 85 (1995) 17: 20-21. Earlier research showed that the fewer pears per tree the higher the number of fruit with skin discoloration. In addition, it appeared that fruit Table 25. Results of black-skin discoloration trial Gieser Wildeman 128-1 WI95103 Treat Ca* Flower Fruits/ Fruits/ Kg/ Fruit Flower ment dus - tree* 100 tree weight clusters/ ters/t. flower (g) tree 1995 clusters 1996 Untreat. 919 a 723 a 78.7 b 42.3 ab 61 a 32 a + 946 a 723 a 76.8 b 46.4 a 65 a 24 a _ GA3 871 a 658 a 76.7 b 43.4 a 66 a 28 a + 869 a 613 a 77.1 b 38.5 abc 64 a 56 a 1fruit / _ 906 a 384 b 41.9 c 35.0 bc 94 b 144 ab 2clusters + 922 a 370 b 40.1 cd 31.2 cd 84 b 63 a 1fruit / - 910 a 214 c 23.7 de 24.6 de 117 c 244 b 4clusters + 855 a 214 c 25.3 de 24.7 de 117 c 233 b 1fruit / _ 883 a 120 c 13.7 e 16.3 f 137 d 406 c 8clusters + 932 a 117 c 12.5 e 15.9 f 140d 467 c Untreat.1 - 223 b 200 c 98.7 a 22.3 ef 111 c 663 d F-test <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 LSD 5% 168.4 129.3 16.52 8.25 13.5 137.4 *) - = without, + = with calcium sprays. *) pre-harvest drop. M Trees with low numbers of flower clusters. Values in 1 column followed by the sam< letter(s) do not differ significantly (P = 0.05). 34 A.R. 1995 Research Station for Fruit Growing with skin discoloration had a lower calcium content than sound fruit (see Annual Report 1994: p.33-35). In 1995, a trial was carried out in which fruit numbers per tree vere varied by spraying GA3 (gibberellic acid) or by hand thinning and fruit-calcium tontent was raised by applying sprays of calcium nitrate. Eleven treatments (Table 25) vere compared on mature trees on Quince MC rootstock planted at 3.00 x 2.50 m. ipraying with 15 ppm GA3 was done on April 12 and hand thinning to 1 fruit per 2, 4 ir 8 clusters was carried out on 6 and 7 June. Eight sprays with Ca(N03) were made rom 9 June every two weeks, the last one on 12 September. Harvesting was carried out 9 September. )uring the whole season fruit samples were brought to the Plant Cytology and Morpho- ?gy Laboratory of the Agricultural University at Wageningen for anatomical analyses, 'his work will not be dealt with here. 'able 25 summarizes data on flowering and fruiting and Table 26 on the skin disorder nd shows that GA3 did not increase fruit set, probably because the set was already igh. Not surprisingly, thinning reduced fruit numbers and the more so the greater the hinning. Trees that had only few flower clusters had a level of fruiting about equal to hat of well flowering trees thinned to 1 fruit per 4 flower clusters. Per 100 flower usters the former trees had the highest set of all treatments. GA3 had no effect on ruit size but thinning exerted a great influence. Fruit size increased, the greater the hinning. Thinning reduced production, so the loss in fruit number was not compensa- ed for by the increase in fruit size. Pre-harvest drop increased with the number of fruits er tree (data not given). Flower-bud formation was enhanced by hinning and the more so the greater the thinning. GA3 had no effect on return bloom. Jnthinned trees and those treated with GA3 had a very poor return bloom in 1996. rees thinned to 1 fruit per 2 clusters still had inadequate flowering, but trees thinned lore heavily had a reasonable to good bloom intensity. All trees that produced few ower clusters in 1995 showed abundant bloom in 1996. Calcium application had either an effect on the characters mentioned nor on the calcium content of the fruit, lalcium content decreased noticably with decreasing fruit numbers per tree. U harvest, black-skin discolorations only occurred on trees that had not many flower lusters in 1995. However, grading at the end of December (data not given) or at the nd of January showed that black skin occurred in all treatments (Table 26), but was nly of significance after thinning to 1 fruit per 8 flower clusters and even more so on ruit from the trees with few flower clusters. Apparently, black skin increased during old storage (at 1° C). Possibly, the disappearance of chlorophyll in the skin played a art by increasing the visibility of the disorder. ;o indeed, black-skin discoloration mainly occurs in trees that have low fruit numbers, urther it appears that timely thinning to 1 fruit per 4 clusters gives a useful result by ombining a reasonable fruit size with relatively little black skin and a fairly good return loom. It makes sense to separate fruit from poorly and good cropping trees at harvest a reduce grading problems later on. 35 A.R. 1995 Research Station for Fruit Growini Table 26. Results of black-skin discoloration trial Gieser Wildeman 128-WI95103 Treat Ca* % vr. Weight perc. fruit Black Calcium- ment with with black skin5 index* content black 29-01-1996 fruits skin mg/100 g' harvest 1 2 3 4 5 Untreated 0.8 a 91 8 1 0 0 118 a 15.0 ~+ 0.6 a 91 9 1 0 0 118 a 12.8 GA3 0.5 a 89 10 0 0 0 122 a 12.4 + 0.3 a 94 5 1 0 0 114 a 14.2 1 fruit/ 1.0 a 89 10 1 0 0 122 a 10.1 2 clusters ~+ 1.3 a 91 9 1 0 0 119 a 9.7 1 fruit/ 1.4 a 86 12 1 0 0 129 a 9.8 4 clusters + 1.7 a 86 14 1 0 0 131 a 9.7 1 fruit/ 0.4 a 67 23 6 3 2 195 b 8.2 8 clusters ~+ 1.7 a 66 30 4 1 0 179 b 8.6 Untreated1 17.3b 49 30 9 3 2 243 c 8.0 F-test <0.001 <0.001 LSD 5% 6.58 44.5 = without, + = with calcium sprays. M Trees with low numbers of flower clusters. E) 1 = no, 2 = light, 3 = moderate, 4 = severe, 5 = very severe black-skin discoloration. *) sum of weight% (no x 1)+(ligh t x 3) + (moderate 5) +(severe x 7) +(very severe x 9). ) on fresh weight basis October 1995. Values in 1 column followed by the same letter(s) do not differ signifi cantly (P = 0.05). Chemical thinning S.J. Wertheim, J.M.T. Balkhoven-Baart and J.H. Bootsma Evaluation of new thinning compounds on apple S.J. Wertheim and J.M.T. Balkhoven-Baart In 1995, two new thinning compounds, each in three concentrations, were tested o mature trees on M.9 rootstock of Rode Boskoop, Elstar, Golden Delicious, and Jone 36 A.R. 1995 Research Station for Fruit Growing old. The chemicals were the flower thinner TD2337-2, based on endothallic acid from :lf-Atochem, Vondelingeplaat and the fruit thinner D4017 from Luxan, Eist with lenzyladenine as the active ingredient. These chemicals have not been given approval or practical use. Table 27 lists the treatments involved; with Elstar all 15 treatments were used, with the other cultivars only the first ten treatments. All sprays were applied vith a knapsack sprayer until the point of dripping. The treatments were replicated ight or seven (Jonagold) times in randomized block designs with one tree per plot, 'lanting distances were 3.00 x 1.25 m (Rode Boskoop and Elstar), 3.25 x 1.25 m Jonagold), and 3.25 x 1.30 m (Golden Delicious). Per tree between 0.4 and 1 I spray quid was used, depending on cultivars and time of application. Spraying conditions are iven in Table 28. The combination of carbaryl and GA4+7 was applied as a tank mix, ne combination carbaryl and D4017 separately, the latter was applied first. TD 2337-2 able 27. Treatments thinning trials 137-WI95019 1. Untreated 2. Hand thinned 3. D4017 0.047% + 0.1% Tween 20 at 1 2 mm fruit old wood %. D4017 0.094% + 0.1 % Tween 20 at 1 2 mm fruit old wood 5. D4017 0.188% + 0.1% Tween 20 at 1 2 mm fruit old wood 3. TD2337-2 0.05% at 80% open flowers 7. TD2337-2 0.10% at 80% open flowers 3. TD2337-2 0.20% at 80% open flowers 3. Amid Thin 0.075% at end of flowering old wood 0. Carbaryl 0.15% at 12 mm fruit old wood 1. Berelex A4/A7: 0.40% at 12 mm fruit old wood 2. Treatments 4+10 3. Treatments 4 + 11 4. Treatments 10 + 11 5. Treatments 4+ 10 + 11 imid Thin: 63 mg/l a.i. NAAm = 75 g/100 I water larbaryl: 750 mg/l a.i. carbaryl = 150 g/100 I water erelex A4/A7 : 40 mg/l a.i. GA4+ 7 = 400 ml/100 I water ween 20 wetter: 0.10% = 100 ml/100 I water aused burning of the petals, the more so the higher the concentration. The highest oncentration also caused some damage on those leaves present during spraying. Elstar ees looked thinner in leaves during the whole season after the use of both highest osages. The other compounds were harmless to the trees. he thinning action can be derived from the fruits per 100 flower clusters and the fruit /eights given in Table 29. 37 A.R. 1995 Research Station for Fruit Growin< Table 28. Spraying conditions Treat Date Temp. %RH Wind/sun- Remarks ment °C data Rode Boskoop 6,7,8 28/04 22 50 NNE3 70-80% open flowers sunny/partly old wood, red bud till cloudy balloon stage 1-year-old wood slow drying 9 05/05 31 45 E2 sunny, end bloom of old wood, clear sky just before full bloom 1-year-ok wood, slow drying 3,4,5,10 26/05 26 60 NE3, slightly fruit Golden Delicious 6,7,8 29/04 14 58 ZZE3-4, full bloom 1 May, slow drying clouds, very slight 9 08/05 20 53 NW5-6 rapid drying partly cloudy 3,4,5,10 26/05 27 65 NE3 fruit cp old wood 11.7 and 1- clear sky year-old wood 6.7 mm slow drying Jonagold 6,7,8 28/04 20 50 NNE3, 60 till 80% full bloom, 1-year slightly -old wood till balloon stage, cloudy slow drying 9 05/05 25 52 E2 end of bloom old wood,jus before full bloom 1-year-oh wood, slow drying 3,4,5,10 26/05 23 67 NE2-3 fruit 38 A.R. 1995 Research Station for Fruit Growing rable 29. Resultats thinning trials 137-WI95019; A = fruits/100 flower clusters1, G = average fruit weight (g) at harvest. IO. Rode Boskoop Elstar Golden D Jonagolc A G A G A G A G 1. 67.0 a 159 a 91.9 a 118 a 164.1 a 92 ab 79.1 a 160 a 2. 61.0 ab 175 bed 58.6 fg 143 cde 95.6 f 122 e 62.4 b 186 bed 3. 63.0 ab 182 d 81.2 abc 124 ab 131.0 cd 101 bc 75.3 ab 179 abc 4. 58.8 abc 180 cd 81.1 abc 117 a 118.9 de 114 de 62.3 b 205 d 5. 50.8 c 206 e 66.5 efg 143 cde 107.1 ef 119e 67.8 ab 187 bed 6. 60.4 abc 162 ab 78.1 bed 123 ab 157.2 ab 89 a 81.5 a 162 a 7. 66.3 ab 168 abc 74.2 cde 119 ab 144.8 bc 10Q bc 77.5 a 170 ab 8. 56.3 bc 177 cd 56.7 g 139 cd 148.3 b 104 cd 67.7 ab 164 a 9. 66.4 a 173 bed 87.3 ab 114 a 150.2 ab 97 abc 78.8 a 167 ab 0. 64.1 ab 177 cd 84.2 abc 122 ab 131.0 cd 103 cd 68.0 ab 191 cd 1. 86.6 ab 114a 2. 63.9 efg 152 de 3. 68.8 def 138 c 4. 68.9 def 132 bc 5. 45.2 h 155 e 0.047 <0.001 <0.001 <0.001 <0.001 <0.001 0.038 <0.001 ISD* 10.08 13.8 11.29 13.9 15.37 10.4 14.06 20.6 ) with Elstar and Jonagold corrected for differenence in number of flower clusters by nalysis of covariance. *) F-test; *) bij 5%. Values in 1 colomn followed by the same 3tter(s) do not differ significantly (P= 0.05). JodeBoskoop )nly the highest concentrations of both compounds thinned significantly. Fruit weights vere higher following most treatments except after spraying with 0.05% and 0.10% D2337-2. Possibly, the early leaf damage played a part here, which was apparently lore than compensated for by the thinning action of the highest concentration. The ffect on fruit size without a thinning effect of a number of treatments can not be roperly explained. The thinning compounds did not have any effect on fruit russeting r firmness. '/star Jl TD2337-2 treatments had thinned before June drop with the greatest effect from ne highest dosage. Although quite a number of treatments had a thinning action, with 39 A.R. 1995 Research Station for Fruit Growinc respect to fruit size (about 150 g/fruit) this was only adequate in the case of treatment; 5, 8, 12, 13, and 15. Neither Amid Thin, carbaryl nor Berelex A4/A7 thinned. With regard to the production of fruits larger than 70 mm in diameter only treatments 5 anc 13 were equal to hand thinning and treatment 12 was even better. All other treatment: were inadequate. None of the treatments caused skin russeting. Fruit firmness on the chemically thinned trees was equal to unthinned or hand thinned; the latter havinc slightly firmer apples. Only the apples from treatment 15 were significantly firmer thar from the other treatments. Golden Delicious Given the average fruit weights, all thinning treatments were inadequate even hanc thinning. However, except the lowest TD2337-2 concentration and Amid Thin al treatments did thin. Most thinning was obtained with both highest concentrations o D4017. There were no effects on russeting or firmness. Jonagold Given the fruit number per 100 flower clusters at harvest, based upon one branch pe tree, only the middle concentration of D4017 (treatment 4) did thin. When fruit numbe per tree is the criterion treatments 2, 4, 5, and 8 were effective. Except for treatmen 8, these treatments also produced larger fruit. The same held for treatment 10 Apparently, the branch unit did not adequately represent the thinning effect on th( whole tree. Treatments 5 and 7 induced some skin russeting. The work with TD2337-2 and D4017 will be continued. Early thinning of Elstar a necessity J.H. Bootsma Elstar is a biennial cultivar and therefore needs chemical thinning right from the earh years in the orchard. Even in the planting season trees can already have too man' flower clusters leading to an off-year in the second year after planting. Often howeve feathered snip or interstem trees do not have too many flowers and with good care certain production in the first year is possible. It is felt that in the second year chemicc thinning must be used in order to prevent an off-year in the next season. The next trie was carried out to obtain more information on this point. Trial 137 93026 in Zeewolde From 1993, the second year after planting, Elstar trees on M.9 planted at 3.00 x 1.0( m were thinned with either Amid Thin (NAAm) or carbaryl. In 1995, Amid Thin wa sprayed on 1 5 May and carbaryl either on 22 May (end of flowering), 29 May (fruitle diameter old wood 12 mm) or 6 June (fruitlet diameter one-year-old wood 12 mm). Fo comparison non-thinned and hand thinned trees were present. In 1995, 50% of th unthinned trees had an off-year, which was reduced to 33% by hand thinning alone an< 40 A.R. 1995 Research Station for Fruit Growing to 16% by chemical thinning plus additional hand thinning. This is not a satisfactory result and it shows how difficult it is to obtain a regularly bearing planting of Elstar. Table 30 shows some results of this trial. The action of carbaryl applied at the 12 mm stage on older wood was good. Together with additional hand thinning a gain of 6 kg per tree in the size class >70 mm was obtained compared with hand thinning alone. Compared to non-thinned trees the difference was even more striking. In the second year flower bud formation was stimulated to a greater extent by an application of carbaryl at the end of bloom rather than with applications at a later date. Table 30. Chemical thinning trial Elstar 137-WI93026. Start chemical Chemical thinning and hand thinning treatments 2nd leaf (1993) Treatment Kg per tree total 1993-1995 Hand thinning 1994- 1995 Total >70 mm >33% red Fr./tr. hours/ha Unthinned 39 18 31 0 0 Hand thinned 40 30 38 97 162 *\mid Thin 40 30 38 61 102 ;b end bloom old wood 38 31 36 50 84 :b 12 mm old wood 44 36 41 63 105 ;b 12 mm 1-yr- old wood 41 33 38 74 123 :b 2 x 12 mm* 42 33 39 61 102 ') fruitlets per tree thinned. *) cb (= carbaryl) at 12 mm average fruit diameter old wood and 1-year-old wood. Concentrations: Amid Thin 75 g/100 I and carbaryl 50% WP 150 3/100 I. Trial 137 95034 in Zeewolde n 1995, carbaryl (0.15% of a 50% wettable powder) was sprayed on Elstar trees on vl.9 at 3.25 x 1.25 m in their sixth leaf at different times (Table 31) in order to find a possible sensitive period. Only branches were treated and there were 11 reps per reatment. On two occasions (2 and 6 June) also 0.30% carbaryl was used in order to ;ee whether it makes sense to double the concentration, for Elstar does have a poor eaction to chemical thinners such as carbaryl. The number of fruits per branch were corrected with a covariance analysis for differences in number of flowers. Analysis of variance showed that there was only an indication for a time effect, with 16 to 25 days after full bloom being the sensitive period (Table 32). Regression analysis pointed to 20 Jays after full bloom as the most sensitive period. 41 A.R. 1995 Research Station for Fruit Growinc Table 31. Data trial 137-ZE95034 Elstar (see text) Treat- Spraying Day Clouds Tempera RH (%) ment date time ture °C 1. Untreated 2. 12/5 *) 15.30 heavy 12 58 3. 15/5 15.30 half 16 45 4. 18/5 15.30 half 11 72 5. 22/5 10.00 light 14 57 6. 24/5 16.00*) light 25 58 7. 27/5 10.00 half 18 74 8. 30/5 13.00 light 24 53 9. 02/6 16.00 light 15 85 11. 06/6 16.00 heavy 14 81 13. 12/6 15.30 half 16 72 *) end of bloom = 10 days after full bloom. #) directly after rain Table 32. Results of thinning trial 137-ZE950349 Elstar Treatment Date Carbaryl Fruits/branch *) no. concentration % 1. Untreated - 14.4 2. 12/5 *) 0.15 12.5 3. 15/5 0.15 12.7 4. 18/5 0.15 11.6 5. 22/5 0.15 10.7 6. 24/5 0.15 11.0 7. 27/5 0.15 10.1 8. 30/5 0.15 12.9 9. 02/6 0.15 13.0 10. 02/6 0.30 12.8 11. 06/6 0.15 13.8 12. 06/0 0.30 15.8 13. 12/6 0.15 13.3 F-test 0.064 *) end of bloom = 10 days after full bloom. **)from 50% WP. corrected for differen ces in number of flowers per branch by covariance analysis. 42 A.R. 1995 Research Station for Fruit Growing Planting trees on or in the ground J.H. Bootsma 3y planting trees in ridges, growth control seems to become feasible. In 1995, in the îxperimental garden at Zeewolde apple trees were planted in ridges for the fifth time. Fhe aim was to improve growth in the planting year in such a way that high production n subsequent years could be obtained facilitating growth control. . n a first trial in 1991, 3-K of Jonica on M.9 trees were planted in ridges at 3.00 x 0.50 n. This trial showed that such trees can grow better than traditionally-planted trees, er tree 1 m extra growth was obtained. The ridges consisted of potting soil covered by soil and mushroom compost. Fertigation is a necessity with such a way of planting. The jxtra growth seems to be induced by the good medium surrounding the roots. Possibly, he rapid warming of the soil in the ridges and the good water drainage also play a role, ndeed, in the second year ridge trees produced slightly more fruit. The higher position jf the union plus the slightly higher production lead to growth control. After four years, lowever, both tree types had equal growth (14 m/tree), but ridge trees produced 4 kg )er tree more than trees planted normally in the soil. n 1992, again a trial was carried out with Jonagold Decosta on M.9 with an interstem )f Dubbele Zoete Aagt planted at 3.00 x 0.50 m. In the planting year ridge trees grew m per tree more than traditionally planted trees, but in the second year 1 m less, ncluding 1995, ridge trees had a total growth of 28 m per tree accumulated for the hree years as against 27 m for the normally planted trees. However, ridge trees gave 3.6 kg per tree more. In 1993, two-year-old trees of Rode Boskoop on M.9 were jlanted in a third trial. The planting distance was 2.75 x 0.60 m and trees were either )lanted in a ridge or normally in the ground. Here, ridges were covered or not with nushroom compost. In the second year, ridge trees grew somewhat less than trees in he ground. After the 1995 season, ridge trees gave 8 m growth per tree totalled for he whole period and normally-planted trees 10 m. In production there was hardly any lifference (6 to 7 kg per tree in 1994 and 9 to 10 kg per tree in 1995). In both years \mid Thin was used as a thinner. In 1996, again trees flower well, "here are also experiments with trees planted further apart, namely with Elstar on M.9 >lanted at 3.00 x 1.00 m. Here, trees were planted in 'hills' instead of ridges. Again, a jood start was obtained with all trees and in the second year trees produced well and iad a moderate vigour. After four seasons there is still no reason why hill trees should lot continue to give good production. In this trial no bending of laterals was carried out, ind it seems possible to save bending-labour when trees are planted on the ground. n summary, it appears that by planting trees on the ground the problems of replanting ire diminished. Furthermore, it appears that labour can be saved in pruning and >ending. Requirements are such that ample water and nutrients should be provided and :hemical thinning must start early in the life of the trees. Concerning water, it should be tressed that sprinkler irrigation must be present. Trees in ridges are more prone to vater stress if no rain comes on time. It remains to be seen whether the good results »btained on the good soil in Zeewolde can be achieved elsewhere. In future research, ittention will paid to better tree uniformity and further improvement in the start of the rees. 43 A.R. 1995 Research Station for Fruit Growiru Evaluation of Top Fruit Cultivars Cultivar testing with apple H. Kemp and M.CA. van Dieren Cultivar testing in Wilhelminadorp In the spring of 1995, 92 apple cultivars were planted in the cultivar trials at Wilhelmi nadorp. A large number of these cultivars are scab-resistant. Many cultivars originatec from Rumania, United States, France, The Netherlands and the Czech Republic. Almos all cultivars were included in a parcel with, and in a parcel without, fungicide applicati on. Nearly all cultivars stood on the M.9 rootstock. In the winter 1995/1996, 31 cultivars were grubbed for different reasons (Table 33). Rejected cultivars are no necessarily inferior cultivars, because in a number of occasions cultivars/mutants/selec tions are grubbed as they are not better than the current assortment. Table 33. Data of the cultivars grubbed in winter 1995/'96, PFW Cultivar Origin Planted Characteristics eating others quality* 8S-27-43 Canada 1993 m sweet 8S-32-62 Canada 1993 m unattractive fruit Ahrina Germany 1994 m somewhat unattractive fruit Ambro TheNetherl. 1994 m small fruit (without fungicides) BFA 80/2-10 # Germany 1994 m some bitterpit, small, cracked, unattractive fruit BFA 80/2-29 * Germany 1994 mg some bitterpit, unattractive fruit BFA 81/19-24 * Germany 1994 m somewhat unattractive fruit BFA 81/19-47 * Germany 1994 m cracked, rotten fruits BFA 81/19-57 * Germany 1994 m unattractive fruit BFA 81/19-76 * Germany 1994 m somewhat small, unattractive fruit, bitterpit BFA 81/19-82 * Germany 1994 m somewhat mouldy core and rot, bitterpit BN 3/43 * Rumania 1995 pm some scab CPRO 81003- 49 The Netherl. 1991 mg small fruit, little scab and mildew CPRO 84001- 30 The Netherl. 1993 m mouldy core, unattractive fruit Delrouval France 1991 m soft scald E55/59 England 1993 mg somewhat mouldy core and rot FAW 2151 Switzerland 1994 m fruit skin spots Gris Braibant * Belgium 1994 mg cracked fruits H 1203 Germany 1993 mg somewhat acid 44 A.R. 1995 Research Station for Fruit Growing /lelodie * Czech Rep. 1994 m acid JY 66305-139 * USA 1995 pm » 1300 France 1995 mg selection of Gala, sweet, somewhat more colour than standard Gala 1302 France 1995 mg selection of Tenroy, sweet, somewhat more colour than standard Gala H-FL-GR 86/3 * Switzerland 1994 m unattractive, small, sweet fruit H-FL-RU 86/1 * Switzerland 1994 mg somewhat unattractive, small fruit H-FL-RU 86/3 * Switzerland 1994 mg small, rotten, cracked, unattractive fruit, bitterpit around stalk H-FL-RU 86/5 * Switzerland 1994 pm small, somewhat unattractive, sweet fruit H-GR 1/79 Switzerland 1994 m small, somewhat unattractive fruit A-2,209 Germany 1994 m rather fast break down i-A-3,129 Germany 1994 mg A-25,286 Germany 1994 mg attractive fruit res. Roulin Belgium 1994 m ed Devil England 1994 pm acid, bitterpit eleta * Germany 1994 m short fruit stalk ene * Germany 1992 m somewhat small, grey fruit etina * Germany 1992 pm somewhat small fruit, soft scald, break down PAB 918 New Zealand 1994 m small, insipid-sweet fruit, fruit tree canker, scald PAB 920 New Zealand 1994 m somewhat small, russeted, cracked, unattractive fruit pm= poor to moderate; m= moderate; m g; moderate to good. Cultivars followed y a * are (highly) scab-resistant. uring summer, the trees on the plot without fungicide application were checked for ie occurrence of scab and powdery mildew. At harvest, the fruits were screened for ie occurrence and level of scab infection. Part of the results is given in Table 34. i 1995, just as in 1994, almost no scab was found on the resistant cultivars. Only nth BN 3/43 and BN 26/245 was relatively much scab observed; with Ecolette (CPRO 8039-18) one fruit with a single spot was detected. As in 1994, in 1995 strikingly ss scab and mildew were found on CPRO 81003-49, a selection from Discovery x ames Grieve. However, the eating quality and fruit size of this early-ripening cultivar 'ere unsatisfactory (Table 33). Storability and shelf life were relatively good. CPRO 4015-17 had no scab in 1995, and only a very little mildew (Table 34). This rather w vigour selection from Elstar x Prima tasted rather good, but the fruit appearance 'as not optimum. Ahrista is a German, scab-resistant, autumn cultivar with a rather Dod taste and very low mildew susceptibility. 45 A.R. 1995 Research Station for Fruit Growini In winter 1995/1996, ten taste tests with resistant and non-resistant apple cultivar were carried out, and also one with six Cox's mutants. All tests were done at th' research station in Wilhelminadorp with about 30 employees as participants. The fruit of all cultivars were stored at 3 °C until two to four days before the test (only Otava Table 34. Rating for occurrence of scab (at harvest) and mildew (June) in 1995 PFW Cultivar Years without Fruit Leaf/shoot fungicides scab* mildew* non-resistant cultivars Braeburn 2 2 1 Cox's Orange Pippin 6 3 2 Discovery 6 2 1 Elise 6 3 0.5 Elstar 6 6 4 'Gala (Regal Prince) 5 — 2 Golden Delicious 6 7 1 Jonagold 3 - 5 Rode Boskoop S.H disease-resistant cultivars Ahrista 2 0 1 CPRO 78038-9 6 0 7 CPRO 84015-17 3 0 0.5 Delorina 4 0 3 Ecolette (CPRO 78039-18) 6 1 1 Enterprise (Co-op 30) 5 0 2 Fiorina 6 0 4 Gerlinde 2 0 2 Prima 6 0 0 Priscilla 6 0 2 SA 15/ 4 3 0 1 Topaz 1 0 — ) 0= none; 1= very little; 9= excessive occurrence. Not observed. was partly stored at ULO) and afterwards displayed at room temperature (at the sami time, the fruits of the Cox's mutants were also exposed to temperatures between 1( °C - 20 °C for almost a week). The results of the tests with scab-resistant appli cultivars until November 1995, have been published in the Dutch magazine Fruitteet 85(1995)50:16-18, together with a description of the interesting new cultivars. Th< results of the tests up to November with the non-resistant cultivars have been published in Fruitteelt 86(1996)3:16-17. In this article some cultivar descriptions are given, also Table 35 mentions the results of the tests after November 1995. The taste of Rene was disappointing as in November 1994. Otava tasted rather good 46 A.R. 1995 Research Station for Fruit Growing sut production, fruit size and appearance are not optimum. Several tasters mentioned joldRush and Co-op 36 as (too) hard, and Golden Delicious and Co-op 34 as (too) soft, )n 19 December. Co-op 37 was somewhat insipid. On 12 January 1996, Golden Delicious and Jonagold were described as too soft; Gala also was judged already (too) soft. Delblush was still crisp and juicy. Elise was between those two. In February, joldRush, a very late-ripening cultivar, was rated considerably better than in January. The assessment of FAW 7262 was disappointing. The taste test in February was fable 35. Taste tests with apple cultivars winter 1995/'96 PFW. "ultivar Taste score 18-12'95 19-12-'95 12-01-'9 6 02-02-'96 :o-op 34 # — 5.3 a ... :o-op 36 # ... 5.4 a ... 4.3 c :o-op 37 # — 5.5 a — 5.5 b :PRO 78038 -9 # 5.5 ab ... — 4.6 c Delblush ...... 6.4 a 6.5 a Delorina # 5.4 ab — ... Ecolette # 5.1 bc — ... Elise ... — 6.2 a :AW 7262 # — — — 4.2 c 3ala ...... 5.1 b Bolden Delicious 5.5ab 5.7 a 5.2 b 3oldRush # — 4.9 a ... 6.1 ab lonagold — — 4.8 b Dtava # 5.8 a ...... Rene # 4.5 c ...... ) 1 = very poor to 9 = excellent taste. Values in one column followed by the same etter(s) do not differ significantly (P= 0.05). f = Scab-resistant cultivar obviously too late for CPRO 78038-9 stored at 3°C. In :ebruary, Delblush was still firm and juicy. Delblush has a special flavour. n 1995, five colour mutants of Delcorf and standard Delcorf (Delbarestivale) were inder trial. The French mutant Dalili (Ambassy®) was attractively blushed, and had loticeably much more colour than the standard. Another French mutant, Monidel, had ilso a high percentage of blush and attractive fruits in 1995 (first year). Delcorf ïversdijk had rather much colour, but also rather many chimaeras. The mutants Delcorf Jicolaï and Celeste (Delcorf Schuhmann) were only slightly better than standard )elcorf. 47 A.R. 1995 Research Station for Fruit Growing Clone trials in Wilhelminadorp Cox's Orange Pippin The trial (069-Wi9102) with 21 clones, that was planted in the spring of 1991 (maidens on M.9) yielded well in 1995 for the fourth time. The production, vigour, fruit size, colour and russeting data have been published in Fruitteelt 86(1996)17:20-22. Also the data of the Queen-Cox-clone trials (069-Wi9205, 069-Wi9206 and 069-Wi9207) planted in the spring of 1992, have been included. The production of these trials was also good, in 1995. In a taste test on 10 November 1995 with T12, Cox's la Vera, Cox's Zwanenburg, Crimson Cox and the Queen-Cox-clones 13 and 91 no significant differences were found. Boskoop In the spring of 1995, a trial (069-9502) with 15 mutants of (Rode) Boskoop was planted. The trial was also planted in the regional experimental garden in Horst. The colour mutants Celica (Welbo), Bielaar and others and some spur types were included. Clone trials in regional experimental gardens Jonagold In the spring of 1992, a trial with 13 colour mutants was planted in the regiona experimental gardens in Horst, Numansdorp and Zeewolde. The trial (069-9201 comprises Wilmuta, Crowngold, Schneica B (Jonica B), King Jonagold 8765 T, Jonakap (Jonagold De Jager I), Decosta (Swillen, DC, Verbeek), Jonagored 9614 and Jonagorec HR 2458 (probably virus free), and Jonabel (Jonagold Van Gelder), Jonagold 2000, Novajo (Jonagold Veulemans), Jonaveld (Jonagold In 't Veld) and Jomured (Jonagold VandePoel) (probably virus infected). The trial in Numansdorp was grubbed in wintel 1994/1995, because this site has been closed, and the trial in Horst was grubbed ir winter 1995/1996, because of severe fruit tree canker infection and the economy o1 the Dutch fruit research. In 1995, the mutants Wilmuta, Novajo, Crowngold, Jonaveld, King, Jonagored, Schneica B and Decosta have been picked on five dates. All samples were tested foi the amount of blush, ground colour, fruit weight, firmness, eating quality and sugar anc acid contents, partly before and after storage. The first results of this large experimenl have been published in the Dutch magazine Fruitteelt 86(1996)26:20-21 by Roelofs. Elstar A trial with nine interesting new colour mutants of Elstar was planted in the experimen tal garden in Zeewolde in the spring of 1995. The first results with the bright and dark red mutants will be obtained in 1996. Boskoop See Clone trials in Wilhelminadorp. 48 A.R. 1995 Research Station for Fruit Growing îultivar testing with pear '. Kemp and M.C.A. van Dieren ultivar testing in Wilhelminadorp i the spring of 1995, 28 new cultivars were included in the test blocks. Nine cultivars re claimed to be barely susceptible to fire blight. All cultivars are tested in groups of 3n trees with a standard fungicide application programme and since the spring of 994, also in groups of five trees without such a programme. On this plot, the usceptibility to fungal diseases is tested. Nearly all cultivars stood on Quince MC with n interstem (Beurré Hardy, since 1994 Doyenné du Comice). With three of the 70 ultivars under test on the unsprayed plot, fruit scab was observed in 1995, the most eing on Saint Remy. In the spring of 1995, branches with scab spores were brought in Dincreas e the source of infection. In the spring of 1996, infected branches and leaves om several cultivars will be brought in again. l winter 1995/1996, two cultivars were rejected. In particular, the French cultivar automne, planted in spring 1990, was rejected for its somewhat grey, bumpy, nattractive fruit appearance. The production and storability were good; the taste was îther good, too. BP 9627, a selection planted in 1993, from the common Swedish/Nor wegian breeding programme, was rejected mainly for its bumpy, somewhat fatty, nattractive fruit. he trees of Dolacomi (Jowil®), planted in spring 1983, were replanted in the autumn of 994, and did not yield in 1995 because of being replanted, as well as the dry and warm summer. In winter 1995/1996, many flower buds could be observed. After a ood yield in 1995, the younger trees of Dolacomi (planted spring 1992) showed only 3w flower buds in winter 1995/1996. Through the NAKB, propagation wood has been able 36. Results of taste tests with pears, winter 1995/96 ultivar Score* 22-11-1995 12-02-1996 onference ... 5.9 ab elbuena 5.9 bc 5.2 bc elmoip ... 4.7 c olacomi (Jowil®) 6.4 b 6.2 a 'oyenné du Comice 7.0 a ircas 5.7 c erdi 6.2 bc 5.7 ab 1 = very poor; 9 = excellent taste. Values in one column followed by the same itter(s) do not differ significantly (P= 0,05). 49 A.R. 1995 Research Station for Fruit Growin available for the nurseries since summer 1995. Meanwhile, the NAKB has applied fc European Plant Variety Rights for Dolacomi (Jowil®). The unramified maidens of Verc on Quince MC with an interstem of Doyenné du Comice, planted in the spring of 1994 have shown (very) much ramification and vigour during the last two years. Althoug there was good flower bud formation in 1995, it is not advisable to plant unramifie Verdi trees. In winter 1995/1996, three taste tests with pears were carried out at the researc station in Wilhelminadorp. All fruits used in these tests were stored at 21 % 02 and °C up to about six days before testing, and were then exposed to 18-20 °C. In Febru£ ry, the fruits of Delmoip were exposed to room temperature two days earlier than th other cultivars to obtain sufficiently soft fruits. Thirty employees took part in the test with different cultivars (Table 36), and 20 in the test with large and small fruits c Delbuena (Table 37). Table 37. Taste test with large and small fruits from Delbuena trees with différer crops, 20 November 1995, PFW. Crop/fruit size Grading (mm) Score* Light/large 75-80-85-90 6.9 a Light/small 60-65-70 5.8 be Heavy/large 70-75-80-85 6.6 ab Heavy/small 60-65-70 5.7 c *) 1 = very poor; 9 = excellent taste. Values followed by the same letter(s) do no differ significantly (P= 0,05). Dolacomi, Delbuena (Peradel®) and Orcas were judged insipid by some of the tasters Verdi was said to be acid by some participants. In spite of the two days' longer ripenin' time of Delmoip (Delbarexquise d'Hiver®, Passadel®), the fruits were still described a partly unripe by several tasters. Therefore, the score was negatively affected. Delmoi ripens late and can be stored and kept very well. In February, Verdi was already not i an optimum condition. In 1995, for the second time a taste test was done with large and small fruits fror moderately and heavily cropping trees of Delbuena (Table 37). As in 1994, the larg fruits had a better taste than the small ones. Because of its low vigour and good flowe bud formation and fruit set, Delbuena has relatively many fruits and few leaves, an this will negatively affect its fruit size and taste. In 1996, Delbuena and Dolacomi wi be budded on the more vigorous rootstocks Quince MA and BA 29 to find out if th£ will positively affect the leaf/fruit-ratio. 50 A.R. 1995 Research Station for Fruit Growing lultivar testing with stone fruit 7. Kemp, H. Wustenberghs and M. Balmer "ultivar testing with plum in Wilhelminadorp •y. Kemp n 1995, four cultivars were planted: two from Sweden, one from England and one old ;ultivar from Belgium. These cultivars were also planted at the Fruitteeltcentrum of the C.U.L. in Rillaar (Belgium). Eight cultivars were rejected (Table 38). able 38. Data of plum cultivars refected in winter 1995/'96, PFW. ^ultivar Planted Kg/tree Fruit Taste Picking Remarks weight(g) period /66071 1992 0.5 43 fair 2nd week dark-blue August bloom ve 1988 13.2 63 rather 4th week dark-blue good August sweet Î.-Claude 1987 7.3 51 good mid- dark-blue îouffriau August bloom ^arpatin 1992 4.1 48 fair 1st week dark-blue, sweet August russeting and spider mite, late-flowering 'efferson 1992 0.9 50 good 1st week sweet, yellow September I 70-S-483 1992 0.3 58 fair 2nd week dark-blue August bloom Lilia 1992 0.2 39 fair 3rd week dark-blue August 'itestean 1994 0.9 52 moderate mid- late-flowering August iootstock: St. Julien A. Planting distance: 4.0 x 2.75 m. In 1990 and 1991, the iarvest was almost totally destroyed by severe spring frosts. "he Canadian selection V66071 was rejected because of insufficient taste and yield and trong vigour. Ive, from Sweden, has many pleasing characteristics, but has still isufficient improvement compared with the current assortment. Reine-Claude Souffriau lives good-tasting, attractive fruits, but the production per m3 is too low. The Rumani- n cultivars Carpatin and Pitestean were rejected for their prune shape and insufficient äste. Neither are they promising as a prune. Fl 70-S-483 (Firenze 90) from Italy, and 51 A.R. 1995 Research Station for Fruit Growinc Julia (Cacak 2747R) from Serbia, were grubbed because of the strong vigour anc insufficient production and taste. The old, American, yellow-fruited cultivar Jeffersoi tasted good, but can not enrich the current assortment; productivity is fair. Cultivar testing with sweet cherry in Ahrweiler (Germany) M. Balmer and H. Kemp In 1995, the German cultivar Nanni produced fruits weighing seven grams and showei little cracking. The fruit firmness was good for an early-ripening cultivar (second week) Merchant (second - third week) gave rather many (40%) cracked fruits. The fruit weigh of Merchant was good - over eight grams. Celeste and Giorgia (third - fourth week gave fruits of a good size and showed little cracking susceptibility. Giorgia is firm Celeste obviously less so. Magar (Garnet®) gave good-tasting fruits, but the size wa disappointing. Magar ripened in the fourth week. Noire de Meched (fourth - fifth week gave fruits of a good size with only a few cracked fruits. Taste and firmness wer good. In the same week, Nordwunder also ripened with similar fruit characteristics Sylvia (fifth week) was firm and rather large (almost eight grams). Karina (fifth week had good fruit size, too. The late-ripening cultivar (sixth - seventh week) Sweethear was sweet and not so acid. Sweetheart, Merchant, Giorgia and Celeste are nev cultivars that are recommended by "Ahrweiler" for trialling in practice. Cultivar testing with sweet cherry in Rillaar (Belgium) H. Wustenberghs and H. Kemp In 1995, there were at Rillaar about 100 sweet cherry cultivars under trial. Almost a cultivars stood on Damil (GM 61/1), with a few on Camil (GM 79) or Colt. In 1995 am 1996, a trial was planted with 20 new cultivars as a second screening. Four cultivars Schneiders Späte Knorpelkirsche, Kordia, Sylvia and Regina, which will function mor or less as standard cultivars, were also planted on the rootstocks Gisela 5 and Gl\ 61/1. All the other cultivars are only on Colt. The trial comprises the following cultivars: Lapins, Newstar, Starking Hardy Giant (viru free!), Summit, Somerset, Hartland, Maru (Ruby®), Sweetheart, Techlovan, 13S-5-22 Vernon, Karina, Fercer (Arcina®), Sumgita (Canada Giant), Sonnet (13S-39-51, ver large fruits, moderate production), 13S-49-24, 13S-35-43 (large fruits, firm am moderately susceptible to cracking), 18-15 (late-ripening, large fruits, rather productiv and moderately susceptible to cracking), Magar (Garnet®; not certain yet) and Veg (yellow fruits, large and firm). 52 A.R. 1995 Research Station for Fruit Growing rhe pollination of pome and stone fruit /. Kemp .rossings very year, crossings are made with apple, pear and/or plum cultivars to determine if ertain combinations of (new) cultivars can fertilize each other sufficiently. In 1995 at Vilhelminadorp, crossings were carried out by hand with apple, pear and plum (Table i9). Per crossing 100 (plum 80) flowers were used: five (with plum four) branches with en clusters with two flowers per cluster. Directly after pollination, the stigmas were overed with vaseline. »iscovery, little susceptible to scab, seemed to be a good pollinizer for the promising cab-resistant selection CPRO 78038-9. Golden Delicious gave only low fruit set on PRO 78038-9. Self-pollination with CPRO 78038-9 gave only much less fruit set in 995, which was in contrast with the rather good fruit set in 1994. The scab-resistant ultivar Enterprise seemed not to be self-fertile, but CPRO 78038-9 gave sufficient fruit 'able 39. Fruit set and number of good seeds/fruit of hand-made crossings at harvest, PFW 1995. ollinated cultivar Pollinizer % fruit set Good seeds/fruit ipple :PRO 78038-9 CPRO 78038-9 2 :PRO 78038-9 Discovery 18 :PRO 78038-9 Golden Delicious 7 lelblush Delblush 3 1.3 lelblush Golden Delicious 2 2.5 nterprise CPRO 78038-9 19 2.0 nterprise Enterprise 0 ear lolacomi (Jowil®) Dolacomi (Jowil®) 0 lolacomi (Jowil®) Gieser Wildeman 9 3.4 lolacomi (Jowil®) Triomphe de Vienne 9 1.6 iieser Wildeman Gieser Wildeman 0 Üeser Wildeman Verdi 0 lum xcalibur Jubileum 6 xcalibur Valor 3 Fruit set at harvest, except for the crossings on CPRO 78038-9. The data of the rossings on CPRO 78038-9 are from the end of June; the fruits were later lost. = Not determined. 53 A.R. 1995 Research Station for Fruit Growini set on Enterprise. The flowering periods of CPRO 78038-9, Discovery and Enterpris overlap sufficiently for a good mutual pollination. The interesting, French cultiva Delblush gave little fruit set after selfing and also pollination with Golden Delicious gav only few fruits. This is probably due to the relationship; Golden Delicious is the femal parent of Delblush. The flowering of these two cultivars is nearly simultaneous. The crossings on Gieser Wildeman failed, possibly because of the rather low temperatu re during the pollination period (about 14°C). Also the use of flowers mainly on one year-old twigs could have negatively affected the, also initially low, fruit set. Repetitioi seems significant. The flowering of Dolacomi (Jowil®), Gieser Wildeman and Triomphe de Vienne is sufficiently simultaneous for a good mutual pollination. The flowerini periods of Gieser Wildeman and Verdi overlap sufficiently, too. The low fruit set of botl crossings on the interesting, English plum cultivar Excalibur is probably partly due to thi rather low temperature during the pollination period (about 14°C). Repetition is necessa ry. The flowering periods of these three cultivars have rather a good overlap, althougl the first flowers of the early-flowering Valor will not be pollinated every year. Small Fruit Strawberry cultivar trials A.J.P. van de Waart, J. Dijkstra, A.A. van Oosten Cultivars in the open National cultivar trial As part of a national cultivar trial, in Wilhelminadorp Elsanta was compared to th< Dutch selections Lambada, CPRO 9302, CPRO 9402, CPRO 9405, CPRO 9407 and th< Swiss cultivar Thuriga. Also, in this trial different methods of raising Elsanta am Lambada plants were included. Normal planting was compared with cuttings and lightl\ rooted plants, that were put into trays at the end of July, followed by planting at th< end of August. Besides, Lambada was planted at double density in order to increase it! production per m2. The production level of all cultivars was similar to Elsanta. Lambada planted at double density gave a higher production than Elsanta. Cuttings o Elsanta and Lambada did not lead to an increased production. However, with thi: method less Verticillium was found. Thuriga is the only cultivar so far discarded. Thi: cultivar did give nice large dark red berries, but firmness and taste left a lot to b< desired. For a short cultivar description of the CPRO numbers, see the Annual Repor 1994, page 78. Everbearing cultivars National cultivar trial In Wilhelminadorp and Breda, again some new everbearers were compared in the oper 54 A.R. 1995 Research Station for Fruit Growing he plants were planted half of April, after they had been advanced for some weeks in greenhouse or tunnel. The harvest in Breda continued until the end of September, and Wilhelminadorp until the end of October. able 40 shows that Evita, as in the preceding years, was the most productive cultivar. ontrary to other years, this year Evita did produce many runners. he main characteristics of the cultivars Evita, Rapella and CPRO 1036 have been ascribed in the Annual Report 1994, page 80. able 40. Results of a trial with everbearing strawberries, Wilhelminadorp 1995 ultivar Kg/m2 Mean fruit weight (g) Number inner quality 1 quality 1 per plant apella 1.4 13 3 elva 1.0 18 14 vita 2.2 15 10 PRO 1036 1.0 13 28 ango 1.1 13 3 arsival 0.6 11 17 lara des Bois 0.8 12 13 unset 1.9 19 10 n the other cultivars the following information can be given. elva: solid large fruits but with a very moderate taste. arsival: solid small flat to long-conical fruits with a folded back calyx and a good to sry good taste. laria des Bois: solid, (too) small, conical fruits with an extremely folded back calyx. he taste was sometimes good but often had a too strong wild-strawberry flavour. ango: large, solid fruits, often striated and irregularly formed with a very moderate iste. unset: regular, very large, well coloured fruits, very much resembling Selva, but with a 3ry moderate taste. As in 1994, very susceptible for mildew. he results of Breda were in agreement with those obtained in Wilhelminadorp. ther strawberry trials he other cultivar and cultural trials with strawberry have all been realized in the xperimental garden Noord-Brabant in Breda and have been described in the Annual eport 1995 of this site. 55 A.R. 1995 Research Station for Fruit Growin Cultivar trials of bush and cane fruits A.J.P. van de Waart, A.A. van Oosten, and W.A.G.M. Jansen. Red and white currant First evaluation of new cultivars in the open. In 1993, a trial was started for a first evaluation of eight (new) red and white currar cultivars; Vitan, Rubigo, Losan, Maraton, Heros, Herosta, Mulka and Redwing. In 1994 Präkanda and Traubenwunder were added to this collection and in 1995: Cogagne Hron, Redpoll, Jobes, Redwing, Fertöd and Mivana. In 1995, Losan and Vitan drew the attention because of their rather early ripeninç Besides, Losan had good fruit quality. Rubigo had nice strings but small berries Maraton had suffered badly from mildew, and the same was true for a Redwing an Redpoll. Präkanda and Traubenwunder combined nice long strings with large berries Both cultivars ripened rather late. Heros and Herosta could not be evaluated properl because of cultivar mixing. For this reason further evaluation of these cultivars wa finished. Test new seedlings In 1994, evaluation of red and white currant seedlings began, originating from a privat breeder. Cultivar trial In 1993, a cultivar trial was started with 16 red, white and pink currant cultivars. Th experimental fields are situated in Geldermalsen and Wilhelminadorp. On both location: three replications of 15 plants of each cultivar were planted under rain covers. Th flowering and harvest data of 1 995 are given in Table 41. The following details can be given about the cultivars: Berry colouring of Rosa Sport did not proceed well under the rain covers. It is not cle; whether this is caused by the plastic (polyethylene PE) cover. Rotet didn't satisfy und* rain covers; growth was disappointing, berries remained too small and production WE low. Rolan, on the other hand, performed remarkably well under the rain covers. Th light-coloured and acid tasting berries need to be picked late in order to develop goo colour and taste. This is possible under rain covers without the risk of cracking induce by rain. Rondom J, again, gave a very moderate production due to lack of chillinc August proved to be a very late ripening cultivar. In spile of the remarkably ear flowering under the rain covers. In 1995, the first flower was seen on 3 April. For tr early flowering and early ripening cultivar Jonkheer van Tets, first flowers opened on April. 56 A,.R. 1995 Research Station for Fruit Growing rable 41. Flowering and harvest data 1995 of a cultivar trial of red currants in Wilhelminadorp ^ultivar Harvest 1st Kg/100 m2 100 Number date bloom l+ ll quality berry- berries/ weight(g) truss i.v.Tets 3-7 5-4 163 86 6,4 lunifer 3-7 8-3 289 76 9,5 tosa Sport 18-7 3-4 118 79 11,3 )etvan* 18-7 13-4 95 81 12,1 totet 21-7 7-4 99 82 10,2 tolan 25-7 16-4 184 111 10,4 stanza 25-7 15-4 185 64 10,9 ^assa 26-7 7-4 179 99 13,8 tovada 7-8 14-4 214 82 18,5 "atran* 7-8 16-4 72 100 13,5 Rondom H 7-8 18-4 152 90 17,1 toodneus 15-8 24-4 229 72 19,5 tondom J 21-8 1-5 39 82 15,0 augustus 21-8 3-4 233 63 27,3 'rimus 26-7 3-4 173 64 15,0 ïlanka 27-7 28-4 169 79 19,2 • Detvan and Tatran have been planted one year later •valuation of red currant cultivars their suitability on mechanical harvesting. n 1995, in two commercial orchards in Heinkenszand, practical trials were planted for a :ultivar evaluation on their suitability for mechanical harvesting. The best cultivars are 'rince Albert, Rotet, Rovada, Stanza, Rode Rebel and Rondom H. :irst evaluation of new cultivars in a plastic tunnel i 1994, a trial was started with 11 red and white currant cultivars in a plastic tunnel, ïamely with Albatros, Zitavia, Werdavia, Junifer, Red Lake, Rosa Sport, Fay's Prolific, axton Perfection, Herosta, Jonkheer van Tets, and Laxton no.1. In 1995, Vitan was dded. At the end of the season it was decided, for economical reasons, not to ontinue the evaluation of the white currant cultivars, Albatros, Zitavia and Werdavia. here is only little interest in practice for white currants. Evaluation of the red currant ultivar Herosta was ended evalution of, because of its insufficient berry quality. In 996, the very early ripening selection Darthuyzen and the cultivars Detvan and Losan vere added to the trial. 'lones and virus-free Rondom plants i 1993, 18 clones of PFW and three virus-free T-numbers from the NAK-B (Inspection 57 A.R. 1995 Research Station for Fruit Growini Service for Floriculture and Arboriculture) were planted out for comparison. In 199! many differences between the Rondom clones were observed. There were clones witl short, or rather long or with dense strings. Others, however, had thin strings. Th berries varied from small to large. Three clones were considered to be promising. On clone was affected by the 'Rondom Disease'. Diseased plants are characterized b anomalous, nettle-like and large-sized leaves. This is coupled with the occurrence o small berries, strong running-off, infertility and bare branches. In general, most clone had high production and good berry quality. This was also true for the virus-free T numbers. The 'Rondom Disease' was not observed in these T-numbers. Evaluation of cultivars for their susceptibility to diseases and pests In 1995, 45 cultivars and selections were evaluated for symptoms of Red currant bliste aphid (Cryptomyzus ribis L) and mildew. Differences between cultivars were observée but it is still too early to come to conclusions. Black currant First evaluation of new cultivars and selections In 1991, a trial was started in which new cultivars and selections were evaluated fc the first time. In 1995, 38 cultivars were included in this trial. Harvest data of 2 cultivars and selections were registered. The other ones did not yet bear fruit. The mos important characteristics are given in Table 42 (cultivars without or with little mildew and Table 43 (mildew susceptible cultivars). For economical reasons, the trial wa concluded after the harvest of 1995. Evaluation of cultivars for their susceptibility to diseases and pests In 1994, 46 cultivars were planted for evaluation of their susceptibility to mildew, lee gall midge, and aphids. Till now, no conclusions can be drawn concerning leaf ge midge and aphids. The susceptibility to mildew corresponds to above described trial. Gooseberry First evaluation of new cultivars and selections In the 1989 trial, in 1995 only visual observations were carried out. This did not rend* new insights. For a detailed description of the cultivars, see the Annual Report 1994, [ 84-85. The trial is now finished. The trial started in the winter of 1994/1995 has bee adjusted after the season 1995. The cultivars Greenfinch, Remarka, Captivato Hinnomäkii (yellow) and Hinnomäkii (red) have been grubbed. The following cultivai were added to the trial: Resistenta, Cireus, Kozachoh, and K1-15-17. 58 A.R. 1995 Research Station for Fruit Growing Table 42. Characteristics of black currant cultivars without or with little mildew Cultivars Flowe- Harvest Growth Vigour Pro- Berry Truss Leaf ring time habit due- size length a bs c is period tion sion 1 2 3 4 5 6 7 8 Andega 5 4 4 7 8 4 8 8 3en Alder 9 9 5 3 5 6 3 5 3en Connan 5 6 7 5 8 7 1 2 3en Loyal 6 6 3 8 9 7 9 2 3en Tirran 10 10 5 4 5 6 4 3 3en Tron 2 1 10 8 8 8 2 2 Deres 1 1 2 9 9 8 9 3 E.C.M. 4 5 2 5 9 9 8 1 Haakon 8 5 7 5 4 8 2 2 1:1= early, 10 = late 4: 1 = weak, 10 = strong 6: 1 = small, 10 = large 1: 1 = early, 10 = late 5: 1 = low, 10 = high 7: 1 = short, 10 = long 3: 1 = drooping, 10 = upright 8: 1 = little, 10 = much Table 43. Characteristics of mildew susceptible black currant cultivars ;ulti- Mildew Flowe Harvest Growth Vigour Pro Berry Truss Leaf ring time habit duc size length abs period tion te cis sion 1 2 3 4 5 6 7 8 9 .omond 8 3 3 5 7 8 8 7 3 3.Nevis 8 4 3 4 6 7 5 6 3 Dmeta 5 7 6 5 7 7 5 8 6 3hoenix 9 8 7 6 9 9 8 8 6 Silgo 9 5 4 8 8 8 7 7 6 Trench 8 4 4 7 5 ? 2 5 9 Tsema 9 3 3 3 9 9 6 8 8 5oper- lik 9 5 6 9 4 ? 3 5 6 1:1= little, 10 = much 5: 1 = weak, 10 = strong 9: 1 = little, 10 = 1: 1 = early, 10 = late 6: 1 = low, 10 = = high much 5: 1 = early, 10 = late 7: 1 = small, 10 = large V. 1 = drooping. 10 = u pright 8: 1 = short, 10 = long 59 A.R. 1995 Research Station for Fruit Growin« Evaluation of cultivars for their susceptibility to diseases and pests In the spring of 1995, 23 gooseberry cultivars were planted for evaluation of mildev susceptibility. Although differences between cultivars were found, it is still too early t< draw conclusions. However, the trial was concluded at the end of 1995 for reasons o er... in the budget. From now on, this type of work will be part of the first evaluation o new cultivars and selections. Blackberry First evaluation of new cultivars and selections In the spring of 1993, eight cultivars were planted in the open under rain covers. O these cultivars, Silvan and Kotata were grubbed after the harvest of 1995. Kotata wa no improvement of silvan; it ripens about four days later, production is lower, and fruit are smaller, yhe fruits are more solid, less fragile and have a deeper black colour. In the spring of 1994, six cultivars were added to the collection. Of these, Orego Thornless Evergreen and Bödermö has been removed because it bears a logan-typ berry and this does not match with the other cultivars. In the spring of 1995, th following thornless cultivars and selections have been added: Douglas, G6, Navaho two origins of Chester Thornless, and Adrienne. No differences were found betweei the two origins of Chester Thornless. All Plants of Adrienne died. Hopefully, in th spring of 1996 new plants can be planted out. Evaluation of cultivars for their susceptibility to diseases and pests In the spring of 1994 and 1995, 19 cultivars have been planted out. In 1995, th cultivars were evaluated for infestation by cicadas. In the cultivars planted out in 1994 a heavy infestation was found; in the cultivars planted out in 1995, little infestatioi was found. No cultivar differences were detected. Raspberry First evaluation of new cultivars and selections. The trial with Granat, one of the first four new cultivars, planted out in the spring o 1993, has been discontinued. As in 1994, this cultivar suffered a great deal from roo and stem dieback. Fruit quality was moderate; fruits were small, dark-coloured, rathe soft and of moderate taste. The other three cultivars gave a result corresponding to th result of 1994. (See Annual Report of 1994, p. 88). The first, provisional results ar given for the ten new cultivars and selections, planted out in the spring of 1994. 71/11/153. A moderate number of thorns. Healthy growth. Early ripening. (Too) small solid, rather dark-coloured, well tasting fruits. Productive. Algonquin. Few thorns. Moderate to good vigour. Dark-coloured, shining, small leaves Healthy. Small, round, shining fruits. Productive. 60 A.R. 1995 Research Station for Fruit Growing ieskid. Spiny. Good vigour. Healthy. Rather round, rather small, somewhat dull fruit. /loderate taste. Productive. lida. Has only a few thorns. Rather healthy. Long, thin stems. Nice, cone-shaped, arge, bright-red, well tasting, rather solid fruits. Rather early ripening. Productive. iaia. Spiny, Good vigour. Healthy. Very long fruit stems. Very large, irregular, dark- oloured, purple-red, fruits, with a moderate taste. Late ripening. Productive. ulia. Large number of thorns. Good vigour. Healthy. Solid, regular, pointed, somewhat ull fruit, with a moderate taste. Productive. 'echt's Gigant. Spiny. Healthy but moderate vigour. Makes vigorous, but not many oung shoots. Short fruit stem. Solid, round, medium sized, rather dark-coloured, good asting fruits. roma. High number of thorns. Healthy growth. Granular, soft, rather dark-coloured, ather small, good tasting fruits. Productive. lesa. Few thorns. Short fruit stem. Moderate leaf condition. Rather large, round, rather oft fruits with a moderate taste. Moderately productive. ulameen. Few thorns. Susceptible to root diseases. Very large, pointed, bright-red, ood tasting, solid, late ripening fruits. Rather productive. i the spring of 1995, ten new cultivars and selections were added to the collection: :8/1605-1, Wavi, Meco, 87-15-98, Rubacca, Glen Ample, Glen Magna, Glen Rosa, îlen Shee, and Glen Garry. 'ultivar trial under rain covers i the spring of 1993, a cultivar trial was started in the open under rain covers with ten ultivars in Wilhelminadorp and Geldermalsen. able 44. Harvest data 1994/1995 of a cultivar trial with raspberries ultivar Kg/100 m2 Average Harvest date qual. I+ II fruit weight.(g) 5% 95% versdijk 92 3.9 1-7 21-7 iutrago 110 4.4 2-7 22-7 chönemann 105 3.9 2-7 23-7 leeker 120 3.4 3-7 22-7 1arwé 97 4.6 3-7 24-7 umiloba 121 4.4 3-7 23-7 l 1994, four cultivars were removed because of a heavy attack by Phytophtora-root isease, viz. Glen Moy, Glen Clova, Gradina, and Comox. In 1995, the trial was ontinued with six medium to late ripening cultivars. The results are given in Table 44. if the cultivars, following information can be given. versdijk. Good quality and good taste. leeker. Strong and healthy vigour. Fruits solid and good taste. Appearsan excellent, ite ripening cultivar with, unfortunately, fruits of a somewhat too small size. 61 A.R. 1995 Research Station for Fruit Growinç Marwé. Healthy grower. Nice and solid fruits. Rumiloba. Nice, round, light-coloured, moderately solid, well tasting fruits. Rutrago. Granular, irregular, rather soft fruits. Schönemann. Mildew on the fruits. After the harvest of 1995, the trial was concluded. Origins of Schönemann In the spring of 1995, three origins of Schönemann have been planted for comparisor with the standard type. These were Kraege, Penkhues and Meyer. No results can as ye been given. Cultivar trial with cold-stored plants In a plastic tunnel without heating, 16 cultivars were evaluated for a late culture wit! cold-stored plants. The plants were taken out of the cold-storage room (-2°C) on Jun« 1st 1995, potted and raised in a plastic tunnel. Tulameen satisfied very well with 182 kg 1st and 2nd quality per 100 m2; 92% firsl quality and an average fruit weight of 3.9 g. Once again, Eversdijk late turned out to bi susceptible to stem dieback. Evaluation of cultivars for their susceptibility to diseases and pests In the spring of 1994 and 1995, a total of 60 cultivars have been planted. In 1995, a cultivars were evaluated especially for infection by Phytophtora-root disease. Cultivar that did not, or hardly suffer, are: Glen Lyon, Dinkum, Ruby, Rumiloba, Rutrago Marwé, Eversdijk, Glen Coe, Augusta, Elida, Gaia, Julia, Redsetter, Algonquin, Nootka Rusilva, Himbostar, Multiraspa and Pecht's gigant. However, it is still too early for fine conclusions. Cultivar trial with a forced culture in a plastic tunnel In 1995, 21 cultivars and selections were under test. The plants stood in 7.2 I contai ners. The following information can be given on the cultivars. 71/11/153. Rather productive, fairly small, pointed, rather dark-coloured, solid, we tasting fruits. Healthy growth. Algonquin. Rather early ripening. Productive. Small, shining, rather dark-coloured, we tasting fruits. Healthy. Balder. Productive. Small, solid, well tasting fruits. Elida. Productive. Large, pointed, bright-red, well tasting fruits. Fruits ripened rathe late. Eversdijk. Rather productive. Large, rather dark-coloured, well tasting fruits. Gaia. Very late ripening. Productive. Large, rather dark-coloured, shining, rather solic granular, but fairly well tasting fruits. Glen Ample. Productive. Large, round, somewhat granular, rather solid, well tastin 62 A.R. 1995 Research Station for Fruit Growing •uits. !len Garry. Rather productive. Large, somewhat pointed, somewhat dull-red fruits of loderate taste. Fruit with remarkably long sepals. Leaves strongly dentate. ilen Moy. The earliest ripening and also one of the most productive cultivars. Unfortu- ately, in practice, these good results can not easily be achieved because of damage aused by root diseases. In the trial root diseases hardly occurred. ilen Lyon. Rather early ripening. Productive. Round, solid, bright-red, rather acid asting fruits. ilen Prosen. Productive. Rather large fruits. This cultivar satisfied very well in this trial. ilen Rosa. Rather early ripening. Productive. Small, round, rather dark-coloured, well asting fruits. ilen Shee. Moderately productive, because of stem dieback. Fruits large, round, of )ose structure, of rather light-coloured and well tasting. ilen Magne. Rather productive. Large, somewhat granular, rather soft, purple red fruits. ulia. Very productive. Rather large, pointed, solid dull-red fruits of moderate taste. flarwé. Productive. Very large fruits, somewhat difficult to pick. fleco. Moderately productive. Small, round, solid, well tasting fruits. lesa. Early ripening, moderately productive, with small round fruits. lumiloba. Productive. Large, somewhat granular, light-coloured fruits. "ulameen. Productive. Large, pointed, solid, nicely coloured, well tasting fruits. Healthy rower. or economical reasons, this trial will not be continued. •ultivar trial with autumn-fruiting raspberries in a plastic tunnel a new-heated tunnel, 18 cultivars are being compared. The plants were potted in the arly spring of 1995 in 7 I containers. Harvest data are given in Table 45. he following details can be given for the new cultivars. ,ll Gold. Good vigour. Spiny stems. Fruits round, amber coloured and well tasting. eems to have little susceptibility to stem diseases. It was the best yellow autumn- uiting raspberry. utumn Britten. Vigours. Stems highly spined. Fruits large, pointed, somewhat dull and ather acid tasting. utumn Cascade. Weak grower. Thornless stems. Very susceptible to mildew on the uits; almost all fruits were infected. Moreover, this cultivar seems to be susceptible to tern diseases. Therefore, Autumn Cascade is discarded. inkum. Moderate vigour. Stems densely spined. Again, this cultivar proved less atisfactory than Autumn Bliss. Production was lower, fruits were smaller, and ripening fas later. Also appears susceptible to stem diseases. Dinkum discarded. avourite. Fast grower. Stems highly spined. Fruits large, soft, and granular. Seems to ave a low susceptibility to stem diseases. Favourite is descarded. alante. Very vigorous growth. Stems spiny. Fruits rather large, somewhat round, and ather fragile. Seems to have little susceptibility to stem diseases. oan Squire. Moderate vigour. Stems thornless. Fruits rather small, somewhat round, icely coloured and rather solid. Seems to be susceptible to stem diseases. 63 A.R. 1995 Research Station for Fruit Growini Table 45. Harvest data of a cultivar trial with autumn-fruiting raspberries in plastic tunnel Kg/ Kg/ % Average fruit Harvest date 100m2 100m2 qual. weight (g) 5% 50% 95% Autumn Bliss 129 177 73 3.8 21-7 14-8 22-09 All Gold 138 180 77 4.0 22-7 14-8 29-09 Autumn Britten 164 212 77 4.6 22-7 19-8 4-10 Polana 82 124 66 3.5 27-7 19-8 30-09 Joan Squire 139 198 70 3.6 27-7 24-8 4-10 Dinkum 128 165 78 2.8 30-7 27-8 8-10 Zefa Herbsternte 109 172 63 5.3 31-7 22-8 4-10 Heritage 128 170 75 3.1 1-8 19-8 5-10 Ruby 91 133 68 3.8 2-8 23-8 3-10 Autumn Cascade 4 451) 91' 4.0 2-8 26-8 6-10 Medway Yellow 113 173 64 3.8 6-8 27-8 3-10 Kiwi Gold 147 181 81 2.8 7-8 25-8 28-09 Fall Gold 99 121 82 2.9 8-8 29-8 30-09 Terri Louise 174 258 67 5.2 9-8 29-8 27-09 Princesse 131 176 74 3.6 6-8 26-8 26-09 Favourite 108 178 62 4.6 14-8 8-9 5-10 Galante 154 204 76 4.7 19-8 17-9 12-10 Rossana 40 47 85 3.9 22-8 5-10 18-10 1) Most fruits were infected by mildew Kiwi Gold. Moderate to strong vigour. Stems highly spined. Fruits round, small, solid and well tasting. Seems to have a moderate susceptibility to stem diseases, but Kivv Gold is discarded. Medway Yellow. Moderate vigour. Stems thornless. Fruits pointed, yellow coloured with a moderate acid taste. Seems to be susceptible to stem diseases. Cultivars i: discarded. Polana. Moderate vigour. Stems spined. Fruits rather small, bright-red, with a gooi taste. Seems to have little susceptibility to stem diseases. The production was lowe than that of Autumn Bliss, and the fruit size was smaller. Cultivar is discarded. Princesse. Rather vigorous growth. Stems spined. Fruits rather soft, somewhat granula and well tasting. Seems to have little susceptibility to stem diseases. Cultivar i: discarded. Rossana. Good vigour. Stems highly spined. Late ripening. Production rather low Fruits rather light-coloured but very well tasting. Seems to have little susceptibility t< stem diseases. Ruby. Moderate vigour. Stems highly spined. Berries solid and bright-red, but granula and of moderate taste. Ruby seems to be very susceptible to stem diseases. Cultivar i: discarded. Terri Louise. Vigorous growth. Stems highly spined. Makes few basal shoots. Fruit large, pointed, rather fragile with a moderate taste and little flavour. Susceptible t( 64 A.R. 1995 Research Station for Fruit Growing lildew on the fruits. Little susceptibility to stem diseases. 'ultivar trial with autumn-fruiting raspberries in a continued crop in a plastic tunnel line autumn-fruiting raspberry cultivars were evaluated in a non-heated tunnel in a ontinued crop. The plants had been potted in the early spring of 1994 in 7 I contai- ers. In the autumn of 1994, first fruits were harvested. The producing part of the stem /as cut off after the harvest. In the spring of 1995, fruits were harvested from the »wer part of the perennial stem, being the part that had not been bearing fruits in 994. fter the harvest in the summer of 1995, the perennial stem was cut off completely. he young stem that grew from the base in the spring of 1995, produced fruits in the utumn of 1995. The harvest data of autumn 1994 are given in Table 46; those of Dring 1995 in Table 47 and those of autumn 1995 in Table 48. able 46 shows that Galante satisfied well. Production was high with a high percentage f first quality. Fruit size was very good too. Ripening was late. avourite satisfied too, but the percentage of first quality was lower. Fruits of this ultivar are granular and loose. olana performed very well too, but with smaller fruits than Autumn Bliss. Ruby, Luilin nd Princesse gave a good production, but fruits were rather loose, causing a low ercentage first quality. able 47 shows that Galante was also very satisfactory in the continued crop and that stood head and shoulders above all other cultivars. Remarkable is the early ripening of lis cultivar. All cultivars gave smaller fruits in the continued crop in spring 1995 than the autumn crop of 1994. able 48 shows that a number of cultivars in the continued crop produced less than in ie year before. All cultivars had smaller fruits. prudent conclusion could be that in a continued crop in which berries are harvested able 46. Harvest data of a cultivar trial with a continued crop of autumn-fruiting raspberries in the autumn of 1994 in a plastic tunnel Kg/ Kg/ % Average Harvest date 100m2 100m2 qual. fruit quai. qual. 1 weight I+ II I (g) 5% 50% 95% utumn Bliss 112 137 82 4.7 12-8 14-09 15-11 Diana 151 195 78 4.3 13-8 12-09 9-11 inkum 102 132 77 4.2 13-8 14-09 16-11 jby 136 188 72 4.9 19-8 21-09 7-11 3fa Herbsternte 115 141 81 5.7 21-8 24-09 20-11 jilin 65 95 69 5.3 26-8 16-10 26-11 incesse 127 186 68 4.3 3-9 8-10 19-11 îvourite 115 193 59 5.6 3-9 16-10 18-11 alante 172 193 89 6.8 8-9 16-10 16-11 65 A.R. 1995 Research Station for Fruit Growin from the same plants in the spring and in the autumn production and fruit size ma suffer. Especially, strongly growing cultivars qualify for such a continued croj Moderately vigorous cultivars like, Polana and Zefa Herbsternte, seem to be less fit fc a continued crop, because in spring the producing part of the stem is too short. Table 47. Harvest data of a cultivar trial with a continued crop of autumn-fruitin raspberries in the spring of 1995 in a plastic tunnel Kg/ Kg/ % Average Harvest date 100m2 100m2 fruit qual. qual. qual. weight. I I + II 1 (g) 5% 50% 95% Galante 169 188 90 4.1 20-5 11-6 3-7 Dinkum 75 95 79 3.3 22-5 4-6 28-6 Autumn Bliss 72 85 85 3.6 23-5 13-6 1-7 Luilin 25 32 77 3.6 25-5 12-6 3-7 Zefa Herbsternte 24 38 67 3.2 27-5 12-6 27-6 Favourite 72 97 74 3.8 27-5 14-6 1-7 Ruby 37 44 84 3.7 27-5 17-6 3-7 Polana 37 46 81 3.3 29-5 13-6 1-7 Princesse 72 80 90 3.5 31-5 19-6 2-7 Table 48. Harvest data of a cultivar trial with a continued crop of autumn-fruitin raspberries in autumn of 1995 in a plastic tunnel Kg/ Kg/ % Average Harvest date 100m2 100m2 fruit quality quality quality weight I l+ ll I (g) 5% 50% 95% Dinkum 110 157 69 3.4 30-7 4-9 9-1C Favourite 46 102 44 5.0 30-7 13-9 14-1C Zefa Herbsternte 36 67 54 5.1 6-8 9-9 13-1C Polana 146 192 76 3.5 6-8 10-9 5-1C Galante 122 165 74 5.3 6-8 17-9 13-1C Autumn Bliss 132 167 79 4.0 8-8 8-9 6-1C Princesse 133 175 75 3.9 8-8 17-9 11-K Luilin 62 90 68 4.4 9-8 13-9 13-1C Ruby 92 126 73 4.5 10-8 9-9 13-1C Blueberry W.A.G.M. Jansen In the spring of 1990, two-year-old bushes of various cultivars were planted, most < 66 A.R. 1995 Research Station for Fruit Growing lern originated in the United States. The cultivars Duke, Bluechip, Flordablue, Sunshi- eblue, Spartan, Collins, Pioneer, Bluecrop, no. 131, Nelson, no. 139 (= 'Chandler') nd Elliott were included in the trial and were evaluated till 1996. For Duke, Bluechip, lordablue, and Sunshineblue 'in vitro' material was used. uke, Bluechip and Flordablue consistently gave a lower production compared with ther cultivars (Table 49). Possibly, this is due to differences in the quality of the (anting material at the start of the trial. Classification of the cultivars according to the harvest period arly Duke, Flordablue, Spartan, Collins arly to mid-season Pioneer, Bluechip lid-season Bluecrop, 131, Nelson lid-season to late No. 139 ate to very late Sunshineblue ery late Elliott able 49. Production data of the blueberry trial of 1990 ultivar Production in kg/bush 1991 1992 1993 1994 1995 total uke 0.32 0.71 2.06 1.05 0.64 4.78 iuechip 0.12 0.26 1.30 0.86 0.43 2.96 ordablue 0.01 0.18 0.75 0.02 0.51 1.47 unshineblue 1.29 2.20 1.74 0.28 0.97 6.48 partan 0.61 2.42 3.51 1.27 0.47 8.28 ollins 0.46 0.64 2.51 1.21 0.61 5.43 oneer 0.75 0.94 2.45 1.16 0.58 5.87 uecrop 1.13 1.47 2.72 1.40 1.20 7.93 r. 131 1.24 1.42 3.64 1.49 1.57 9.35 elson 0.37 1.55 1.47 1.46 0.91 5.75 r. 139 1.51 1.31 3.99 1.70 1.40 9.91 liott 1.54 2.08 2.97 1.48 0.60 8.66 escription cultivars uke (Ivanhoe x Earlyblue) x (E-30 x E-11) (United States) oderate to good vigour. Fruits medium sized with a somewhat dark-blue colour, sening rather uniformly. Good taste. The petals remain stuck until the harvest. uechip (Croatan x US 11-93) (United States) oderate vigour. Compact, bushy and rather wide growth habit. Berries fairly large, ark-blue, and firm. Good taste. A high production seems possible but difficult to :hieve. More experience is required. 67 A.R. 1995 Research Station for Fruit Growirx Flordablue (Florida 63-20 x Florida 63-12) (United States) Reasonable vigour and productivity. Berries large and not very light-blue. Tast somewhat neutral insipid, but not bad. Sunshineblue (United States) Weak to moderate vigour. Bushy and compact habit. Bushes low and very productive Light-blue, uniform berries of medium size. Good taste with a somewhat special flavoui leaves remain during the winter. Spartan (United States) Moderate vigour. Upright habit. Good productivity. Large, light-blue, mealy berries wit a poor taste. Collins (Stanley x Weymouth) (United States) Moderate vigour and productivity. Upright habit. Berries large, light-blue, somewha more flattened than those of Earliblue and also ripening a few days later. Pioneer Vigorous grower with a bushy and compact habit. Bluecrop (Jersey x Pioneer) x (Stanley x June) (United States) Vigourous grower with upright habit. Young fruiting branchs may droop and therefor pruning must be directed towards the presence of a sufficient number strong branche in the bush. Productive good. Berries large, solid, with a slightly acid taste and a ligh colour. The bushes seem winter hardy. No. 131 Poor vigour during the first years (the plants came directly from the United States) Therefore, production moderate. Growth and production improved during later years Upright habit. Berries very large and less acid than those of Bluecrop. Will not b released and therefore not longer been evaluated. Nelson (United States) Rather vigourous and productive. Ripens in a relatively short period. Large, light-blu berries of good quality with a slightly acid taste. No. 139 (Chandler) Vigourous and productive cultivar of upright habit. Berries extremely large. Elliott (Burlington x (Dixi x (Jersey x Pioneer)) (United States) Vigorous, very bushy, upright habit. Good productivity. Berries medium sized, light-blu with good taste. Depending on the weather the harvest period can be long. Cultivar orientation In the spring of 1991, two-year-old bushes of various cultivars, most ly from Australie were planted for a first evaluation. The cultivars Cape Fear, Blueridge, '0 Nea 68 A.R. 1995 Research Station for Fruit Growing harpblue, Avonblue, Denise Blue, Blue Rose, Caroline Blue, and Brigitta Blue were bserved till 1996. Denise Blue, Blue Rose, and Caroline Blue gave a reasonable roduction in 1992. The other cultivars gave a very low production. In 1993, Denise lue and Caroline Blue again gave a good production and yielded large berries. Sharp- ue, Avonblue, and Caroline Blue had a relatively short harvest period. Production data p to and including 1995 are given in Table 50. fassification of the cultivars according to the harvest period arly : Sharpblue, '0 Neal and Cape Fear, arly to mid-season : Blueridge and Blue Rose, lid-season : Avonblue, Brigitta Blue and Denise Blue, lid-season to late : Caroline Blue. escription cultivars: ape Fear (United States) loderate but sufficient vigour. Open and compact habit, with healthy leaves. Berries reg, somewhat dark-coloured with somewhat insipid taste. lueridge (United States) loderate vigour. Open habit. Berries light-blue, solid, good taste. ) Neal (United States) loderate vigour. Open habit. Berries moderately large, solid, rather dark-blue, acid. arly flowering increases chances on spring frost damage. harpblue (United States) loderate vigour. Bushy, compact habit. Resembles in many respects Flordablue but srries are a bit darker in colour. Requires cross pollination. vonblue (Florida 1-3 x (Berkeley x (Pioneer x Wareham)) (Unites States) 3w vigour and bushy habit. Heavy pruning is required in order to avoid excessive fruit 3aring. Berries ripen about one to two weeks later than those of Sharpblue and ordablue and are a bit smaller than those of the latter. Appearance and quality very atisfactory. Self-fertile, but cross-pollination is recommended. enise blue (? x Bluehaven) (Australia) loderate vigour with upright, open habit. Berries very large, dark-blue with a rather rge calyx and a green 'bottom'. The taste is good. Tends to produce too many srries, and colours poorly around the stalk (remains somewhat red). Berries become jickly mealy after ripening. Berries loosen with difficulty from the stalk so that they at torn and a little 'flag' of berry skin remains stuck to the fruit stalk. The injury is a Dssible entrance for fruit rot. ue rose (x US S-52-H) (Australia) igourous grower with an upright habit. Berries large with a light-blue colour. Berries 69 A.R. 1995 Research Station for Fruit Growin too close together in the strings, so that picking is more difficult. In Australia the mos productive cultivar. Caroline blue (x Late Blue?) (Australia) Moderate vigour, healthy growth. Berries large, blue, with a good taste. Short harves period, which may facilitate mechanical harvesting. Brigitta Blue {? x Lateblue) (Australia) Vigourous growth and upright habit. Seems suitable for mechanical harvesting. Ligh blue very large berries with good taste. Table 50. Production data Cultivar Production in kg/bush 1992 1993 1994 1995 total Cape Fear 0.04 0.97 0.07 1.04 2.1 Blueridge 0.04 0.70 0.36 0.63 2.0 '0 Neal 0.51 0.29 0.74 1.6 Sharpblue 0.30 0.10 0.84 1.2 Avonblue 0.06 0.35 0.08 0.93 1.4 Denise Blue 0.15 2.01 1.48 1.32 5.0 Blue Rose 0.26 0.70 0.70 1.68 3.3 Caroline Blue 0.11 2.47 0.85 1.37 4.8 Brigitta Blue 0.06 1.58 1.18 1.57 4.4 Development of methods for an early and late harvest of currants raspberries, blackberries and blueberries W.A.G.M. Jansen Early and late harvest with blueberries in a mobile tunnel. In the spring of 1989, four early-ripening cultivars were planted, viz. Bluetta, Patrioi Bluejay, and Earlyblue. (Bluecrop was included as an example of a middle-seaso cultivar). In another part of the same block, zes late cultivars were planted, viz Berkeley, Dixi, Darrow, Coville, Elizabeth, and Elliott. Each spring, the early cultivar were covered by a mobile tunnel in order to advance the harvest. After the harvest c these cultivars, the tunnel was moved over to the late cultivars in order to retard th harvest time. In years with hot summers, retarding late cultivars proved difficult an sometimes the harvest period even coincided with those of the middle-season cultivar planted outside. Covering the early cultivars can give an advance in harvest date of tw to three weeks. Covering the late cultivars can render a retarding effect on harvest c one to two weeks. As far as advancing was concerned, Bluetta and Earlyblue in particular, satisfie 70 A.R. 1995 Research Station for Fruit Growing sgarding precocity and/or production. Bluejay did show too much growth for a tunnel ulture. Furthermore, Bluejay gave rather small berries. It proved difficult to determine ie right harvest time of Patriot, so that there is a chance of picking fruits with a green nderside. The risk of too early picking always lays in wait. or retarding, especially Darrow, Elizabeth and Elliott were satisfactory. Although arrow originally is not such a late cultivar as the other two, the quality of the berries jmained good. The same was true for Coville. This cultivar, however, was even earlier ïan Darrow. In 1995, the last berries of Darrow did not develop the right colour, roduction data up to and including 1995 are given in Table 51. able 51. Productiondata blueberry trial 1989 ultivar Production in kg/bush 1990 1991 1992 1993 1994 1995 tot. luetta 0.53 1.63 2.92 1.62 0.73 2.06 9.5 atriot 0.93 3.15 4.27 2.50 1.10 3.55 15.5 luejay 0.35 1.76 2.02 1.04 0.67 1.66 7.5 arliblue 0.40 1.85 3.26 1.95 0.53 2.31 10.3 luecrop 0.71 2.82 3.97 2.32 1.30 2.60 13.7 erkeley 0.05 0.47 2.80 0.58 2.50 2.33 8.7 ixi 0.03 0.43 1.66 0.95 1.62 1.40 6.1 arrow 0.25 1.42 0.94 0.94 1.00 0.71 5.3 oville 0.11 0.92 1.94 0.79 1.53 1.44 6.7 izabeth 0.23 1.88 2.96 0.94 2.48 1.50 10.0 lliott 0.06 1.28 1.98 0.99 1.59 0.83 6.7 ate harvest of blueberry by means of rain covers he average kilo price of the blueberry shows a downward trend during the season. A latively large quantity is supplied in a short period. Spreading the supply could have a ositive influence on the general price level. Supplies can be spread by the cultivar loice, by cold storage of the fruit, and by advancing or retarding the harvest by means f a plastic cover. Investigations showed that cooling blueberries is not easy. Therefore, ie other possibilities may be better options. 1994, covers were placed over parts of a plant density trial with eight-year-old ushes of middle-season cultivars Bluecrop and Coville. These were either grown as ee bushes or along supporting wires. In march 1994, two rows of two-year-old ushes of the very late cultivar Elliott were added to the trial. xcept for Elliott and bushes of Bluecrop, the production of the bushes under the rain ivers, was generally a bit higher than those that remained uncovered (Table 52). In sneral, the former also produced somewhat larger berries. The differences in producti- n and berry size between non-covered and covered bushes may be explained by the fferences in the climate. The temperature under the covers generally went up more owly. In very hot summers this has been favourable for the covered bushes. Further- ore, berries under the cover could be kept longer on the bushes (Table 53). So, they 71 A.R. 1995 Research Station for Fruit Growin had a longer period to grow out properly. Possibly, in less hot summers, berries coul even stay longer on the bushes, without loss of quality than in the experimental year. Table 52. Production data blueberry under cover 1995 With cover Without cover kg/bush average fruit kg/bush average frui weight (g) weight (g) Bluecrop Bush 3.7 1.3 4.6 1.2 Hedge system 4.5 1.2 2.9 1.1 Hedge system/filler 3.1 1.8 2.4 1.3 Hedge system/filler 3.9 1.4 2.5 1.5 Coville Bush 4.0 1.1 1.8 1.4 Haag 3.1 1.4 2.7 1.1 Struik/wijker 3.2 1.5 1.1 1.6 Haag/wijker 3.0 1.5 1.4 1.3 Elliott Struik 0.5 1.5 0.5 1.4 Table 53. Production data blueberry under cover 1995 Mean harvest date (50% of the harvest is picked) with cover without cover Bluecrop Bush 13 August 24 July Hedge system 12 August 25 July Bush/filler 12 August 24 July Hedge system/filler 12 August 23 July Coville Bush 14 August 4 August Hedge system 13 August 4 August Bush/filler 14 August 4 August Hedge system/filler 14 August 4 August Elliott Bush 29 August 22 August 72 A.R. 1995 Research Station for Fruit Growing .ate harvest and the effect of soil treatment with Elliott i december 1994, five-year-old container-grown bushes of the very late ripening ultivar Elliott have been planted under rain covers or in the open. The purpose of the ain covers was to retard the harvest in order to spread supply. In both treatments, half f the bushes were planted in a plant hole filled with peat and the other half were lanted in a trench with peat. irst berries were harvested in 1995. The production per bush was very variable, iushes under the cover could be picked 6 days later than those without a cover. This 3ad to somewhat larger fruit size (Table 54). able 54. Production data cover trial with Elliott 1995 With cover Without cover g/bush av. fruit mean g/bush av. fruit mean weight (g) harvest weight (g) harvest date date (50%) (50%) lush normal 322 1.4 28 Aug. 359 1.5 22 Aug. lush trench 481 1.5 28 Aug. 289 1.6 22 Aug. conomics and Farm Management Analysis itegrated fruit growing I.J. Groot 1995, only one trial on integrated fruit growing remained at one location, the xperimental garden at Zeewolde, due to the closing of the experimental garden at lumansdorp where the second trial was located. The technical aspects and results are escribed on page ***. The three systems are: I = current, II = integrated and III = linimum crop protection. The results of the three systems of fruit growing in 1995 ave been compared on economic terms. Only the differences in costs and returns, irectly related to the systems, were taken into account (Table 55). For costs this only oncerns costs for labour (fixed and casual) and for crop protection. The casual labour eeded for harvesting and grading largely depended on the cultivar, since there were irge differences in production levels. The tables show averages (costs and returns) per /stem, based on the average production per system. he calculation of the returns was obtained by multiplying the production per cultivar rith the price per cultivar, per quality class, based on a long-term average (namely 990/91 - 1994/95, prices 1995/96 were still unknown at the time of writing). Thus ie calculation of the returns was based on the quality of the production. 73 A.R. 1995 Research Station for Fruit Growini Table 55. Returns and costs of three systems of fruit growing, 1995, expérimente garden Zeewoide (guilders/ha) System I II m_ Returns 40.697 35.553 37.402 Costs fixed labour 8.823 8.769 10.065 casual labour 12.869 11.336 12.383 crop protection 1.417 1.807 1.223 The minimum system III had high costs for fixed labour because this system needed 4: hours more than the current system I for culturing activities and 32 hours more than th integrated system II. Extra labour was needed for thinning and treatment for cancer. Table 56 shows the results (returns minus the costs for crop protection, fixed am casual labour) for the three systems and the present value of the accumulated results o the years 1990-95. The used rate of interest for the present value calculation wa 5.5% Tables 55 and 56 give the averages of the eight apple cultivars involved. Generally i was true that each cultivar reached the best results in the current system I and th poorest results in the minimum system III, with two exceptions: with Elstar and Cox' O.P. the results in the minimum system III were better than in the current system I, bu lower than in the integrated system II. As yet this can not be properly explained. Table 56. Results (returns - costs for crop protection, fixed and casual labour) for th period 1990-1995, for 3 systems, Zeewoide (guilders/ha) System I M III 1990 -5.799 -8.337 -9.496 1991 -2.118 -2.636 -5.460 1992 17.926 18.922 10.254 1993 14.628 13.713 14.997 1994 16.808 15.968 14.297 1995 17.588 13.641 13.731 Present value total result 47.782 41.171 29.361 74 A.R. 1995 Research Station for Fruit Growing Decision support systems in fruit growing VI.J. Groot and K.E. Arends (trainee) \ decision support system for economie and ecological calculations n 1993, the development of a farm model was started, combining economie and ïcological calculations, with the aid of J. Bremmer, trainee of the Agricultural University )f Wageningen. As stated in the annual report of 1994, the first results of the model nade it clear that the model appears to be a good instrument. Therefore, the development of the model was continued in 1995, by translating the model from Lotus o Microsoft Access with the aid of K. Arends, trainee of the "Streekschool West- Brabant". The reason for this translation was that the model was too large for Lotus and became, therefore, less user-friendly. The model consists of two parts. The first part, the gross margin part, is completed in he new format. This part is able to calculate, for an apple or pear planting, the gross nargin and some effects on the environment of culture practices. The latter are xpressed in: use in kilos of active ingredients, spraying index (quantity used divided by quantity advised by the Extension Services) and the environmental impact points according to the environmental yardstick for the effect of pesticides on water life, soil ife and ground water in spring and autumn. The results of the gross margin calculation depend on cultivar, planting density, planting year and calculation year, system of crop )rotection (three possibilities according to the earlier mentioned trial with integrated ruit growing), type of water supply and costs of plant material. The environmental iffects depend on the system of crop protection, spraying technique, the presence of a Jitch, a windbreak and/or a path between ditch and planting. The calculations are made or three systems of crop protection. It is also possible to calculate the results if in the uture a levy on crop protection should be imposed. Such a levy could be imposed per cilo of active ingredient, on the price of the pesticides or per environmental impact )oint. The second part of the model is a holding model in which data for an entire holding are concerned. Because apple and pear plantings are of a perennial nature, the model can nake calculations for up to 15 years. This part calculates the effects on the entire ïolding and therefore includes the costs for labour, machines, land and capital amongst )ther things. The development of this part of the model will be continued in 1996. The iim is to publish a brochure on this model by the end of 1996. rice and quality \A.J. Groot, A.J.P. van de Waart (IKC-L, afd. Fruitteelt), B. Nieuwenhuize (trainee) 'rice differences in apple n the annual report of 1994, an initial research into the relationship between prices and :olour of Elstar and Jonagold was described. It showed large price differences between ipples within quality class I. These differences were caused by varying combinations of 75 A.R. 1995 Research Station for Fruit Growinc red and green colours. In 1995, this work was continued. In that year, the data used came from more auctions (all the large fruit auctions) and concerned the part of the supply sold in large lots divided by quality classes; and these lots mostly contair production from more growers. The data does not include the apples which are sold Table 57. Relative prices of 6 cultivars, different qualities within class I, three period: in 1994 (100% = average price class I) |-1 1-2 1-3 Super Top January - March Cox's O.P 123 100 89 Golden Delicious 123 102 90 126 Jonagold mutants 110 98 87 93 Jonagored 113 99 90 121 Rode Boskoop 114 102 86 Elstar 112 103 82 136 Red Elstar 107 101 87 145 April - end season Cox's O.P. 133 99 94 Golden Delicious 119 101 95 110 Jonagold mutants 116 100 92 108 Jonagored 106 99 103 96 Rode Boskoop 125 99 91 Elstar 108 102 91 Red Elstar 134 100 90 Start season - December Cox's O.P. 108 92 121 Golden Delicious 113 93 156 Jonagold mutants 105 99 Jonagored 105 93 114 Rode Boskoop 107 94 11 € Elstar 113 92 12E Red Elstar 1Œ7 93 10E through mediation of the auction, but only those sold publicly in front of the auction clock. The data used is from the year 1994, and therefore does not represent a whol< supply season. Comparison of the data with that of the Product Board for Fruit anc Vegetables shows that the data used concerned one third of the total sold natione supply of apples. The data concerned the supply of different growers sold together. This supply wai always divided into the different colour classes (three for blush: red, half-red and no red, and three for ground colour; green, green/yellow and yellow). The data is divide( into three periods : January - March, April to the end of the season and the beginninç of the season to December. In December the quality classification changed. 76 A.R. 1995 Research Station for Fruit Growing luafity and price "able 57 shows a change in the relative prices of quality class 1.1 after the change in he quality system. The best part of the old class 1.1 was changed into TOP quality. The lest part of the old class 1.2 was moved to class 1.1 and 1.3 was made obsolete and livided into 1.2 and 11.1. Therefore, the differences between class 1.1 and 1.3 (old) and 2 (new) are smaller in the new situation. At the start of the season 1994/95 the prices Jiffered by between 10% and 15% of the average price for class I. >ize and price "he best prices paid for the cultivar Golden Delicious was for size 80-90 mm. With lonagold, Jonagold mutants and Jonagored no specific size made the best price, but he size had to be at least 70 mm. Rode Boskoop showed best prices for the sizes 75- 35 mm and 85-95 mm. Cox's O.P., Elstar and Red Elstar showed a preference for the izes 70-80 mm and 80-85 mm (for example Elstar, Table 58). 'able 58. Relative prices Elstar, 5 sizes, 3 periods in 1994 (100% = average price class I) 'eriod 1 2 3 iO-65 59 52 43 Î5-70 85 81 72 '0-80 111 115 108 10-85 115 121 124 (5-90 83 108 88 lolour and price i the case of the bi-coloured cultivars, higher prices were given for more blush and for green ground colour compared to a yellow colour. In the first period of the season, ox's O.P. and Elstar with a yellow ground colour also reached higher prices provided hat the blush was sufficient. The 9 different colour classes of Jonagold can be divided ito 3 groups based on price. Highest prices were made for the group with green/half sd, green/red and green-yellow/red and lowest prices for apples which were green- ellow/pale, yellow/pale and yellow/ half red. olden Delicious is not a bi-coloured cultivar. At the start of the season 1994/95 green pples of Golden Delicious reached a 22% higher average price than the average price f yellow apples. In the second part of the season 1993/94 this difference was smaller nd at the end of the 1993/94 season the green-yellow apples made the best price. As n example of the relationship between colour and price, data of Jonagold is shown in 77 A.R. 1995 Research Station for Fruit Growing Table 59. Relative prices of Jonagold class I, 3 periods in 1994 (100% = averagi class I) Not red Half-red Red Period 1 green 96 105 105 green-yellow 81 94 112 yellow 64 90 95 Period 2 green 94 103 102 green-yellow 80 98 105 yellow - 92 99 Period 3 green 104 105 120 green/yellow 80 98 105 yellow 63 82 88 Optimum harvesting time It is difficult to produce the combination of red apples of the right size and with a greei ground colour. Data of the last 5 years of apples picked at the Research station show! a growth of Elstar during the last weeks of the growing season of 1.6 mm per week The thinning method is important to obtain sufficient apples of the right size at th optimum harvesting time. The change from green (measured from the border of the tw< quality classes green and green-yellow) to yellow (the border between the two qualit classes green-yellow and yellow) strongly depends on the position of the apple in th tree. Averaged over the apples this period lasts 25 days. Delay in picking gives large apples (higher prices) but more yellow apples (lower prices). The optimum strongl' depends on the cultivar, other harvesting activities and planned storage time. Thi research shows equal prices for green/half red and green-yellow/red Elstar. A late harvest has advantages because apples are larger and the price difference betweei apples of the size 65-70 mm and 70-80 mm for Elstar in 1994 was about 25 cents pe kilo. If poor weather conditions only cause an increase in size but give no more blush the apples still make a higher price, but the price advantage is less because the fruit have a more green-yellow ground colour. The price advantage is lost if the apple acquire a yellow ground colour caused by a long storage period. Conclusions As stated in the introduction, the data used was based on the large lots sold before th auction clock. It may be expected that prices of the other supplies follow the sam pattern. It is clear that large price differences appear within apples of class I. This finding i important especially while the actual prices of apples are rather low. Régule calculations should be made, to see whether the higher costs of extra grading, extr picking labour and so on are followed by higher returns. 78 A.R. 1995 Research Station for Fruit Growing Dlant Nutrition and Fruit Quality Physiology :ruit ripening as affected by environmental factors during the jrowing season '. Tromp he effect of temperature at early and late stages in the season on some of the ripening nd quality criteria in apple. ^s a continuation of some experiments in 1993 and 1994 (Annual Report 1993, p. 88- !9 and 1994, p. 84-86), two new experiments with Elstar were carried out on the ffect of some combinations of temperature and period of exposure on the progress of ipening. In the first experiment potted trees were exposed to a day temperature of either 16°C r 22°C, during three successive periods (from full bloom) of six, eight and eight weeks, here were four combinations, 22-22-22 (in period 1, 2 and 3, respectively), 22-22-16, 6-22-22, and 16-22-16. Night temperature was 4°C lower throughout. Day length was 4 h. The vapour pressure deficit of the air was the same at all temperatures. From 15 r 16 weeks after full bloom (2-3 weeks before "normal" picking time), for five weeks, ruit samples were taken weekly. Immediately after sampling the following parameters vere recorded: weight, specific weight, ground colour, ethylene production, firmness, tarch value, sugar content and acid content. The marked effect of temperature in the first few weeks on fruit ripening, as found in revious studies, was also noted in the present experiment. As Figure 1 for fruit rmness and Figure 2 for ground colour show ripening around picking time at 16°C (in eriod 1) clearly lagged behind that at 22°C. It is surprising that the effect of tempera ure during period 3 on ripening depended on the temperature in period 1. At the post- loom temperature of 22°C fruits were firmer and greener when harvested at 16°C than t 22°C (compare 22-22-16 with 22-22-22). However, the temperature during period 3 ad very little influence on firmness and ground colour when the trees were exposed to 6°C in period 1 (compare 16-22-16 with 16-22-22). i the second experiment the season was again divided into three successive periods of ix, eight, and eight weeks. There were four temperature treatments. Day/night amperature in period 1 was always 22°/18°C and in period 2 either 16°/12°C or 2°/18°C. During the third period the trees were exposed to four different temperatures Bsulting in the following regimes: 22/18-16/12-18/9 (in periods 1,2 and 3, respective- i), 22/18-16/12-16/12, 22/18-22/18-22/18 and 22/18-22/18-25/14. The value 8°/9°C in period 3 was chosen in such a way that the number of degree-hours (>5 C) in that period was the same as that for 16°/12°C. The same holds for 25/14°C and 79 A.R. 1995 Research Station forFrui t Growin 22/18°C. Theremainin g conditions and records taken area s referred to inth e previou experiment. Firmness (kg) 8 7 h —A— 22-22-220C 6 "O 5 --ÙT- 22-22-160C 4 —•— 16-22-220C 3 —O- 16-22-160C 2 1 0 _i_ -L J_ _L 14 15 16 17 18 19 20 21 Weeks after full bloom Figure 4. Fruit firmness around picking time asaffecte d bytemperatur e inth efir s six weeks following bloom andi n the period around picking time fror week 14. _ Colour value 0 —A— 22-22-220C -5 --ÙT- 22-22-160C —•— 16-22-220C •10 --O- 16-22-160C •15 •20 J_ _L I 14 15 16 17 18 19 20 21 Weeks after full bloom Figure 5. Ground colour of fruits around picking time as affected by temperatur in thefirs t six weeks following bloom andi n the period around pickin time from week 14. About -20 and +10 correspond with hard-gree and completely yellow, respectively. 80 A.R. 1995 Research Station for Fruit Growing Firmness (kg) 8 7 6 —*— 22/18-16/12-18/9oC 5 h —&- 22/18-16/12-16/12oC 4 —•— 22/18-22/18-22/180C 3 —O- 22/18-22/18-25/140C 2 1 0 _L _L 15 16 17 18 19 20 21 Weeks after full bioom Fruit firmness around picking time as affected by exposure to different temperatures in the period from week 7 to 14 (counting from full bloom) and in the period around picking time from week 14. Colour value 5 _ A * 0 —*— 22/18-I6/12-18/90C /a/^-—jo -5 - iff' ^t er —Cr- 22/18-16/12-16/120C —<•— 22/18-22/18-22/18oC -10 —O— 22/18-22/18-25/14oC -15 ~ -20 I I I I I I 15 16 17 18 19 20 21 Weeks after full bloom Ground colour of fruits around picking time as affected by exposure to different temperatures in the period from week 7 to 14 (counting from full bloom) and in the period around picking time from week 14. About - 20 and +10 correspond with hard green and completely yellow, respec tively. 81 A.R. 1995 Research Station for Fruit Growin The results for firmness (Figure 3) and for the ground colour (Figure 4) are the onl ones given. Fruits at harvest were firmer at 1 6°C than at 22°C given during periods and 3 (compare 22/18-16/12-16/12 with 22/18-22/18-22/18). For ground colour ther was no difference. When in period 3 a large difference was introduced between da and night, this had hardly any effect on fruit firmness. The data suggest that in the case fruit yellowing was slightly retarded. Storage and Quality Prediction of optimum harvest date for long-term storage in appli and pear A. de Jager, F.P. M. M. Roelof s and J. Lieshout First picking date for direct consumption Aims and methods The aim of this project is to develop better methods for identification of unripe fruit an for the prediction of the earliest acceptable harvest date for the cultivars James Grieve Elstar and Cox. Materials and Methods Fruits were sampled weekly during the 4-6 weeks preceding the expected start picking. Fruit characteristics were measured directly after picking and part of th sample was allowed to stay at 20°C for one week (shelf life). Subsequently fru characteristics were measured again and a taste test was performed. Quality charact« ristics at harvest and after shelf life are weight, firmness, background colour, starch Table 60. Models for estimation of taste (T) of fruit of James Grieve, Elstar an Cox after one week of shelf life based on ground colour characteristic a, b and L at harvest; in the absence of red colour, a represents th green colour (chlorophyll), b represents the yellow colour (carotenoïdi and L general colour intensity. Cultivar Equation James < 70mm: T = -16 7 + 8.28a + 3.03b+ 5.88L + 0.1 79a2-0.032b2-0.045L2 Grieve > 70mm: T = -8.26-3.44a + 0.10b-0.20L-0.117a 2 Elstar < 70mm: T = -6.21 +0.23a + 0.21L > 70mm: T = -0.70-0.34a + 0.08L-0.017a2 Cox's < 70mm: T = 2.69-0.78a-0.038a2 O.P. > 70mm: T= 1.25-0.81 a-0.032a2 82 A.R. 1995 Research Station for Fruit Growing attern, sugar level and acid level. The taste test included judgement of overall cceptability and judgment of firmness, sweetness, acidity and ripeness. Correlation- etween taste and fruit characteristics at harvest was determined in order to findcha- acteristics at harvest with predictive value. 'esults in the basis of data collected in 4 successive years (1991-1994) models were eveloped for James Grieve, Elstar and Cox to predict the overall consumer acceptance fter one week of shelf life at 20°C from fruit characteristics at harvest. In 1995 these ïodels have been tested and the additional data were subsequently used to improve ie model. In table 60 the equations are presented. In a first attempt models were sleeted, based solely on colour characteristics a, b and L (Minolta colour meter). As a suit of the tests in 1995 a further improvement was achieved in all cultivars by iscriminating between diameters less and more than 70 mm. able 61. Results of the old and new testing system based on experimental data in the period 1991-1995 for different types decisions expressed as % of the total number of decisions including all samples ranging in taste value from 4 to 7. In the colour test samples with predicted taste values (T) lower than 5.5 are rejected. ultivar Testing Falsely Falsely Rightly system approved rejected judged ames Grieve starch 12 28 60 colour 15 10 75 star starch 0 54 46 colour 4 8 88 ox's O.P. starch 5 24 71 colour 11 11 78 able 61 shows the results of ripeness tests using these models compared to the old ist based on starch, ground colour and size. appears that methods based on the non-destructive measurement of groundcolour are ^ual to (Cox), better than (James Grieve) or far better than (Elstar) the traditional sstructive starch test to discriminate between unripe and sufficiently-ripe fruit for rect consumption. During the course of summer 1995 samples - both from rejected id approved lots - were collected at three auctions in the first two weeks of early jpply. Table 62 shows the results of the starch test and the colour test as judged by ie actual taste test after one week of shelf life at 20°C. Again the system works very 'ell for Elstar. For Cox the colour system does not increase the number of right scisions but the number of badly-judged approvals is diminished at the cost of the jmber of badly-judged disapprovals. For James Grieve the colour system, although not orking ideal, is better than the starch system. Since 1995 was a rather unusual year >r James Grieve, the absolute % of right decisions will be higher in most years. The jlour method will, however, always be better than the starch method, s a result it is almost certain that the auctions and the controlling bodies (KCB, AID) 83 A.R. 1995 Research Station for Fruit Growir Table 62. Results of the old and new testing system based on of samples take from auctions in 1995 as % distributions of types of decisions in tl first week of supply at the auction. Cultivar Testing Falsely Falsely Rightly system approved disapproved judged James Grieve starch 0 87 13 colour 0 61 39 Elstar starch 0 44 56 colour 6 6 88 Cox's O.P. starch 31 8 61 colour 15 23 62 will change their testing systems for immature fruit from the starch test to the coloi test. This test can be done very quickly using e.g. a Minolta 300 type probe. Tr ripeness test will be presented in a user-friendly package adjusted to the wishes of tr users. The envisaged testing system will be portable, consisting of the colour meter ar a laptop computer. This project was sponsored by the EU Optimum harvest date of apples for direct consumption and fc prolonged storage A. de Jager and F.P.M.M. Roelof s Aim The aim of this project is to develop good criteria and prediction methods for indicatir the optimum harvest date for long storage for all important apple cultivars and to assi: in the implementation of practical methods. Materials and Methods Three different methods to predict optimum harvest date for long storage wei compared in this approach i.e. (1) the harvest index method according to Streif, (2) tr meteorological method, and (3) the so-called T-method. Emphasis has so far been c method (1) and method (2). Observations in the context of method (3) have bee started in 1993. The harvest index method is based on a combination of sugar level, firmness and stare pattern. The three data are combined into a new variable, the harvest index, I, l = F/R*S where F is firmness (kg), R is refraction (%brix) and S is starch-iodir coloration pattern (1-10, 1= black and 10= -white). The experiments were carried out fruit growers orchards. For each cultivar 4-8 orchards were chosen representing tr existing variation in the region with respect to soil type and climate. The cultivars still 84 A.R. 1995 Research Station for Fruit Growing search in 1995 were Elstar and Boskoop. With Elstar a special experiment was inducted in two orchards in order to establish the influence of thinning on optimum arvest date. Three levels of fruit-bearing were established by hand thinning to 2/3 or '3 of the original number at the beginning of July. Starting about 6 weeks before the cpected harvest date, samples were collected of Elstar and Boskoop twice a week in der to measure not only sugar, starch and firmness but also weight, ground colour, ;id concentration and - around harvest date - mineral composition. Each sample, insisting of 25 apples, was picked from the region of the tree where apples for the st pick are supposed to be. By international agreement these apples were picked from e west side of the tree avoiding the top, the bottom and the inner side of the tree stimation of first pick). In the meteorological method the relationship is studied between the number of days Dm date of full bloom (DFB) to optimum harvest date (OHD) and the weather during uit development. Experimentally this means that in a number of orchards for each jltivar (1) DFB is registered, (2) weather data, especially temperature and precipitation e registered on a daily basis and (3) OHD is determined by comparing the quality after ^-storage of fruits from three different harvest dates. When after a number of years ifficient data have been collected a first attempt to fit the number of growing days to e weather conditions can be made in order to find a predictive formula. This method as studied for the cultivars Elstar, Cox and Jonagold. The so-called T-method was included in the research programme for the first time in 393. It was proposed by Stoll (Wädenswil, Switzerland) and is based on the observati- l that the number of days from time of T-stage to optimum harvest date is almost instant whilst the number of days from flowering to T-stage is rather variable. T-stage the situation in which a concave base of the fruit changes to convex. In this interme- ate stage the stalk forms a T with the fruit base. Optimum Harvest Date can be ilculated by sampling fruit during three consecutive weeks (estimated optimum in the iddle) and using the harvest index method, or by actually storing the fruit and tablishing OHD following storage and shelf life. îsults irvest Index Method illowing the introduction in 1994 of a model predicting the regional optimum harvest ite of Jonagold similar models were introduced in 1995 for Elstar, Boskoop and Dlden Delicious. For Cox the harvest index at optimum harvest date can be established it prediction appears to be a problem. For Elise, a new promising cultivar, the best dication of optimum harvest date is given by firmness. The present knowledge is mmarized in table 63, showing harvest index value at optimum harvest date and the edictive equation allowing calculation of the expected optimum harvest date from ree to two weeks before the actual start of the harvest. The Dutch extension service -V has organised the 'harvest date warning' in the season 1995 - in co-operation with e auctions - on a national scale in the following way. Depending on the degree of gional variation 4-8 orchards were selected for each cultivar in 5 main regions. Fruit mples were collected each Monday from each of these orchards starting 4-5 weeks fore the expected optimum harvest date. These samples were transported directly to central location (auction of Geldermalsen) where firmness, sugar concentration (TSS) 85 A.R. 1995 Research Station for Fruit Growin Table 63. Mean Harvest Index Value (I) at Optimum Harvest Date and Predictin Equation (IM = number of days to Optimum Harvest Date). Cultivar I Predictive Equation Elstar 0.31 N = -17.1 + (55.1 * index) Cox's O.P. 0.25 prdeiction unsatisfactory Boskoop 0.26 N = 34.8 + 26.0 * ln[index]) Elise 8.64 kg N = -137.7 + (15.9 * firmness Jonagold 0.078 N = 49.2 + (19.3 * ln[index]) Golden Delicious 0.103 N = 39.9 + (17.5 * ln[index]) and starch degradation pattern ('lugoltest') were measured. Results were disseminate Tuesday or Wednesday by telephone service (growers), and by fax (co-operatives/o hers). Models in table 63 are implemented in the package PLUKY already containing th prediction system for Jonagold(BODATA). In tables 64 and 65 the influence of th degree of thinning on harvest index value and single fruit characteristics is shown i two different locations. From both tables we can draw the following conclusions. (1) Harvest index value was no higher in 'unthinned'; in both orchards a type c optimum is indicated, suggesting that both 'no thinning' and 'heavy thinning stimulai ripening. (2) This was almost completely caused by the apparent effect of thinning on the stare pattern; in both orchards both thinning and 'no-thinning' seemed to stimulate stare degradation. (3) Weight (and of course also size) of the fruit is clearly influenced by thinning. It interesting to note that this effect was smaller in the orchard with a more open type < tree even with a higher initial number of fruits per tree! (4) The treatment hardly affects firmness and firmness levels are no higher in 'unthit ned'. There is even a tendency to a lower firmness in 'unthinned'. (5) Thinning affects the green component of the ground colour negatively. It uncertain whether this is due to a lower concentration of chlorophyll or an increase amount of anthocyanin. (6) The acid concentration and the sugar concentration are affected positively b thinning. (7) % blush is stimulated by thinning in one orchard but not in the other. Summarizing these effects it appears that late hand-thinning does not advance ripeninç that fruit weight is increased, that fruits contain more acid and more sugar whil: firmness is no lower. In fact the only negative effect of thinning is an apparent decreas in the green component of the ground colour. Influence on % blush is not clear. T-stage Data of the past three years are summarized in table 66. Optimum harvest date he been estimated using the prediction method, rather than data from post-storaç evaluation, in order to include the third year. According to this data it seems th; variation between years of the number of days from T-stage to OHD is small for moi 86 A.R. 1995 Research Station for Fruit Growing piltivars, especially Jonagold, whereas for Golden Delicious variation is very wide. In der to establish whether this is due to an occasional deviation or characteristic for the jltivar, these observations have to be continued for a number of years. The Swiss ata represents the mean of 10 years! Comparison of our data with the Swiss data lows that differences are too large to continue using the Swiss data for Dutch able 64. Change over a period of time in the harvest index and single fruit characteristics of Elstar at three levels of fruit-bearing, (1) unthinned, (2) 1/3 thinned and (3) 2/3 thinned in a commercial orchard (grower A). Time of thinning was beginning of July. ro- 02-08 09-08 16-08 23-08 30-08 06-09 13-09 er A pick 1 pick 2 pick 3 pluk 4 arvest index (Streif) ) 0.82 0.74 0.70 0.60 0.30 0.31 0.16 :) 0.88 0.84 0.70 0.63 0.56 0.36 0.22 !) 0.89 0.77 0.66 0.63 0.41 0.37 0.14 uit weight (g) ) 82 83 91 98 110 117 120 !) 104 118 132 134 164 170 179 !) 101 114 132 142 168 169 179 rmness (kg) ) 8.5 8.5 7.8 7.5 7.0 6.6 6.2 :) 8.9 8.7 7.6 7.5 7.0 6.8 6.4 i) 9.0 8.5 7.6 7.6 7.0 6.8 6.2 roundcolour (-a-value) ) 18.4 18.3 17.6 17.8 15.4 15.3 13.4 :) 19.0 18.5 17.6 17.3 15.0 13.9 9.8 ) 18.8 17.5 17.3 17.4 15.4 14.3 9.2 tarch discoloration stage ) 1.0 1.12 1.00 1.08 2.04 2.00 3.56 ) 1.00 1.00 1.00 1.00 1.12 1.80 2.64 ) 1.00 1.04 1.00 1.00 1.60 1.80 3.54 cid concentration (%) ) 0.92 0.87 0.92 0.80 0.77 0.73 0.67 ) 1.12 1.04 1.04 1.00 0.95 0.90 0.84 ) 1.06 1.03 1.07 0.95 0.91 0.89 0.85 jgar concentration (%) ) 10.4 10.8 11.2 11.9 12.1 12.6 12.7 ) 10.1 10.4 10.9 12.0 11.7 12.3 13.5 ) 10.1 10.9 11.5 12.0 12.1 12.0 13.7 blush ) 22.2 43.9 ) 19.7 49.3 ) 22.0 54.2 87 A.R. 1995 Research Station for Fruit Growin Table 65. Change over a period of time in the harvest index and single fru characteristics of Elstar at three levels of fruit bearing, (1) unthinned, (2 1/3 thinned and (3) 2/3 thinned in a commercial orchard (grower B Time of thinning was beginning of July. Gro- 02-08 09-08 16-08 23-08 30-08 06-09 13-09 wer B pick 1 pick 2 pick 3 pick 4 Harvest index (Streif) (1) 0.88 0.79 0.72 0.62 0.43 0.24 0.22 (2) 0.89 0.84 0.67 0.64 0.58 0.43 0.29 (3) 0.97 0.79 0.72 0.61 0.52 0.22 0.16 Fruit weight (g) (1) 83 85 101 108 123 141 143 (2) 98 106 117 136 141 153 156 (3) 100 107 120 142 141 156 166 Firmness (kg) (1) 9.0 8.5 8.0 7.5 6.8 6.4 6.3 (2) 9.1 8.8 7.5 7.5 7.1 6.8 6.4 (3) 9.4 8.9 8.3 7.5 7.5 7.1 6.7 Ground colour (-a-value) (1) 18.5 17.6 17.9 17.5 15.4 13.5 11.5 (2) 19.0 18.8 18.2 17.5 15.3 14.4 13.0 (3) 19 18.8 18.0 17.7 15.2 13.4 6.6 Starch discoloration stage (1) 1.00 1.00 1.00 1.00 1.60 2.48 2.58 (2) 1.00 1.00 1.00 1.00 1.08 1.48 2.00 (3) 1.00 1.00 1.00 1.00 1.36 2.64 3.32 Acid concentration (%) (1) 1.02 0.97 0.99 0.90 0.82 0.76 0.77 (2) 1.08 1.06 1.03 0.96 0.92 0.90 0.82 (3) 1.11 1.11 1.02 1.01 0.96 0.92 0.85 Sugar concentration (%) (1) 10.2 10.8 11.2 12.0 12.1 13.0 13.4 (2) 10.2 10.4 11.2 11.6 11.9 12.6 13.1 (3) 10.8 11.2 11.5 12.3 12.9 13.4 14.8 % blush (1) 21.6 56.0 (2) 12.1 41.0 (3) 34.7 49.0 conditions. In particular Golden Delicious and Boskoop seem to mature faster in ou climate, whereas Cox and Jonagold mature faster in Swiss conditions. An alternativ explanation for these unexpected differences is that criteria for Optimum Harvest Date in Switzerland are rather different (different consumer preference?)! Since this type c research will be continued, mean figures for every cultivar will improve every year. 88 A.R. 1995 Research Station for Fruit Growing fable 66. Number of days from date of T-stage to optimum harvest date James G. Elstar Cox Boskoop Jonagold Golden D Jetherlands 993 79 96 100 114 124 107 994 84 99 99 117 126 116 995 78 102 105 119 124 117 /lean 80 99 101 117 125 113 Switzerland 77 - 95 125 120 121 Meteorological Method Sased on 6 years of observations a preliminary model will be attempted in spring 1996 year 5 of eurofru) for the cultivars Elstar, Cox's O.P. and Jonagold of the relation »etween the number of days from full bloom to harvest on the one hand and (1) date of ull bloom, and (2) temperature and precipitation until harvest on the other hand. rhis project was sponsored by the EU. Distribution of fruit quality in the tree at harvest and post-harvest >ehaviour in relation to the effect of fruit position in Elstar \. de Jager and J. Blaszczyk lim he aim of this project is to identify the degree of heterogeneity in the tree due to age if the fruit bearing wood and to position in the tree, in order to develop - if possible - nethods for growing (pruning, thinning), harvesting and storage which increase the vel and uniformity of fruit quality. flethods i two different orchards 9 trees were selected and all apples were numbered with a mall sticker adhering to the stalk. For each apple the position in the tree and wood age vas recorded. Six positions were distinguished i.e. top, inner, and outer where outer vas divided into east, west, north and south. Three age categories of fruits were istinguished i.e. top and lateral fruits from 1 year old shoots (1yT and 1yL) and fruits rom two year old or older wood (2y). At three dates - optimum harvest date, one week before and one week later - all ruits from three trees were picked. Trees were allotted to each harvest date according o the number of fruits in order to ensure equal distribution over harvest dates. Total ruit number ranged from 105 to 160 fruits per tree. In both orchards the trees were in he outside row of a 4-row system. Orchard A is characterized by north-south Oriental in, light soil (22% < 50 mu) and vigorous growth. The experimental row was exposed 89 A.R. 1995 Research Station for Fruit Growin to the east. Orchard B is characterized by east-west orientation, rather heavy soil (42S < 50 mu) and slow growth. The experimental row was exposed to the north. Table 67. Summary of the influence of position and wood age on fruit character^ tics and of the influence of storage and shelf life on these effects; - and - indicate nature of effects and A, B the orchard; positions: T(Top l(lnner), N(North), S(South), W(West), E(East); wood age: 1yT, 1yL, 2y Characteristic Position Wood age Storage/shelf life Number Top + (A,B) 1yL + no effect Inner + (A) Weight Top + (A,B) 1yT + (A,B) some changes N,E - (A,B) (only pick 3) in position effect Firmness no effects 1yT > 2y (A,B) no effect (pick 1 en 2) A-value Top - (A,B) 2y < 1y (A,B) no effect (only pick 3) Refraction Top + (A,B) 1y > 2y (A,B) no effect Inner - (A,B) (esp. pick 3) Acid concentration Inner + (A) 2y > 1y 2y < 1y !! (esp. pick 3) Starch pattern Top + (A) pick 1: 2y > 1y does not apply pick 3: 1y > 2y Streif-index Top + (A) pick 1: 2y < 1y does not apply Inner - (A) pick 3: 1y < 2y % blush Top + (A,B) 1yT + (A,B) slight increase Inner - (A,B) - 2y - (A,B) Following harvest, fruits from each tree were divided into three equal lots according t green ground colour on the basis of prior colour measurement of a-value (a*b* principle). Two lots were put into storage for evaluation of the effects of storage an shelf life. One lot was used for direct measurements at harvest. The following characte ristics were measured per single fruit: % blush, diameter (both with AWETA visio system), weight, colour (a*b*L, Minolta), firmness (in ground colour, INSTRON refraction (% brix, at conus penetration point), starch discoloration stage (1-1( 1 = black), and for every third fruit the % brix and % malic acid were measured an expressed as a mean of the whole fruit. In order to test the hypothesis that quality (here firmness and %brix) is related to th 90 A.R. 1995 Research Station for Fruit Growing oncentration of nutrients, fruits were distributed into quality classes according to the irior measurements of firmness and refraction. Parts (sectors) from all apples in each lass were combined for subsequent mineral analysis. The following classes were reated: firmness*refraction (5), firmness (3) and refraction (3). Storage conditions should have been 1.5°C, 1.2% 02 and 2% C02. Due to technical iroblems this has not been achieved. Consequently loss of quality has been much reater than normal during storage up to March. Thus, the duration of shelf life was educed from the normal 14 days (7 days 10°C and 7 days 20°C) to 5 days 20°C. lesults )ata was analyzed for each orchard by analysis of variance using harvest date, position nd wood age as variables. Table 67 shows a summary of the effects, he general picture from this data shows that, despite normal chemical and manual ruit-thinning the greater number of fruit in both orchards results from 1 year old hoots, from which 50% are lateral type. 2y fruit is almost absent from the top whereas 1yT fruits are almost absent from the inner position. ruits from the top position are most blushed and fruits from the inner position least. In rchard A (vigorous growth) the inner position has as much as 30% of total fruits, all of nem less than 10% blush! Also 1y fruits form the top section show highest % blush nd 2y fruits lowest. legarding other characteristics apples from the top section generally weigh more and ave less green ground colour and higher refraction, whereas apples from the inner ection have lower refraction and higher % acid. These effects are much larger in rchard A (more shade, vigorous growth) than in orchard B. In contrast to the influence f position, the influence of wood age is present in both orchards. The general picture > that top fruits from 1y shoots show very rapid development in the two weeks before ptimum harvest date. Whereas differences shown by comparison with 2y fruits are ery small at first, the former fruits at harvest are much larger, sweeter, less acidic, less reen and more advanced in starch degradation and have much more red colour. In the Teantime 2y fruits are comparatively slow-growing. 2yL fruits are in an in-between osition. ince these results represent the picture for only one year they are provisional and care hould be taken when interpreting them. The following conclusions might be drawn. The position effect is dependent on tree form and light distribution and therefore on factors like pruning and growth vigour. These factors can be manipulated and thus heterogeneity due to position can be largely avoided. Effects of wood age are - on the contrary - intrinsic and result in better quality of 1y top fruits, at least as far as direct consumption is concerned. The influence on size is very interesting for cultivars with a relatively small fruit size such as Elstar, Rafzubin etc. In cultivars with a large fruit size emphasis might be on smaller 2y fruits. Storage aspects in relation to the different fruit types should be more closely stu died. It is tempting to think of the differences between ages in terms of source-sink relations in the tree where 2y fruits are in a better position at first (no competing 91 A.R. 1995 Research Station for Fruit Growirv shoots) but 1y fruits (especially the top fruits) are in a better position later on, after conclusion of shoot growth. If this explanation is valid then removal of other type of fruits should also eliminate the differences between the types of fruit. 5. Experiments comparing trees with only 1yT, or 1yL or 2y fruits ('monoculture') might serve to test this hypothesis, provided that enough fruits remain for normal bearing. 6. Increase in heterogeneity due to wood age might be diminished by specific thinning strategies Table 68. Qualitative rating (++ to -)of the degree of correlation between th level of quality and the fruit nutrient concentration at three picking date in two orchards; quality criteria are firmness (F), refraction (S) and F*S tot indicates the sum of + or - and ptot the potential maximum. Index Pick Orchard CA K Mg N P F&S 1 A ? ? ? B ? ? + .? 2 A ? ? B + + ? -? 3 A + ? -? B ? ? — i S 1 A ++ ? B ? ? ? ? ++ 2 A + ? - — B + 3 A ? — ? — B ? H 2 A ++ B + ++ + + ?? 3 A ? ? + —! B ? ? ?? tot +9 -6 -7 - 19 -7 ptot ( +32 ) (-32) (-32) ( 32) (-32) + + strong positive relation + positive relation — strong negative relation - negative relation ? no relation 92 A.R. 1995 Research Station for Fruit Growing utrient Relations he correlation between quality aspects and nutrients is summarized in table 68. The orrelation of nutrient concentration with quality level (see 'methods') was evaluated ualitatively from + + to —fo r all three pickings and both orchards. From this type of nalysis only a negative correlation between N and quality appears. a separate experiment correlation between position/wood age and fruit nutrient oncentrations was examined in a direct way. Extra trees were used in orchard A in the ame row as the other experimental trees. Three trees were used to collect fruit from ifferent positions and three trees to collect fruit from different wood age. Only 3 ositions were distinguished, taking the four directions in the 'outer' section together, he results are shown in table 69. The results clearly indicate that - in this orchard - the riner' position has larger fruit nutrient concentrations and lower % dry matter than the ositions 'top' and 'outer'. Comparing wood ages, 2y fruits show larger fruit nutrient oncentrations and lower % dry matter, though differences are slightly smaller. The -eatest effect is on N concentration (42% and 33%) followed by P concentration 8% and 14%). K/Ca ratio, not a valid indication of storability in Elstar, is lower at the ner position but not lower in 2y fruits. able 69. Nutrient concentration (mg/100 g fresh) and % Dry Matter (DM) at three positions and three wood ages as a mean of three trees (Elstar) Ca K Mg N P %DM osition top 3.66 119.7 5.41 44.0 8.85 15.1 inner 4.83 135.1 5.74 64.6 10.85 14.1 outer 3.97 118.0 5.36 45.2 9.22 14.5 ge 1yT 4.23 122.4 5.48 44.8 9.18 15.0 1yL 4.15 123.3 5.45 47.5 9.62 15.0 >=2y 4.53 130.3 5.68 63.4 10.97 14.4 ombining both types of information on fruit nutrient concentrations, we can conclude at, at least in orchard A, N shows by far the highest variation in concentration îtween positions and ages and is also the only nutrient with a clear (negative) relation quality defined as a combination of sugar and firmness. Since no significant differen- is were established in firmness between positions and ages, this effect might be more sneral i.e. within positions and within ages. orrelations between fruit characteristics nee many fruit characteristics were measured on a single fruit basis it is possible to lalyze in a correlation matrix the mutual 'dependence' of all these characteristics. This is been done for both orchards and all picking dates. The results are summarized in ble 70. The following groups of fruit characteristics appear to be more or less upled: 93 A.R. 1995 Research Station for Fruit Growirv * PFW-index with starch, firmness, (sugar), Streif index, weight * a-value and %blush (and sugar) * L-value, a-value and Hue The b-value and acid concentration typically show no relation with any other measure* characteristic! Whether this has a meaning and can be used e.g. in quality or harves indices is not clear at the moment. It is striking to note that the PFW-index shows correlations with many more characters tics than the Streif-index. The original data shows that in Elstar, a cultivar that i harvested at the beginning of starch degradation, the Streif-index is very muc dominated by starch and shows very little correlation with firmness and sugar althoug these characteristics are included in the index! This might be good reason to re-evaluat the use of the Streif index and to consider its possible replacement in practice with th PFW-index. Table 70. Summary of correlations between fruit characteristics based on approx mately 900 fruits; W = weight, D= diameter. Su= sugar, Ac = acic hue= combination a- and b-value Characteristics Correlated characteristics weight + diameter a-value + % blush + sugar - L-value - hue b-value L-value + hue - a-value hue + L-value - a-value firmness + PFW-ind - weight - diameter sugar + a-value + % blush starch - Streif - PFW-ind Streif + PFW-ind - starch PFW-ind + PFW-ind + firmness - sugar - starch - weigh % blush + a-value - hue (+ ) sugar (+ ) Su/Ac diameter + gewicht - W/D acid - Su/Ac Simulated picking Data of the subsequent pickings was used to simulate three different picking strategie with respect to 'ripeness' of the remaining fruits. These strategies were pickin according to (1) fruit size, (2) % blush or (3) ground colour. Simulation was achieved by (1) defining critical values, (2) calculating what % of th fruits fulfilled the criterium, (3) removing this % from the next pick and (4) evaluatin fruit characteristics of the remainder. Critical values were 70 mm, 33% blush or a= -1J The results show that each successive pick is riper than the preceding one irrespe« tive of the method used. Although the method is very rough because of the tree to tre variation and the small number of trees involved, this result indicates that sequenti picking is not a good method for picking the fruits at an equal stage of ripening/storab lity. 94 A.R. 1995 Research Station for Fruit Growing )ptimum storage conditions and the suitability of storage techni- ues for fruit. P.MM. Roelof s im or a successfull introduction of new cultivars and mutants it is important to know the ptimum storage conditions and maximum storage period. The aim of this research is to ptimize storage conditions and storage period for new cultivars and mutants. ew cultivars uring recent years cultivar testing with apple has concentrated on scab- (and powdery lildew) resistant cultivars. The scab-resistant cultivar CPRO 78038-9 could be Dimparable to standard cultivars as fruit quality is concerned. lethod n September 13, 1995 (estimated optimum harvest date) fruits of CPRO 78038-9 'ere picked in 2 orchards: one was sprayed with a normal fungicide-spraying program- le, on the other was not. The fruits were stored at 3 different ULO conditions (1.2% xygen with 1%, 3% or 5 % carbon dioxide). On November 7, 1995 and January 31, 996 samples were taken from storage and quality was evaluated after 1 day, and after days shelf-life at 10 °C, and after another 7 days at 20 °C. esults t harvest the fruits from the no-fungicide orchard were a little less green and less firm ee also Figure 8). These fruits had a higher acid concentration (0.96 mg malic acid 00 ml juice) than the sprayed fruits (0.89 mg). The sugar concentration (12% Brix) as equal: The non-sprayed fruits had higher Potassium and Nitrogen contents and a wer Calcium content than the sprayed fruits. uring the first months of storage no loss of firmness was found; the firmness even :emed to improve in all storage conditions. Almost no disorders were found; only a w fruits with browning of the fruit flesh or core rot were found. In taste tests after 2 eeks of shelf life the fruits were judged 5.9 (1 = very poor; 9 = excellent). The taste as not affected by storage conditions or the spraying programme. onclusions PRO 78038-9 seems to store well in standard storage conditions. Firmness and ternal disorders were no problem up to February (more data is available now). The ste is not effected by storage condition and is quite well. No information is available i the effect of soil types and harvest date. 95 A.R. 1995 Research Station for Fruit Growin Firmness ink g 8 orchardan d% Carbo n Dioxidea t1° Can d1.2 %Oxyge n -»sprayed 1KC02 -»-sprayed 5%C02 ^non-eprayed 1% C02 +non-sprayed5 % C02 14-9 8-11 15-11 22-11 31-1 7-2 14-2 |95| |9S| |95| |95| |96| I96I |96| date Figure 8. Development of firmness during storage and sheli life of CPRO 78038- from a standard fungicide sprayed and a non-fungicide sprayed orchar under different storage conditions. Jonagold mutants Ever since the introduction of Jonagold, different mutants have been found. TH number of mutants is now so large that there is a need to select only a few standarc to avoid confusion in marketing. Two judgement criteria are optimum harvest dal (spread of work) and storability. Method The examined mutants were: Crowngold, Decosta, Jonagored, Jonaveld, King, Novajc Schneica B. and Wilmuta. Starting on September 20 in Zeewolde and September 13 Horst, 3 trees of each mutant were picked every week for 5 weeks. The fruits from tr external part of the tree (more or less first pick) were kept separate from the rest of tr 96 A.R. 1995 Research Station for Fruit Growing Harvestinde x 0.3 0.2 •*•Crowngol d "•"Decost a -*"Jonagore d 0.1 •*•Jonavel d ^ -•"King ""-^"k. '— i -*-Novaj o •*•Schneic aB ^Wilmuta 0.02 19- 9 26-9 4-10 11-10 18-10 Date Development of the harvest index of different Jonagold mutants in Horst in 1995. Harvest index -*-Crowngol d "•"Decost a "*"Jonagore d •*"Jonavel d "•"King "*"Novaj o •*•Schneic aB "•"Wilmut a 0.02 18-10 Development of the harvest index of different Jonagold mutants in Zeewolde in 1 995. 97 A.R. 1995 Research Station for Fruit Growin %- Fruits with 30%Blus h 100 """Crowngol d •*-Decost a •*•Jonagore d •*•Jonavel d -•"King •*•Novaj o "*•Schneic a B -*-Wilmut a 12-10 Figure11. Development of the percentage of fruits with at leats 30% blush i different Jonagold mutants in Horst in 1995. %- Fruits with 30% blush 100 -*-Crowngol d "•"Decost a "*•Jonagore d •*•Jonavel d -•-King -*-Novaj o "*•Schneic a B "+"Wilmut a 18-10 Figure 12. Development of the percentage of fruits with at least 30% blush i different Jonagold mutants in Zeewolde in 1995. 98 A.R. 1995 Research Station for Fruit Growing uits. From all fruits the area of blush and diameter were measured and other quality ïeasurements were done only on fruits from the external part of the tree. From each ick, fruits were stored at 1°C, 1.2% Oxygen and 5% Carbon dioxide. Judgement of uality will be done after storage. In 1996 comparable research will be done on Elstar nd Cox's O.P. mutants. 'esults i Figures 11 and 1 2 it is shown how the percentage of fruits with 30% blush develo- ed during the harvest period in Zeewolde and Horst. Blush developed quickest in onagored and Jonaveld, a little slower in Decosta, and from the rest Novajo seemed to e the best and Wilmuta to be the worst. The harvestindex of the different mutants eveloped almost equally (Figures 9 and 10). If all mutants have the same optimum arvest index, the optimum harvest dates will also be almost equal. i prototype of a computer model to describe development of ripening and quality has een made. his research will be repeated in 1996 in Zeewolde. 'his research was financed in 1995 by CBT. 'rediction of risk on superficial scald in Jonagold '. de Putter l 1994-1995 research was carried out to investigate the possibility of predicting afin n early stage scald occurrence after eight months of storage. Also under investigation tas the influence of ethylene on scald occurrence, onagold fruits were picked, at seven locations in the South West region of the etherlands, one week before the predicted optimum harvest date, from the outside îgion of the tree. Apples from each location were divided into four lots of approxima- îly 75 fruits. One lot was stored until January 9 at 200 ppm ethylene, and another at ppm ethylene, in a storage room. The other two lots were stored until May 22, one at 00 ppm and the other at 3 ppm ethylene in another storage room. Each storage room /as at a temperature of 1.2 °C with 3% 02 and 1 % C02. able 71. Storage scheme of Jonagold thylene January May untreated untreated 00 ppm 75 apples 75 apples 3 ppm 75 apples 75 apples t harvest and following storage firmness, fruit weight, L*a*b value, soluble solids and cid content were determined (Table 72). Also at harvest starch pattern was visually 99 A.R. 1995 Research Station for Fruit Growir rated on a scale from 1 to 10. At harvest and following storage the content of tr oxidants alpha farnesene (AF), measured at optical density 232 nm, and CTH, calcul; ted as the difference between absorption measured at optical density 281 nm and 29 nm, and the total anti-oxidant content, measured at optical density 205 nm (OD 205 were determined spectrophotometrically. The anti-oxidants vitamin C and vitamin were measured by HPLC. The oxidants are a possible cause of scald occurrence whi the anti-oxidants may be a factor inhibiting the scald occurrence. Following storac until May 22 the percentage of scald was determined after 3 weeks shelf life at 21 °C. Table 72. Quality measurements at harvest storage Harvest January January May May characteristics + C2H4 - C2H4 + C2H4 - C2H4 fruit weight (g) 178 174 174 173 171 L-value (intensity) 71.5 73.5 ab 73.7 ab 75.0 b 74.6 b a-value (green) -15.0 a -12.1 b -12.3 b -11.0 c -11.1 c b-value (yellow) 43.5 a 46.0 b 45.4 b 48.7 c 48.1 c firmness (kg) 8.2 a 5.9 b 6.4 b 4.6 c 5.1 c SS 13.0 a 14.6 c 14.6 c 14.0 b 14.3 b acid 0.7 a 0.6 b 0.6 b 0.5 c 0.5 c starch 4.96 - - - - streif 0.14 - - - - AF (nmol/ml/cm2) 0.67 a 44.7 c 44.9 c 32.3 b 34.6 b CTH (nmol/ml/cm2) 0.21 a 8.86 c 7.94 c 2.14 b 1.83 b OD 2059 (nmol/ml/cm2) 2.31 a 10.63 c 8.49 b 8.03 b 8.11 b Vitamine C (ug/100g) 19.9 a 13.6 b 15.1 b 9.9 c 11.2 c Vitamine E (ug/100g) 14.0 a 17.7 b 13.5 a - - Scald % 0 0 0 11.0 4.3 Values in one colomn followed by the same letter(s) do not differ significantly (P 0.05). L*a*b value = Ground colour measurement with a Minolta Chroma meter. L a value for colour intensity, a is a value for green colour and is a value for yellow colour. Firmness Firmness measured in kg with 11 mm probe SS soluble solids % Acid titrametrically measured percentage acid in apple juice Streif Firmness/(Starch*SS) AF, CTH, OD205 content in nmol/cm2 apple peel in 1 ml Hexane Vitamins C and E content measured in ug/100 g fresh weight The small amount of scald is striking although apples were picked early and stored i conditions favourable to the occurrence of scald. Only after storage until May wei scald symptoms visible after shelf life. Between storage at a high or low ethylene lev there was no significant difference in scald occurrence. Storage at low ethylene lev 100 A.R. 1995 Research Station for Fruit Growing owever, showed 7% fewer apples with scald symptoms. From the results it is also lear that storage period specially influences several fruit characteristics (table 2). torage at high or low ethylene levels seemed not to have a great influence on quality îctors and scald. Only vitamin E and OD 205 content are higher with storage at a high thylene level. It is also striking, that in storage at a low ethylene level firmness is 0.5 3 higher compared to storage at a high ethylene level. Also b value of apples stored at low ethylene level is somewhat lower than in apples stored at a high ethylene level, his means that apples stored at a low ethylene level are less yellow than apples stored Scald % 6.2 7.2 8.2 9.2 10.2 11.2 12.2 CTHcontan tI n January Maaaurad% +calculata d % gure 13. Relation between CTH content measured in January and scald percenta ge in Jonagold stored until May 22 at a high ethylene level. a high ethylene level. Apparently the content of different biochemical substances, ich as alpha farnesene, increases during the first period of storage until January and îcreases afterwards. No significant differences between storage at low or high hylene levels were present in the biochemical substances. jbsequently the relation between measurements at harvest and after storage until anuary on the one hand, and scald percentage after storage until May on the other md was investigated. From this it seems that CTH content in January was only ightly related to scald (Figure 13), but only when stored at a high ethylene level. From 3ure 13 it is also clear that measured points are not correlated very well with the ilculated regression line. Therefore CTH content in January is not a good parameter r scald prediction. Other relations of measured factors with scald were even worse. wsresearch was partly funded by the European Community. 101 A.R. 1995 Research Station for Fruit Growin Fungicide use reduction in spray scheme for controlling storage rot H. de Putter The aim of this research is to investigate whether and if so to what extent ULO storag inhibits storage rot as compared to regular storage. Apples were picked from trees the were not treated with fungicides after August 1 and from trees with a routine fungicid programme. After ULO storage the percentage rot was determined in both sprayed an non-sprayed apples. Results of those experiments in the seasons 1992-1993 and 199C 1994 showed that at ULO storage more rot occurs in non-sprayed apples compared t sprayed apples. Subsequently a second line of investigation was started concerning the influence c non-chemical treatments or methods on rot development in storage. In 1994-1995 three antagonists, Cryptococcus laurentii, Bacillus subtillus and Sporobc lomyces roseus, were tested for their influence on rot in fruits of Elstar and Jonagolc At three locations part of an orchard was not sprayed with fungicides from August for both Elstar and Jonagold. Sprayed and non-sprayed Elstar and Jonagold were picke on August 30 and October 6 respectively. Directly after picking, the non-sprayed apple were divided into 5 lots. One lot was drenched in clean tap-water, one lot was nc drenched and three lots were drenched in a water solution containing spores of one c the above mentioned antagonists. Elstar was stored until March 30 and May 11 Jonagold was stored until May 17 and July 7. After three weeks of shelf life at 21 °< percentage rot and the type of rot causing fungi were determined. Both Elstar an Jonagold also showed more rot this season in non-sprayed apples compared to spraye apples (table 73 and 74). It is surprising to find that percentage rot in Jonagold i extremely high in non-sprayed as well as in sprayed apples. Also compared to previou seasons more rot occurs as a result of infection by Nectria and Gloeosporium fung Percentage rot caused by Botrytis and Pénicillium is lower compared to previou seasons. Antagonists seemed to have reduced percentage of rot in Elstar. This is especially du to a reduction in the percentage of rot caused by Pénicillium and Botrytis. Rot cause by other fungi was not reduced by the antagonists. Since however, the contro drenched only in clean tap-water, also showed a reduced percentage rot compared t the non-drenched control the influence of the antagonists on rot is not clear. Antagc nists are also reducing the amount of Botrytis and Pénicillium rot in Jonagold. Since th largest amount of rot was not caused by those two fungi the total rot- reducing effec of the antagonists is not significantly different from non-sprayed apples. In a second experiment the effects of periodic C02 increases were tested on re suppression in Jonagold. A periodic increase of C02 in our test means an increase c carbon dioxide level to 20 % in the storage room during three days. It is known that C02 level of 20 % during storage of some other crops, like red currant, gives a larg reduction in percentage rot. Continuous storage of apples at 20 % C02 is not possibl without damage to the apples. For this reason periodic increases are tested for thei influence on rot suppression and on damage to the apple. Jonagold apples were picked at four locations and stored until January at 2 °C and 2 % 02. From January apples were transferred to ULO condition of 1.2 % 02 and 5 °, 102 A.R. 1995 Research Station for Fruit Growing able 73. Average percentage rot in Eistar after storage to 30 March and 11 May after 3 weeks shelf life at 20 CC Kind of fungi Botry Péni Gloeo- Nectria Rest Total tis cillium sporium jrayed 0.22 a 0.24 ab 0.05 0.21 0.13 0.86 a 3n-sprayed 0.85 b 0.34 b 0.22 0.56 0.33 2.30 b ater 0.25 a 0.22 ab 0.12 0.27 0.24 1.09 a 1 0.36 a 0.10 ab 0.17 0.41 0.16 1.18 a 2 0.33 a 0.12 ab 0.24 0.40 0.22 1.31 a 3 0.17 a 0.07 a 0.12 0.43 0.21 1.00 a alues in one colomn followed by the same letter(s) do not differ significantly (P < 05) 1 = Bacillus subtillus, A2 = Cryptococcus laurentii, A3 = Sporobolomyces roseus. able 74. Average percentage rot in Jonagold after storage to 17 May and 7 July, after 3 weken shelf life at 20 °C. Kind of fungi Botry Péni Gloeo- Nectria Rest Total tis cillium sporium »rayed 0.67 ab 0.34 ab 3.66 4.95 0.35 9.96 a )n-sprayed 1.13 b 0.11 ab 4.05 7.79 0.47 13.55 bc ater 1.94 b 0.41 b 5.36 7.09 0.54 15.34 c 1 0.79 a 0.06 ab 5.20 7.16 0.39 13.59 bc 2 0.59 a 0.16 ab 3.70 5.24 0.53 10.23 ab 3 0.51 a 0.02 a 3.85 6.14 0.47 10.98 ab alues in one colomn followed by the same letter(s) do not differ significantly (P < 05) 1 = Bacillus subtillus, A2 = Cryptococcus laurentii, A3 = Sporobolomyces roseus. C D2 at 1-5 C. Apples from each location were divided into 6 lots. One lot was intinuously stored at 1.2 % 02 + 5 % C02. In three treatments C02 level was creased during three days every two, three, or four weeks. In the fifth treatment C02 as increased the first day to 1 2 % and the second and third days to 20 % every two eeks. In the sixth treatment the oxygen level was also increased to 3 % in the jatment where C02 was increased every two weeks. After storage until May 15 ircentage rot and percentage of carbon dioxide damage were determined, j significant differences in percentage rot and percentage carbon dioxide damage 103 A.R. 1995 Research Station for Fruit Growin were present between all treatments. However, it seemed that more damage occurre when carbon dioxide was increased to 20 % every two weeks compared to every thre or four weeks. Table 75. influence of periodic increases of carbon dioxide to 20% on rot suppre: sin and carbon dioxide damage in Jonagold 1994-1995 Interval between increase of carbon dioxide to 20% gas condition control 2 weeks 2 weeks 2 weeks 3 weeks 4 weeks during C02 increase CO 2% 5 20 12 + 20 20 20 20 02% 1.2 1.2 1.2 3.0 1.2 1.2 % rot 5.7 6.0 5.7 5.9 4.9 4.8 % C02 damage 2.7 13.9 11.5 12.6 5.7 10.6 Pre- and postharvest fruit quality in relation to nutrition and othc orchard factors. H. de Putter and A. de Jager Firmness of apples is an important criterium for determination of fruit quality. Durir storage and shelflife however, firmness decreases more or less rapidly. In a joii research by ATO-DLO and our institute a model has been developed, 'Q-Apple', th predicts the loss of firmness of Elstar apples in general. The question is now to wh extend individual orchard deviate from this 'mean development' due to difference especially nutrition, but also other orchard factors. To investigate the possibility f< prediction of the firmness of apples after storage research is carried out to detect possible relation between mineral content of apples and firmness in Elstar and also Rode Boskoop, Cox's Orange Pippin and Jonagold. In August 1994 were 40 to 6 samples picked, from different locations for each cultivar, in the South Western regie of the Netherlands. Mineral content was determined in a sample picked approximate two weeks before picking as usual in the practical system for prediction of storac disorders. Crop load, vigour, silt % and trees/ha were also determined. At pickir another sample was taken for determination of fruit weight and firmness. The remainir apples were stored at ULO conditions and after storage fruit weight and firmness we measured directly after storage, after one week shelflife and after two weeks shelflife 20 °C (Table 76). Fruits were stored commercially, Boskoop until February 8 in 199 Cox until November 18 in 1994, Elstar until May 11 in 1995 and Jonagold was store until May 16 in 1995. The results showed that, as an average of all samples per cultivar, mineral content Boskoop is too low (Table 76). For Cox the average content of calcium, potassium ar nitrogen is medium and for phosphate and magnesium the average content is slight 104 A.R. 1995 Research Station for Fruit Growing oo low. The average mineral content of Jonagold is normal. In the Netherlands there re no standards yet for mineral content of Elstar at harvest with regarding to storabili- Compared with the standards for Cox calcium-, potassium- and magnesium content would be medium while nitrogen content is too low and phosphate content is too high, or each variety the decrease in firmness during storage is rather high. Even Jonagold pples showed a decrease in firmness of 2.5 kg. 'able 76. Average values for mineral content, firmness at harvest, firmness at take out and firmness after two weeks shelflife. Content (mg/100g fresh weight) Firmness (kg with 11 mm probe) lultivar Ca K Mg N P picking take out 2 weeks loskoop 4.1 99 4.7 41 9.4 8.0 5.0 4.2 )ox 5.4 136 6.5 64 12.8 8.7 5.8 5.2 Istar 5.2 119 5.5 42 11.0 7.5 5.6 3.5 onagold 4.4 112 5.3 43 9.8 7.6 4.9 4.3 'able 74. Best models for explaining the present variance in decrease of firmness during storage. Df = Decrease of firmness during storage oskoop R2 = 84% if = 0.59 + 0.47xfirmness at picking - 0.43xCa + 3.2x10"4xtrees/ha ox R2 = 54 % if = 2.77 + 0.58xfirmness at picking + 0.06xcrop load Istar R2 = 50 % if = -1.01 + 0.71xfirmness at picking - 0.08xK/Ca + 0.02xK - 0.44xCa onagold R2 = 29 % ).56 + 0.52xfirmness at picking - 0.16xCa l Table 76 only average values are given of all locations were samples were taken, ifferences in mineral content and firmness between the locations were present in a ange from very low to very high values. On base of analysis of the relation between lineral content and orchard factors on one hand and decrease of firmness on the other and models are made for prediction for the postharvest decrease of firmness. At each îodel a R2 is given which represents the amount of variance accounted for by the ïodel. The analysis shows that decrease of firmness is highly depending on firmness of ie apples at harvest (Table 77). A firmer apple at picking is also firmer after storage. A rmer apple however, has also a larger decrease in firmness compared to less firmer pples. ot all the models do, however explain the existing variance sufficiently. At Boskoop 105 A.R. 1995 Research Station for Fruit Growin Not all the models do, however explain the existing variance sufficiently. At Boskoo the present variance is explained satisfactorly while for Jonagold percentage varianc accounted for is unsatisfactory. Also the relation between mineral content and firmness was not for each variety th same. In Cox it seemed if only firmness at picking is important for decrease of firmness At Elstar and Boskoop it seems that besides firmness at picking also potassium an calcium are influencing the decrease of firmness. Calcium content has probably also a influence on decrease of firmness of Jonagold. While the present model does nc explain the present variance very well improvements might be possible. Beside decrease of firmness during storage also the relation between mineral content an decrease of firmness during storage including shelflife is investigates. From this analys almost the same models were found as for decrease of firmness only during storage. Reduction of internal disorders during storage of Conference pear. F.P.M.M. Roelof s Aim In co-operation with ATO-DLO, research on brown heart (cavities and browning of th fruit flesh) was carried out with Conference on the basis of earlier preliminary wor The aim of this research is to find the cause of the problem and to set up a practic system for analysing the risk of brown heart. Method In co-operation with the auction, 6 orchards were selected for sampling twice-week during a period of 7 weeks in order to follow ripening. The orchards differed in the pa in sensitivity to brownheart. During the last 4 weeks (starting on 6 September 199! larger samples were picked in order to examine the sensitivity to brownheart in differei storage conditions. In 2 orchards fruits from the external part of the tree were picked separate from tf rest to get an impression of the effect of position on the tree on brownheart. At each harvest the pears were divided into several equal parts and put into differei storage conditions: regular storage and 3 ulo conditions (2% oxygen and 0.5%, 1.5 or 3% carbon dioxide, all at -0.5°C). In a separate experiment pears were put in th stores and oxygen was lowered (after 0, 2, 10 or 21 days) to 2%. In conclusion, tv\ scenarios of pull-down were examined. Results Starting in November, regular fruit samples from the last pick (October 4) were tak* from storage to find the earliest stages of brownheart. Figure 14 shows that on November almost no internal disorders were found, except with some over-stored 106 A.R. 1995 Research Station for Fruit Growing percentage 100 ~*~healty •+•brow nfas e 1 ***brow nfas e 1+ 2 "*"brow nfas e 1+2+ 3 ~*~tota l brown "*"tota l cavities ~*~onl y cavities "*"cavitie s and brown "•"ove r stored 1 Nov 16No v 23 Nov 28 Nov 18De c 11Ja n 95 I 96 gure 14. Development of internal disorders at Conference, harvested at 4 October 1995, during the first month of storage at -0.5°C, 2% 02 and 0.5% CO, ears. Up to the end of November the amount of internal browning developed very fast, etween 18 December and 11 January 1996 the number of pears with cavities icreased rapidly. Figure 1 strongly suggests that the pears with cavities had also been rown since the number of healthy pears did not drop in the period that cavities eveloped and only the number of pears only with brown decreased. Whether cavities ways develop in severe brown fruits or also in pears with slight internal browning is ot clear, ecause most of the pears are still in store, no further results can be described here. his research is financed by "Productschap voor Groenten en Fruit (PGF)" and "Ministe- e van Landbouw, Natuurbeheer en Visserij (MLNV)". 107 A.R. 1995 Research Station for Fruit Growin Project 130: Skin spots on Elstar F.P.M.M. Roelof s Aim The problem of "skin spots" on Elstar has increased since 1990 and represents serious problem now. In 1992 research was started to solve this apparently Dutc problem, up till now without succes. The aim of this research is to identify factors th< influence the occurrence of skin spots on Elstar. Because the storage experiments mainly run until April, the following discribes resuli of trials started in 1994 and 1995. The effect of calcium spraying In practice different ideas exist about the causes of skin spots. The experiment wit calcium spraying can be considered as a test for the following idea: due the aggressiv effect of calcium chloride (CaCI2) the skin would be attacked, resulting in skin spoi during storage. Stip-Stop and calcium nitrate (Ca(N03)2) should give no damage. If th is true spraying in the evening should harm the fruits most because they remain wet fc a long period. Method In 1994 an experiment was done on parcel 17 at the Wilhelminadorp experiment station. Before the start of the experiment all trees had already been sprayed 3 time with Ca(N03)2. The treatments CaCI2, Ca(N03)2, Stip-Stop and water were carried out 2 replicates with "tween" and in 3 replicates without "tween". All treatments wei carried out with the maximum concentration according to instructions on the packe During the last 2 months before harvest (starting on 26 July) the treatments were dor weekly in the evening, just before sunset. All trees were sprayed until the trees wei completely wet. Each replication contained 5 trees with a good crop load. At the estimated optimum harvest date (harvest index method) all fruits were pickec Fruits with more than 30% blush were not included in the experiment. Fruits from tr east side of the tree were kept separated from fruits from the west side. Also tr solitary fruits were kept separated from fruits from a cluster. The fruits were stored until the end of March at 1.5 °C, 1.2% oxygen and 3% carbo dioxide. After 2 weeks at 20 °C (shelf life) skin spots were counted. Results The number of skin spots was classified in 5 groups: 0, < 1 cm2, < 2 cm2, < 50' and > 50% of the skin covered with skin spots. An index was made to analyse the c follows: index = (1 * group 1) + (2 * group 2) + (3 * group 3 ) + (4 * group 4) 108 A.R. 1995 Research Station for Fruit Growing olitary fruits have a lower skin spot index (79.9) than fruits from a cluster (124.8) .SD(P= 0.05) = 7.8). No effect of the spraying was found on solitary fruits. Fruits om a cluster sprayed with CaCI2 had a significantly higher skin spot index compared ) those sprayed with Ca(N03)2) and water. The Stip-Stop treatment didn't differ from ie other treatments, higher skin spot index was found on fruits from a cluster from the east side of the ee (116.7) than on fruits from the west side of the tree (132.9) (LSD (P= 0.05) = 1.9). Solitary fruits from both sides didn't differ. onclusions olitary fruits have less skin spots than fruits from a cluster. Spraying with Ca has only :tle effect on skin spots. The largest effect was found on fruits from a cluster. CaCI2 id Stip-Stop spraying gives some skin spots, but Ca(N03)2) none. An indication was >und that fruits from the east side of the tree are more sensitive to skin spots than uits from the west side. ffect of pull-down and speed of warming-up. xperiments in recent years showed the effect of storage conditions on skin spots. In ractice comparable fruits were stored at different locations under equal storage Dnditions but with different losses caused by skin spots. Sometimes the speed of pull- Dwn was the only apparent difference. There were also indications that a temperature nock induces extra skin spots. lethod he effect of pull-down and temperature shock was examined in a small storage higher skin spot index was found after a fast pull-down (254) compared to a slow ll-down (196) (LSD (P = 0.05) = 29.7). Some indication was found that a tempera- ire shock causes more skin spots. onclusions fith pre- and post-storage "treatments" different skin spotdamage can be induced, apid pull-down of oxygen gives extra skin spots on sensitive fruits. After storage extra amage may be prevented by slowly warming up the fruits. 109 A.R. 1995 Research Station for Fruit Growin Soil Science and Plant Nutrition Control of growth and production of pit and stone fruit by water am nutrient supply M.P. van der Maas Advisory system for the water supply The need for water in apple growing In order that advice may be available on a water supply system knowledge is needed aboi the desired water content of the soil which the system should aim for. The desired watt content is dependent upon requirements concerning shoot and fruit growth, fruit qualit and flower bud initiation. The desired water content is not the same for each soil. This i caused by different relations between water content and pressure head for different soils In a controlled experiment, in which trees were grown in covered pots of 30 litres, a stud was made of how apple trees respond to different pressure head levels during the shoe growth period (May up to July). For this trial the apple cultivar Elstar, on rootstock M.Ï was used (planted as three-year-old trees, planting distances: 50 x 200 cm, treatment were carried out in the second year of growth). The soil was a humic fine sandy soil. Th treatments were -4, -50 and -160 kPa. In the period preceding treatments the soil aroun the trees was maintained at -50 kPa and after the treatment period at -4 kPa. The treatments had statistically significant effects on shoot and fruit growth and o calcium, dry matter and starch content at harvest (see Table 78). The difference in stare value indicated that the optimal harvest date was 3 to 5 days later. No statistical! significant effects on the number of shoots, the number of fruits (average 20 fruits/tree blush percentage, ground colour, firmness, or on sugar, acid, Nitrogen, Potassiurr Magnesium and Phosphor content of the fruit were found. Blush intensity at -160 kPa wa lower (A-value of 21) than for the other treatments (A-value of 28). At harvest n statistically significant effect on dry matter content could be found (average conten 17,5%). The growth of shoots was optimal at -50 kPa (enough growth and flower bu initiation and hardly any pruning was needed). The growth of shoots ended two week earlier than at -4 kPa, while no extra re-growth was recorded after increasing the wate application. With -160 kPa the shoot growth ended four weeks earlier than with -4 kPî regrowth, however, occurred more frequently. An important observation was that in the pressure head range of -4 to -50 kPa the shoe growth responded more to the reduced water availability (when evaluating the effects i at harvest) than the fruits. This means that when there is a problem of excessive shoe growth the growth can be controlled under dry weather conditions by reducing the wate availability to some extent. Some reduction in calcium content and fruit weight (see tabl 78) and in sugar content should then be accepted. In this experiment no statistical! significant effect on sugar content at harvest was found. In literature however, an increas in sugar and dry matter content is mostly reported after reduced water availability (also se next session). In this experiment the dry matter content on July 27 was greatly affecte (see Table 78). 110 A.R. 1995 Research Station for Fruit Growing able 78. Effects of pressure head of the soil during the shoot growth period with Elstar ressure Water Shoot Fruit Calcium Dry matter Starch ead content growth weight content content value cPa) (%) (m/tree) fruits fruits fruits (g) (mg/100g) (27 July) *) .2 10 3.1 109 5.3 18.5 1.1 .7 15 6.4 148 4.1 16.7 1.5 .9 30 11.9 167 3.1 14.9 2.0 decolouring value ranging from 1 to 10 (high value: less starch) Xharves t (6 September) the dry matter content with -4 kPa was one dry matter percent iwer than with -50 or -160 kPa (this difference was however not statistically significant), ogether with the observation that the starch content at harvest was higher at -50 and - 60 kPa it can be expected that the sugar content after storage will be statistically gnificantly higher at -50 and -160 kPa. /ater project Zeeland n four farms in Zeeland in 1995 the effect of water application through trickle irrigation ) full grown trees was studied. The water was given based on experience of the growers nd with the help of the preliminary version of an advisory system WG-Meteo/IRRY for the rater supply. On average the water application started on 1 July and ended on September (water application: 160 up to 255 litres/tree). In this period hardly any rain fell and air mperatures were relatively high. For three of the four farms the water application resulted i a statistically significant increase in production which was related to an increase in fruit ze (see Table 79). With Elstar on farm C the percentage increase was the highest for all irms (29% higher production or 3.6 kg/tree extra). On farm B with Jonagold the actual /eight increase was the highest (4.5 kg/tree extra which is 12%). At farm D with onagold-Wilmuta the increase was 2.9 kg/tree (9%). For farm A no statistically significant icrease could be calculated: the extra 1.6 kg/tree could also have been a coincidence. The ifferences in increase in production between the farms can be explained by one or more f the following variables: leaf area, fruit load, rooting depth, ground water table, soil type nd precipitation. At farm C for instance the rooting depth was only 80 cm because of and occurring at this depth while the ground water table fell to 200 cm below the surface uring the summer. Because of this the trees could not benefit from rising ground water nd the applied water had a great effect. At farm A the rooting depth was 110 cm while ie ground water table did not fall below 180 cm and the soil had good water-rising haracteristics. Because of this the trees had ground water available during the whole sason and water application had hardly any effect. /ater application had an effect at the farms B, C and D. The following fruit characteristics rere affected (see Table 79): . Sugar content. On all three farms the restricted water availability resulted in higher jgar 111 A.R. 1995 Research Station for Fruit Growin Table 79. The effect of water application in July and August 1995 on four farms i Zeeland on the production and fruit characteristics of Elstar and Jonagolc Farm Production Fruit Firmness Calcium Starch Sugar /cultivar kg/tree weight content value content /water A. Jonagold -water 31.6 a *) 201 a 6.6 a 3.8 a 9.5 a 12.5 a + water 33.2 a 204 a 6.6 a 3.7 a 9.6 a 12.3 a B. Jonagold -water 35.8 a 177 a 5.9 a 3.9 a 9.8 a 13.2 a + water 40.3 b 191 b 6.1 a 3.4 b 9.9 a 12.4 b C. Elstar -water 12.8 a 137 a 6.8 a 3.8 a 3.9 a 14.9 a -(-water 16.4 b 162 b 6.4 b 3.9 a 3.1 a 13.5 b D. Jonagold -water 33.2 a 169 a 5.7 a 5.1 a 9.8 a 13.3 a + water 36.1 b 177 a 5.6 a 4.8 b 9.9 a 12.6 b *) a difference in character indicates that the water application had a statistical! significant effect **) decolouring value ranging from 1 to 10 (high value: less starch) contents. This is brought about by the reaction of trees to water shortage: with less wate availabel a reduced amount of sugar is used by the tree for fruit and shoot growth. Th higher sugar content at farm C coincided with a lower starch content. However after takin into account the difference in starch content, a statistically significant difference of 1.1 sugar content remained. From the high starch values (low starch content) it can be seen that Jonagold wa harvested very late. This was caused by the slow colouring of the apples in 1995. B. Firmness. At farm C it was shown that a higher starch content at harvest after wate application corresponded with lower firmness (normally a higher starch content occurs wit higher firmness because of less pronounced ripening). The decrease in firmness is probabl related to the large increase in fruit size. At farms B and D, where the effect of the wate application on fruit size is less pronounced, no differences in firmness were found. C. Calcium content. The farms B, C and D also differed in the effects of water on th calcium content of the fruits. At farms B and D the calcium content was lower afte application of water. This usually occurs after an increase in fruit size. However at farr C the calcium content was not affected after water application despite the marked effec on fruit size. This can probably be explained by a reduction of calcium uptake by the root 112 A.R. 1995 Research Station for Fruit Growing cause of extremely dry soil conditions, or by the export of calcium from the fruits, netreatment s did not have statistically significant effects on blush percentage and ground )lour. om these results it can be concluded that water application in the summer only affects nternal) fruit quality when fruit size is affected. The effect on internal fruit quality is fferent when the size of reduction in water availability is small (farms B and D) as jmpared to when there is a bigger reduction (farm C). It may be that the difference in jltivar is also important in this matter (farm C:Elstar; farms B and D: Jonagold). nprovement of the quality of pit and stone fruits through the water nd nutrient supply IP. van der Maas alcium fertigation troduction ne positive relation between high calcium content of fruits and good storability is well nown. A common way to increase the calcium content (in the outer parts of the fruit) is > spray calcium on the fruits. The disadvantages of calcium spraying are, however, that ley are laborious (when calcium has to be sprayed separately from other chemicals) and lat there is increase risk of russetting. A possible alternative to calcium spraying is alcium fertigation. With calcium fertigation the calcium content of the whole fruit may be creased and so the occurrence of bitter pit may be more restricted. Up to now calcium rtigation has required adaption of the fertigation equipment (two fertilizer tanks instead : one). The Scotts company however developed soluble fertilizers containing all important jtrients including calcium (the Agrasol'F-serie). Two of these fertilizers (Agrasol'F 311 8-7-6-14CaO) and Agrasol'F 313 (14-7-14-14CaO)) are compared with the commonly sed fertilizers which do not contain calcium (19-6-6 and 19-6-20) for the effect on the ilcium availability in the soil solution and the calcium uptake by the fruits. squirements for maximum calcium uptake ne uptake of calcium by the roots is probably dependent upon the ratio of calcium to the :her cations in the soil solution (the cation ratio: Ca/(K + Na + Mg + H+ NH4)). The agnitude of the cation ratio required to ensure maximum concentration of calcium in the jits must be determined. In Table 80 an overview is given about the cation ratios in the >il solution beneath trickle points on September 3, 1993 for two soils (a non-calcareous indy soil in Horst and a calcareous clay soil in Numansdorp). On these soils fertigation cperiments with calcium nitrate and 19-6-6 were carried out. On the calcareous clay soil e calcium uptake of the fruits was the same for both treatments. Apparently 1.5, the west cation ratio in the soil solution with 19-6-6 was still sufficient to ensure the same ilcium uptake as with calcium nitrate. The cation ratios in the non-calcareous sandy soil ere lower than for the calcareous clay soil. From fruit analyses it became clear that the ilcium uptake by the fruits was higher for the calcium treatment corresponding with an 113 A.R. 1995 Research Station for Fruit Growini increase in cation ratio in the soil solution in the first twenty centimetres from 0.4 to 0.7 No data is available on cation ratios at increased depths or for other periods. For the nex study however, it was estimated that a cation ratio of 1.0 would ensure maximum calciun uptake by the fruits. Table 80. Measured contents of cations inth e soil solution under trickle points on 3n September 1993 for calcium fertigation experiments in Numansdorp am Horst. Treatment Soil H K Na Mg Ca Cation ratio depth (cm) (milli-equivalenten/litre) Ca/(H+ K-Na- Mg + NH4) Numansdorp Calcium 0-10 0.0 2.2 7.8 4.6 35.5 2.43 Calcium 10-20 0.0 2.0 8.2 4.9 31.3 2.07 19-6-6 0-10 0.0 1.3 8.9 4.5 23.0 1.56 19-6-6 10-20 0.0 1.3 9.1 3.8 19.7 1.40 Horst K + Mg 0-10 0.0 0.9 1.2 0.6 1.35 0.49 K + Mg 10-20 0.0 0.9 1.5 0.6 1.14 0.38 Calcium 0-10 0.0 0.2 1.3 0.4 1.60 0.84 Calcium 10-20 0.0 0.1 1.6 0.4 1.06 0.52 Simulation of the effects of calcium fertigation. With the computer model OCAFE (Optimalisation CAIcium FErtigation; documention preparation) estimates of the effect of calcium fertigation on the chemistry of the so solution and thus the cation ratio, can be made. The cation ratio is linked with calciur uptake by the fruits (see above). For the non-calcareous sandy soil it appeared that from the third fertigation year onward the cation ratio with Agrasol'F 313/14-7-14-14CaO improved so much in comparison wit 19-6-20 that an increase in calcium uptake by the fruits could be expected (in the fifth an final fertigation growing season the cation ratio was 0.4 to 0.5 for Agrasol'F 313 and 0. to 0.3 for 19-6-20). The positive effect of Agrasol'F311 in comparison with 19-6-6 on th cation ratio of the soil solution was not such that calcium uptake by the fruits would hav changed (cation ratios for both fertilizers lay between 0.3 and 0.4 in the fifth growin season). The pH of the top soil with 19-6-6, however, was greatly decreased and the th total amount of calcium was reduced by 18% from the beginning of the simulations (se Table 81; the amount of soil adsorbed calcium was even reduced by 50%). The pH of th 0-5 cm layer was increased with the Agrasol fertilizers; deeper in the soil no effect wa detected. The total amount of calcium was increased by 4%. The pH with 19-6-2 remained stable but the total amount of calcium was decreased by 7%. Based on thes observations the Agrasol fertilizers are preferable for this kind of soil. 114 A.R. 1995 Research Station for Fruit Growing or the calcareous clay soil 19-6-6 had the highest cation ratio after 5 years of fertigation >etween 1.3 and 1.9) in comparison with the other three fertilizers (ratios between 1.1 nd 1.5). Because differences in the cation ratio of the soil solution beneath trickle points nly have effect below 1.0, calcium uptake was probably not affected. Differences in pH rere not found (see Table 81). The total amount of calcium in the soil was reduced by 2 with the Agrasol fertilizers (see Table 81). Fertilizers 19-6-6 and 19-6-20 showed iductions of 5% and 6% respectively (averaged over the rooting depth; in the 0-5 cm yer the reduction was 30%, in the 10-15 cm layer 17% and in the 45-50 cm layer 0%). or this calcareous clay soil no one of the fertilizers is preferable to any other where alcium uptake in the first 5 years is concerned. However the decalcification of the soil can s seen as a negative aspect (destruction of natural soil fertility) and continuation of rtigation may finally lead to reduction of pH and cation ratio. able 81. The calculated pH of the soil solution and the calcium content of the soil under trickle points before and after 5 years of fertigation with non-calcium containing (19-6- 6 en 19-6-20) and calcium-containing fertilizers (Agrasol'F 311/8-7-6-14CaO en Agrasol'F 313/14-7-14-14CaO) in Numansdorp and Horst. Before fertigation After 5 years fertigation **) with (1 January) 19-6-6 19-6-20 'F 311 F 313 orst H 0- 5 cm *) 6.0 5.2 6.0 6.7 6.6 H 25-30 cm 5.6 4.7 5.5 5.6 5.5 alcium content of 0.045 0.037 0.042 0.047 0.047 ie soil (mol/kg soil) umansdorp H 0- 5 cm 8.1 7.6 7.7 7.7 7.7 H 25-30 cm 7.6 7.1 7.2 7.2 7.2 alcium content of 0.71 0.68 0.67 0.70 0.70 ie soil (mol/kg soil) pH of the soil solution ) for pH the average of the growing season; for the calcium content, the value in December of the fifth year. he calculated effects of the fertilizers on the two soils can be explained by one or more f the following aspects: the calcium concentration of the fertilizer (the Agrasol fertilizers contain calcium) the nitrogen concentration and form of the fertilizer; ammonium initially results in increasing calcium concentrations in the soil solution, but after depletion of the calcium buffer it finally results in decreasing calcium concentration and pH; 19-6-6 contains a relatively high amount of ammonium; the nitrogen 115 A.R. 1995 Research Station for Fruit Growin concentration of the fertilizers varies from 14% to 19%. the potassium content of the fertilizer (ranging from 6% to 20% K20) the amount of fertilizer that was used (standard recommendations: 0.6 g/tree/day for F'311 and 19-6-6 and 0.85 g/tree/day for F'313 and 19-6-20) the calcium buffering of the soil (low for the non-calcareous sandy soil and high fc the calcareous clay soil. Water and nutrient requirements of strawberries and berry fruit W.A.G.M. Jansen Water requirement of blueberry In the spring of 1994, two-year-old bushes of the cultivar Bluecrop have been plantée for a trial with various irrigation regimes from planting onward. These regimes were: n water supply and a supply of 0.5, 1.0 and 1.5 times the evaporated water quantit\ Fertilization was given in one or three times during the season. The objects without an water supply, grew very poorly. As a result of the very warm summer almost all th bushes died. The vigour of these bushes was very terse and the leaves were strongl curled and had a yellowish colour. The bushes developed better the higher the amour of water supply (Table 82). Table 82. Harvest data 1995 and growth data 1994 and 1995 water-supply trii Bluecrop blueberry Ferti G/bush Mean fruit Crop health index (*) lization weight (g) autumn '94 autumn '9 No water . 1x 25 1.6 2.5 -- (#) No water . 3x 67 1.6 2.5 6.0 (#) 0.5x evapor. 1x 147 1.7 7.3 7.1 0.5x evapor. 3x 61 1.6 7.0 7.4 1.O x evapor. 1x 106 1.7 7.0 7.7 1.O x evapor. 3x 118 1.7 7.3 7.4 1.5x evapor. 1x 151 1.6 7.1 7.6 1.5x evapor. 3x 113 1.7 7.6 7.7 (*) 1 = very bad, 9 = very good (#) (almost) all bushes died 116 A.R. 1995 Research Station for Fruit Growing ptimization fertilization - recommendation basis for strawberry and ush and cane fruit I.A.GM. Jansen ptimization fertilization blueberry the spring of 1994, two-year-old bushes of the blueberry cultivar Bluecrop were anted and from the year of planting fertigated with a given amount of nitrogen jmbined with a high and/or a low dosage of phosphate and potassium. The given trogen level was based on earlier trials in Horst. An object with organic manure was eluded in the trial. All fertilization treatments will be carried out annually. The rtilizers were applied three times during the season; the organic manure once. The jshes of all objects grew well in the first year, except those with the highest concen- ation of fertilizers. Probably, salt concentrations were too high for the one-year-old jshes. Some bushes showed some damage from the organic manure (Table 83), cause the manure was applied too close to the stems. able 80. Harvest data 1995 and growth data 1994 and 1995 fertilizer trial Bluecrop blueberry G/bush Mean fruit Crop health index (*) weight (g) autumn '94 autumn '95 ,-p, -K 462 1.9 7.6 7.4 , -p, LK 420 1.8 7.4 7.2 ,-p, HK 496 1.8 7.6 7.1 , LP, -K 520 1.8 7.6 7.3 , LP, LK 448 1.8 7.8 7.9 , LP, HK 259 1.8 8.0 7.8 , HP -K 450 1.7 8.1 8.1 , HP LK 440 1.7 8.1 7.6 , HP HK 292 1.7 7.1 7.4 M,HF' , HK 375 1.8 6.9 7.2 rgan sehe mest 464 1.8 7.3 5.3 1 = very bad, 9 = very good = n itrogen K = potass ium H = high dose = phosphate L = low dose - = no dose 117 A.R. 1995 Research Station for Fruit Growin Crop Protection Phytopathology and Weed Control Biology and control of secondary or sporadic disease in fruit crops H.A. Th. van der Scheer and W.A.G.M. Jansen European canker In the spring of 1995, European canker was a serious problem in many apple orchard: Also on pear the disease was manifest. In the autumn of 1994, extensive infection < the leaf marks by Nectria galligena must have occurred. At that time, the conditior were very favourable for infection by the pathogen: it was very wet. That made tl" grass strips impassible. Thus, many growers were unable to apply fungicides to the trees. On the other hand, spraying in the leaf drop period had not been customary fc many years, as from the beginning of the eighties, European canker had not been problem. in the Betuwe region the disease occurred more seriously than elsewhere in Tr Netherlands. Presumably the disease could be more damaging here, because February 1995 the trees were weakened due to root death caused by a high level ( subsoil water. That level arose as a consequence of the prolonged high level of tr water in the big rivers in the centre of The Netherlands. Root rot in pear In 1994, the presence of Roesleria pallida and Rosellinia necatrix was demonstrated dead roots of poorly-growing pear trees and in dead roots of quince in stool bed Before 1994, the latter pathogen was hardly seen in orchards and fruit tree nurseries The Netherlands. Both pathogens do like warmer summers, Rosellinia even more the Roesleria. Such summers have prevailed in the last five years. So far, in orchards, only the small greyish apothecia of Roesleria pallida have bee observed on dead roots of diseased pear trees. However, in the summer of 1995 fi the first time the white mycelium of Rosellinia necatrix was found abundantly arour the roots of poorly-growing young pear trees (Conference on Quince Adams) in i orchard near Kruiningen. The young pear trees were planted in soil where in 1994 app trees over forty years old were grubbed. Young pear trees from the same consignme which were planted elsewhere, did not show disease symptoms. It is assumed that tl pathogen occurred on the root remains of the old apple trees. In the spring of 1994, a number of young pear trees which displayed apothecia i Roesleria pallida on their roots, were treated with Topsin M sp., or with Sportak or we left untreated before planting in the orchard. As in 1994, in 1995 no growth different between the trees were recorded. 118 A.R. 1995 Research Station for Fruit Growing ï a second trial the growth of trees with Roesleria pallida apothecia on their roots, was ss good than the growth of visibly healthy trees from the same consignment, owever, in 1994, the first year after planting, the growth differences were more :riking. ruit rot on blueberry p to 1994, fruit rot on blueberry, caused by Colletotrichum acutatum, was problematic nly in a few plantations. However in 1994, the disease occurred seriously in many antations. Therefore in 1995, the effectiveness of applying sprays with 0.15% Captan 3% sp and 0.25% Eupareen spk with a weekly interval was tested. In The Nether- nds, both fungicides are approved for control of fruit rot in blueberry and application allowed up to 10 and 21 days respectively before picking. Also timing of spraying uring the season (a. before blossoming, b. from beginning of blossoming until picking, id c. after picking) was the subject of research. The results are shown in Table 84. he fungicide applications were most effective in the period from beginning of blosso- ling until picking. Both fungicides did not differ significantly in effectiveness. able 84. Control of Colletotrichum fruit rot on blueberry pray applications in the period % rotted berries efore bloom bloom-picking after picking ntreated untreated untreated 20.0 b itreated Captan 83% sp untreated 3.4a ntreated Eupareen spk untreated 6.2 a jpareen spk untreated Eupareen spk 14.8 b jpareen spk Captan 83% sp Eupareen spk 3.8 a jpareen spk Eupareen spk Eupareen spk 5.5 a alues in one column with the same letter(s) do not differ significantly (P= 0.05). iology and control of apple scab .A. Th. van der Scheer evelopment in spring ne ripening of pseudothecia of Venturia inaequalis in leaves of Elstar, Jonagold and ista Bella was investigated. Almost weekly in the period from 16 February to 6 July ie developmental stage of ten pseudo-thecia per apple cultivar was determined. The assification of the stages is with a slight modification, borrowed from Jeger et al. in nnals of applied Biology 100(1982):91-98. At the same time the percentage of ripe oospores per pseudothecium was determined. 119 A.R. 1995 Research Station for Fruit Growin In 1995, the first ripe ascospores were observed on 15th February. As in the previoi year pseudothecia in leaves of Vista Bella ripened faster than in leaves of Elstar an Jonagold. The largest number of ripe asco-spores was recorded in the first half of Apri At the beginning of July ascospores no longer discharged from the pseudothecia. TT ascospores finished discharging at exactly the same time in the leaves of all three app cultivars. Testing fungicides In 1995 a number of fungicides were tested for control of scab. Therefore, in the peric from 14 March to 27 June mature trees of the variety Jonagold were sprayed at week intervals. Leaves and fruit of untreated trees became heavily attacked. All fungicic treatments gave good control of leaf scab. However, scab on fruit was less w« controlled by the anilino-pyrimidine fungicides Scala and PAF-95-001. The production varied greatly between the trial trees due to insect damage. Therefon no significant differences could be observed between the scab control treatment: However, the average weight of apples from untreated trees tended to be lower the those from treated ones. Spraying with Captan 83% sp and with PAF-95-001 résulte in a visible residue on the fruit. Resistance to DMI fungicides In 1994, it was demonstrated that conidia of Venturia inaequalis had become les sensitive to DMI fungicides. In 1995, it was established that ascospores also were les sensitive to the DMI fungicides Baycor and Score. The ascospores originated froi leaves of 1 5 different orchards. Leaf drop acceleration At the beginning of the leaf drop period in the autumn of 1994 Ethrel-A (in a concei tration of 0.1% and 0.2%) and Defoliant (in a concentration of 2% and 4%) wei applied to Elstar and Jonagold trees to accelerate their leaf drop. As directed, spreader (0.1%Tween-20 ) was added to the Defoliant spray liquid. Acceleration of tr leaf drop can have advantages in terms of control of scab and European canker. Bol applicants did accelerate the leaf drop markedly. Ethrel-A was even more effective thé Defoliant. Differences in effect between concentrations were small. Also a secor application two weeks later hardly improved the effect of the one application. Negativ effects on blooming in 1995 were not observed. Biological control of diseases in fruit crops H.A. Th. van der Scheer and CA. van Zuidam Powdery mildew on gooseberry In the experimental orchard at Geldermalsen the effect of Milsana was tested c 120 A.R. 1995 Research Station for Fruit Growing owdery mildew on gooseberry, caused by Sphaerotheca mors-uvae. Milsana is a plant xtract and should make plants less susceptible to diseases. The product was sprayed t weekly intervals on potted plants of the cultivar Whinham's Industry in a plastic unnel. However, spraying with 2% Milsana was not effective. Good control of the iowdery mildew was achieved by applying fungicide sprays, and using 0.04% Rubigan lb as a control. 'opulation dynamics of Pratylenchus penetrans in fruit crops V.A.GM. Jansen lomparison of various preceding crops for the control of replant disease caused by the ematode Pratylenchus penetrans. \ number of plants of the composite family are effective against the lesion nematode 'raty/enchus penetrans. In the spring of 1990, the following crops have been planted s preceding crops on a plot infected by Pratylenchus penetrans: Tagetes patula, 'chinops ritro, Eriophyllum ceaspitosum (=lanatum), Gaillardia hybride "Burgundy" and lenenium hybride "Moerheim Beauty". These crops were compared with a fallow bject. Half of the preceding crops were planted in a chemically disinfected soil, the ther half in a not treated soil infected with nematodes. On both the infected plots and he disinfected plots, half, the preceding crops were ploughed in before the trees were lanted. On the other half of the vegetation was maintained. In the spring of 1991, -ees of the cultivars Elstar and Jonagold on M.9 were planted. Table 85 summarizes ne treatments involved. i 1991, in the non-disinfected plots, only Tagetes patula gave a reliable control of 'ratylenchus penetrans. In 1992, Tagetes patula, Eriophyllum, and Helenium seemed to ave a suppressive effect on the nematodes. Disinfecting the soil and ploughing in the lants gave more growth in all objects compared to the fallow objects. The non- isinfected objects gave the same result (but everything on a lower level than in the isinfected objects). No disinfection combined with a preceding crop gave a similar or ven stronger growth than the combination disinfection and fallow, laintaining the preceding crop under the fruit trees caused such a competition , that ~\e trees showed very poor growth (in spite of fertigation). ifter the preceding crop had been ploughed in, Tagetes, Echinops, Eriophyllum and Gaillardia gave a higher production per tree than the fallow object. Gaillardia, although erennial, did not come back after the winter. Echinops did come back in spite of erbicide application. Sowing of Eriophyllum turned out to be an unsatisfactory method Dr it covered the soil insufficiently, so that (in spite of weed control) too much weed eveloped. For a good control of Pratylenchus penetrans with a preceding crop, the ccurrence of weeds is unacceptable, for these act as host plants for nematodes. Some roduction data are given in Table 85. 121 A.R. 1995 Research Station for Fruit Growin Table 85. Crop data 1992 till 1994 trial preceding crop apple Preceding crop Kg/tree Fruit weight (g) disinfected not-disinfected disinfected not-disinfecte no crop under the trees Elstar Fallow 52 39 175 153 Tagetes 53 47 172 172 Echinops 46 44 179 167 Eriophyllum 59 48 180 178 Gaillardia 50 46 177 166 Helenium 48 41 166 178 with crop under the trees till spring 1992 Fallow 43 34 176 154 Tagetes 48 48 174 174 Echinops 42 36 177 167 Eriophyllum 43 35 177 178 Gaillardia 53 46 174 168 Helenium 32 30 175 168 no crops under the trees Jonagold Fallow 56 50 230 238 Tagetes 64 47 245 253 Echinops 65 62 242 247 Eriophyllum 72 70 256 254 Gaillardia 66 58 240 236 Helenium 67 59 245 239 with crop under the trees till spring 1992 Fallow 61 50 256 231 Tagetes 63 60 251 246 Echinops 59 61 257 248 Eriophyllum 63 55 249 250 Gaillardia 73 60 247 242 Helenium 59 49 225 249 Optimization of alternatives for chemical soil disinfection The sowing of the African marigold, Tagetes patula, offers good possibilities as a alternative for chemical soil disinfection. A plant hole treatment with potting soil i combination with fertigation may also improve the growth of trees in soils infected wil the nematode Pratylenchus penetrans. In the spring of 1993 a trial was started 1 optimize the growth of trees, planted in an infected soil. Half of the plot was nc disinfected, the other half was chemically disinfected. On both plots, Tagetes as preceding crop was compared to fallow objects, and as sub-treatments potting soil an fertigation were included. The apple cultivar involved was Golden Delicious on M. rootstock. Table 86 pictures the treatments involved. All disinfected objects gave better growth and production than the non-disinfecte 122 A.R. 1995 Research Station for Fruit Growing 'bjects (Table 86). Addition of potting soil and fertigation gave an improvement of rowth and production in both the disinfected and the non-disinfected objects. There vas only a small difference in vigour between the fallow objects and Tagetes, but the iroduction of the Tagetes objects was higher than the production of the fallow objects, addition of potting soil and fertigation to trees in infected soil, gave after two producti- m years a similar or even higher production than the trees planted in disinfected soil vithout fertigation and potting soil. However after sampling the soil on the presence 'raty/enchus penetrans, these nematodes turned out not to be present. Sampling on ungis showed that among several species, Pythium was frequently present. So the lifferences in growth and production between the various treatments might be xplained by their affect on Pythium. If this is true, specific replant disease was ivolved. Former trials showed that replant disease caused by nematodes can not be ufficiently controlled by a plant hole treatment, but it does have an effect, on replant lisease caused by fungis. able 86. Growth and harvest data Tagetes trial with Golden Delicious "reatment Average Increase Kg/tree Fruit is- prece fer pott shoot Igth trunk 1994 + weight ifected ding tiga soil /tree (cm) circumf.(cm) 1995 (g) crop tion autumn '93 spring '93- '94'95 autumn '95 15.6 4.2 14.2 161 18.3 5.2 18.6 148 +1 ) 16.5 4.7 16. 156 +1 ) 20.9 5.8 21. 154 18.4 5.4 17.3 160 27.1 6.4 25.6 154 18.2 5.2 19.2 157 M + 26.8 6.3 24.4 150 Tagetes ontrol of nematodes with bacteria i the spring of 1994, a trial was carried out to test the effect of a bacterium preparati- n against replant disease caused by free living root nematodes. This preparation onsists of a manure extract with specific bacteria that would have an effect against ie nematode Pratylenchus penetrans. The bacterium preparation was applied before lanting of the fruit trees, when the soil temperature was above the required 8°C. The eatment did not have any suppressing effect on the number of nematodes. Not jprisingly all trees had the same growth level in the planting year. (Table 87). 123 A.R. 1995 Research Station for Fruit Growir Table 87 Number of Pratylenchus penetrans nematodes per 100 ml soil ar growth data in nematode-control trial with appli a Nematodes/100 ml soil Trunk Increase circumf.(cm) trunk 8 April 1994 20 May 1994 spring '! 35 circumf.(cm) (initial situation) (final situation) 1994 . Overallc isinfection 0.0 •') 6.4 1.4 Non-disiiifecte c + Bacteria preparation 12.5 11.7 6.1 1.1 Non-disi nfectec 2.9 --*) 6.2 1.2 *) not sampled Table 88 Crop and growth data in soil-disinfection trial Treatment Trunk In Kg/tree Fruit weight(( cir- crease disinfec Nema ferti- pott. cumf. trunk 1994 1990 1994 199 ted non gation soil (cm) circumlf . - - spring spring 1994 199 1994 1991 - spr.'95 . . 11.5 6.6 7.3 19.0 191 175 - - +* ) - 11.6 6.7 9.4 24.6 183 178 - - + + 12.8 7.8 13.1 34.3 177 170 + - _ _ 14.7 9.7 17.5 40.7 174 181 + - +* ) - 14.2 9.2 17.3 35.3 173 189 + - + + 14.9 10.1 19.3 45.9 166 172 - + - - 10.7 5.8 8.1 17.6 169 168 - + + - 11.9 7.0 15.6 31.4 154 161 - + + + 11.6 6.9 11.5 27.5 166 160 + + _ _ 14.3 9.6 20.1 40.2 160 181 + + + - 14.0 9.0 21.7 41.6 152 171 + + + + 14.5 9.3 22.5 49.0 150 167 *) relatively many trees died (cause unknown) 124 A.R. 1995 Research Station for Fruit Growing Iternatives for chemical soil disinfection. i the autumn of 1990, a trial was started in order to examine combinations of the 'eceding crop Tagetes 'Nemanon', fertigation and potting soil in the plant hole as ternatives for chemical soil disinfection against apple replant disease caused by the smatode Pratylenchus penetrans. In the spring of 1990 in half of the experimental field ie vigorous Tagetes cultivar 'Nemanon' was sown and the other half remained fallow, the autumn of 1990, half of each plot was chemically disinfected with Metam atrium. In the spring of 1991, Golden Delicious trees on M.9 rootstocks were planted i all plots. The trees were either planted in a hole with potting soil or without such a 3at mixture. Sub-treatments with or without fertigation were included (Table 88). agetes 'Nemanon' did not have any effect on the growth of the trees, but disinfection d. Nemanon did not have a nematode suppressing effect. Where no disinfection was arried out, growth was stimulated by the combination of potting soil and fertigation. owever both in growth and in production the combination of fertigation and potting 3il on non-disinfected soil did not equal the effect of chemical soil disinfection (Table 8). The trees of the plots in which Nemanon had been the preceding crop, looked lore vital than those in the fallow plots. This difference may be explained by the jantity of organic matter brought into the soil as a result of the ploughing in of the emanon plants. rigin of planting material and soil treatment the spring of 1992, trees of Elstar and Cox's Orange Pippin were planted. Raised ther on a plot infected with nematodes {Pratylenchus penetrans), or a non-infected able 89. Harvest data of 1993 and 1994 in plant material soil treatment trial with apple eatment Cox's O.P. Elstar ant potting kg/tree fruit kg/tree fruit aterial soil weight weight (g) (gj isinfected soil fected + 10.5 165 23.3 157 fected - 8.8 164 21.1 156 )n-infected + 11.3 159 25.8 151 >n-infected - 12.0 158 22.6 165 Dn-disinfected soil fected + 6.9 137 11.2 141 fected - 4.3 125 8.1 143 >n-infected + 6.4 125 10.3 145 >n-infected - 5.3 121 8.7 143 125 A.R. 1995 Research Station for Fruit Growini plot. Both groups of trees were either planted on a plot infected with nematodes or on chemically disinfected plot. As sub-treatments filling the plant hole with potting soil am fertigation were included (Table 89). Trees on disinfected soil grew more vigorousl' than on a non-disinfected soil and in both cases the use of potting soil in the plantini hole favoured growth. Trees from a non-infected nursery situation grew better thai those from an infected situation, but only on disinfected plots. So by combining health trees and a disinfected soil a good start of the orchard can be achieved. The growtl differences expressed in clear differences in production (Table 86). Especially in th non-disinfected soil, the use of potting soil increased growth. The trial shows that potting soil in the planting hole and fertigation are no goo alternative for chemical soil desinfection. Testing of various rootstocks for their susceptibility to nematodes In the spring of 1994, a number of new rootstocks was planted in disinfected and nor disinfected soil in order to determine their susceptibility for the root lesion nematod Pratylenchus penetrans. In the autumn of 1995, the rootstocks were budded in sit with Cox's Orange Pippin and Golden Delicious and were planted both in infected and i chemically disinfected soil. The number of nematodes are given in Table 90. In 1994, all unbudded rootstocks grew more vigorously on disinfected soil as compare to non-disinfected soil (Table 91). Jork 9 was the most vigorous grower on both nor disinfected and disinfected soil. In the non-disinfected soil, Jork 9 showed a growt level comparable to M.9 in disinfected soil. Except for Jork 9 and in one case P 346, a Table 90. Number of Pratylenchus penetrans per 100 ml soil Spring 1994 Autumn 1994 Cox's O.P. Golden D. Cox's O.P. Golden 1. overall disinfected 0 0 0 0 2. non-disinfected 127 93 5 30 rootstocks in non-disinfected soil, grew less than M.9 in disinfected soil. At the end c 1995 all rootstocks in non-disinfected soil had a lower growth level than that of M.9 i disinfected soil. So, it is doubtful whether a rootstock can be found that overcomes th damaging effects of the nematodes involved. Ridge culture with potting soil against nematodes In the spring of 1994, a trial was planted with so-called 3-K Elstar trees. The trees wet planted in ridges or normally to see whether this could be an alternative for chemie soil disinfection. A ridge culture might be able to reduce the infestation by nematode from the subsoil. The ridges were made of a mixture of non-infected soil and pottin soil. Half of the ridges were covered with mushroom compost the other half remaine uncovered. For the treatments see Table 93. The nematode population at the start c 126 A.R. 1995 Research Station for Fruit Growing ie trial can be found in Table 92. ne trees planted in disinfected soil gave most growth and the highest production. All :her treatments were about equal and did not satisfy with regard to growth and oduction (Table 93). Covering the ridge with mushroom compost had a slight positive feet, but also insufficient. Thus planting in ridges does not seem to be a useful ternative for chemical soil disinfection. able 91. Growth 1994 and 1995 in apple rootstock trial bjecten Average shoot length (cm) Increase trunk circumference (cm) autumn 1994 spring 1994 - autumn 1995 Cox's O.P. Golden Delicious Cox's O.P. Golden Delicious + - + - + - + - .9 T.337 31.9 15.2 28.5 17.3 4.4 1.2 3.6 1.2 .9 FL.56 36.3 18.1 37.9 19.9 4.7 1.5 4.0 2.1 .9 Cepiland 22.8 16.2 29.8 17.7 2.8 1.5 4.0 1.5 .26 26.6 16.0 17.1 20.9 4.0 1.5 3.6 1.8 .27 20.8 17.5 32.2 11.4 2.6 1.0 3.6 0.8 16 22.8 20.3 27.9 21.5 2.6 0.9 4.2 1.3 22 32.7 25.1 37.9 20.0 3.8 1.7 4.0 1.6 2 60.4 24.6 54.5 23.6 5.4 1.7 4.2 1.4 >rk 9 60.4 31.2 61.9 32.9 3.5 1.2 4.2 1.6 9 37.4 24.2 34.1 20.6 3.5 1.6 3.3 1.2 ) 346 65.4 30.4 49.4 20.8 3.6 0.9 3.9 0.8 ) 508 38.8 25.7 47.9 16.2 5.1 1.7 4.6 1.3 + = disinfected; - = non-disinfected ible 92. Number of nematodes per 100 ml soil Dject Autumn 1993 Autumn 1994 serail disinfection 5.0 0.0 )n-disinfected overall + potting soil 27.5 5.0 3n-disinfected in ridge + potting soil 93.8 0.0* )n-disinfected in ridge + potting soil + 38.8 0.0' ushroom compost sampled only in'the ridge 127 A.R. 1995 Research Station for Fruit Growini Table 93. Growth 1994 and production 1995 in a ridge-culture trial with Elstar Overall Ridge Potting Mushroom Growth/ Increase Kg/tree Average dis- soil compost tree (m) trunk fruit fected cover 1994 circumf. weight (cm)* 8.0 5.4 8.0 175 + - + - 2.7 2.4 3.9 140 + + + - 3.0 2.1 3.3 149 + + + + 3.7 2.8 4.5 158 after two growth years Strip disinfection compared to overall disinfection In the autumn of 1993. a trial was started in which overall disinfection was compare to tree strip disinfection. With the latter method, the quantity of soil disinfectant i considerably reduced. In the autumn of 1993, a plot infected with the nematod Pratylenchus penetrans was either completely disinfected, or strip wise or left untreé ted. In the spring of 1994, Cox's Orange Pippin trees on M.9 rootstocks were planted. In 1994, no differences in growth were observed between overall disinfection or stri disinfection. The trees in non-disinfected soil fell already into considerable arrears. I 1995, there were no differences in production between the overall disinfected and stri disinfected objects. The production of the trees in non-disinfected soil, was only half c the production of the trees planted in disinfected soil (Table 94). Table 94. Results disinfection trial with Cox's Orange Pippin Disinfection Growth/ Increase Kg/tree Average Nematodes/100 ml tree (m) trunk fruit soil 1994 circumf. weight autumn (cm)* (g) 1993** 1994 Not 2.0 1.8 4.5 100 65.8 45.0 Overall 6.8 4.9 8.1 187 0.0 0.0 Tree strip 6.6 4.6 9.0 176 0.0 5.0 after two growth years; ** sampled after disinfection 128 A.R. 1995 Research Station for Fruit Growing 'ntomology and Biological Control 'esting of insecticides, fungicides and bactericides in fruit growing . Woets ests of three potential aphicides ,t Wilhelminadorp three potential aphicides were tested against the rosy leaf-curling phid Dysaphis devecta. Two of them were from the new insecticidal group of the hloronicotinyles. The third compound was a commercial formulation of a neemtree- eeds extract, and was applied as four treatments: two treatments using different bncentrations and two further treatments using these same concentrations but issolved in rape oil before water was added as a spraying liquid. The agents were prayed on Jonagold shortly after blossoming, when the leaf-galls caused by D. devecta /ere well developed. Before spraying, and 2 and 13 days after spraying the living ahids were counted in 10 colonies per plot. he two chloronicotinyles proved to be as effective as the standard treatment of irimicarb. The 4 neemtree-seed applications had no significant effect on the aphid umbers, although the two treatments of the seed extract in rape oil gave lower umbers of living aphids than did the neem extract itself. here were, no residues visible on leaves and fruits nor scorch from the spraying, till arvest. t Geldermalsen the same agents were sprayed against the rosy apple-aphid Dysaphis lantag/nea before bloom. One month after blossoming the numbers of shoots with i/ing aphids were counted. The chloronicotinyles and the higher neemseed extract oncentration in rape oil worked as effectively as the standard treatment pirimicarb. The iree other neemseed treatments did not differ significantly from the untreated. he two chloronicotinyles were also sprayed shortly after bloom. The numbers of loots with living aphids were counted one month after bloom, at the same time as the eatments mentioned before. The numbers of infested shoots in the post-blossom eatments were as low as those in the pre-blossom treatments and the pre-blossom Dntrol. o residues were seen on leaves and fruits, nor any negative effect on leaves, fruits nd general growth pattern. i summer an infestation of the fruit tree leafhopper Edwardsiana rosae occurred. In the lots with chloronicotinyles the infestation level was suppressed. Both damage to the aves and the number of coated fruits were decreased. ests of insecticides against the mullein bug ince 1993 the mullein bug Campylomma verbasci has been a new pest on apple in urope. In two trials at Horst some common spring insecticides were applied, i.e. the Dmmon bug insecticides dimethoaat and propoxur and the honey-bee-safe phosalone. he new compound imidacloprid (Admire) from the group of chloronicotinyles was isted also. Propoxur and dimethoaat had a significantly decreasing effect on the 129 A.R. 1995 Research Station for Fruit Growin numbers of bug larvae one month after blossom. Phosalone and imidacloprid had n such effect. At harvest the numbers of stung fruits were counted, but there were n reliable differences between the four chemical treatments and the untreated, althoug both propoxur and dimethoaat treatments had lower numbers of stung fruits than tr other treatments. Integrated control of pests on top fruits J. Woets Integrated control of pests on apple Since 1 945 the summer fruit tortrix Adoxophyes orana has been the dominant caterpi lar pest in apple and pear in the Netherlands. For some years there have been indica! ons that other leaf-roller species may play a part in the total leaf-roller damage estimi ted at harvest. There has been a low presence of summer fruit tortrix caterpillar: despite the usual damage levels, and a high moth catch of the other leaf-rollers i pheromone traps. These other potential leaf-roller pests are the dark fruit tree tortri Pandemis heparana, the fruit tree tortrix Archips podana and the bud moth Spilonoi ocellana. The caterpillars of the four above-mentioned species damage the fruits in an almo; identical way. So it is difficult to establish a clear relationship between the number c caterpillars (in spring and autumn) or moths (in traps) of a certain species in the orchar and the damage occurring during harvest. Ideal experimental situations would be foun in orchards where only one of the four species occurred. Then the relationship betwee numbers of caterpillars or moths and the damage level could be estimated per specie and probably damage thresholds could be determined. Damage thresholds could be a important basis for decisions on (chemical) control, leading to careful and economi use, and also the protection of the environment and the avoidance of resistanc problems. Pest control advisers have been using damage thresholds for the codling moth Cydi pomonella for about the past eight years. Several situations occur annually in commerc al orchards which do not fit into the actual knowledge on thresholds and damage level; New data could be helpful to establish a more precise damage threshold for apples. As in 1993 and 1994 observations were made in co-operation with colleagues of th Institute for Phytopathological Research IPO and the Dutch Agricultural Service DLV. During 1995 data was collected from 12 Jonagold-plots of 1 ha distributed over th country. 10 of those were the same as in previous years. Males were counted weekl in two sex pheromone traps per plot and the numbers of fruits damaged by leaf-roller and codling moth were determined at harvest. After harvest, caterpillars were collecte on the leaves. In 7 out of the 12 plots no chemicals were applied for control of leaf- rollers. In 5 plot fenoxycarb was applied before or after bloom against leaf-rollers (2 before bloor against summer fruit tortrix and 3 after bloom against other leaf-rollers). No spraying for codling moth control were done. The results of this year differ very much from those of the two preceding years. In 130 A.R. 1995 Research Station for Fruit Growing able 95. Average moth catches (with s.d.) of leaf-rollers and codling moth in two pheromone traps per plot and average numbers of damaged fruits, also as a percentage, in the 12 plots of Jonagold in 1995. Catches Damage Number Percentage av. mm. max. av. mm. max av. mm. max. \doxophyes oran a 55 0 232 'andemis heparana 28 3 83 \rchips podana 115 25 252 49 0 86 2.4 0 41 'pilonota ocellana 121 41 293 'ydia pomonella 79 4 258 44 0 433 2.2 0 21 lots less than 50 A. orana were caught over the year and also low numbers of P. eparana (see table). Relatively high numbers of A. podana (>100) and S. ocellana >100) were trapped in 6 out of the 12 plots (in two traps), mainly in the Flevopolders, etween the main rivers and in the south-east. They are at least partly responsible for ie leaf- roller damage on the fruits (1-4%). The numbers of caterpillars in autumn were 0 low that they did not provide information. 1 2 plots with higher numbers of codling moth there was much damage. In the 10 lots with low damage the caught male numbers varied very much. Statistical analysis as yet to be done. arnation leaf-roller l the south-western part of the Netherlands (in Kapelle) the carnation leaf-roller 'acoecimorpha pronubana was discovered as an established Mediterranean leaf-roller pecies. ex pheromone traps with the RAK dispenser (BASF) were distributed over 12 Jonagold lots in the country. In 3 of those, males were caught in low numbers (1-6) over the ear. These figures indicate that the caterpillars of this species have already established nthin 1 km distance. aterpillars were found on several new host plants in private gardens, including apple nd pear. This is the first reported case in the Netherlands. amage by bugs uring analysis of the crop of the 12 Jonagold plots for leaf-roller research we estima- ;d all types of insect damage. So we counted 3.4% bug- stung fruits at Horst, ecause of the sampling during bloom we know for sure that this was done by the lullein bug Campylomma verbasci. From the plot at Bunnik we estimated 5.8% stung onagold fruits; according to the beating samples directly after blossom this was done y the black apple capsid Atractotomus mali. This is the first reported case of damage y this species. In the plot at Wilhelminadorp many A. mali larvae were found in ysaphis devecta colonies, but we could only find less than 0.1 % bug-stung fruits, that 131 A.R. 1995 Research Station for Fruit Growin the common green capsid nymphs which were present were mainly blamed for. Biological control of pests on strawberry and soft fruits J. Woets Guest worker Robert Sekrecki from the Polish National Fruit Research Institute < Skierniewice did a literature search and compiled his own observations on the damag by the Western flower thrips Frankliniella occidentalis on strawberry. He found syrnj toms on flowers, at different stages of fruits, and on leaves. Feeding by thrips on flowers may cause problems with pollination, necrotic flecking an finally, disformed fruits. Necroses are visible mainly on pistils and stamens but somet mes on petals also; with large numbers of pest, blossoms may also fall off. Most ofte adults and older larval stages are present on these organs. It was clear that immature fruits of strawberry were suitable for larvae. On young früh first symptoms are recognized as bronzing of the seeds. Some of the seeds are mor prominent, others die. Continued feeding on the surface between the seeds induce goldening of the fruit skin. As the fruit ripens this symptom becomes less eviden Every scar on the skin of a mature fruit is an excellent place for sucking. Thrips feedin in this stage cause the fruits to become soft. Symptoms on the leaves are very typical: silver, unregular spots between the nerve and excreted specks of black frass. Development of farming systems for integrated fruit growing A.M.E. Schenk, C. Dekker, H. Veijer Aim The aim of the Integrated Fruit Growing project is to develop an economic production c apple, minimizing the undesirable side effects of chemical pesticides and fertilizers o human health and the environment. Materials and methods Farming systems research for current apple cultivars Until 1994, the experiment was located in two experimental gardens, Numansdorp an Zeewolde. In 1995 Numansdorp was stopped. Three farming systems are comparée Treatment 1 (standard), treatment 2 (integrated) and treatment 3 (minimum). In sprin 1990, eight cultivars were planted in single rows (3 x 1.25 m) with each cultivar in tw to four rows. The widely-grown apple cultivars were Elstar, Jonagold, Alkmene, Cox': Discovery, Rode Boskoop and the scab and mildew-resistant hybrids from the CPR (Ecolette, 78039-27). Each treatment comprised 0.5 ha. In treatment 1, all treatmem and techniques used, were approved in accordance with the guidelines for Integrate Fruit Growing. Predatory mites were introduced and selective pesticides were used. I 132 A.R. 1995 Research Station for Fruit Growing eatment 2 lower dosages of pesticides were used. Whenever possible only products lowed in groundwater protection areas were sprayed. Herbicide use was decreased by ducing the weed-free strip. Used insecticides were safe for predatory mites and also >r other predators. In treatment 3, a minimum use of pesticides was achieved by placing them with biological and mechanical techniques. 3sults in 1995 'ites: Predatory mite (Typhlodromus pyri), rust mite (Acutusschlechtendali) and red )ider mite (Panonychus ulmi) biological balance has been established with the following characteristics: no spider ites, few rust mites and few predatory mites (Figures 15, 16 and 17). osy appleaphid (Dysaphis plantaginea) rst adults of rosy apple aphid were found on 29th April. Treatments 1 and 2 were eated with 30 g/ha Pirimor. Treatment 3 was treated with 20 g/ha Pirimor. In June sy apple aphid could still be found and damage at harvest was recorded. See Table 3. taf-roilers (Torticidae) treatment 1 no control treatment against leaf-rollers and codling moth was done, hile the threshold level was not reached. (Table 97). In treatments 2 and 3 mating sruption has been used since 1990 as a control method for leaf-rollers. At harvest up 4.5% damage by leaf-rollers was recorded. spider mite rust mite pred. mite ouu CM E o - O 400 to CO 3 300 - CO > OB 200 JD O y ç0 CD 100 n E D C L'\ ~~i"' -Li i i rii 5/91 6/917/91 8/91 5/92 6/92 7/92 8/92 9/92 7/93 8/93 9/93 6/94 7/94 8/94 5/95 6/95 7/95 8/95 time gure 15. Mite population in treatment 1 in 1991-1995 133 A.R. 1995 Research Station for Fruit Growir spider mite rust mite pred. mite 500 cv E o O 400 10 5 300 m (U J 200 O & 100 -Q E D C O J L J I I L J L J I 5/91 6/917/91 8/91 5/92 6/92 7/92 8/92 9/92 7/93 8/93 9/93 6/94 7/94 8/94 5/95 6/95 7/95 8/ time Figure 16. Mite population in treatment 2 in 1991-1995 spider mite rust mite pred. mite 500 E u O 400 3 300 (/) Q) S 200 O ID fe 100 E D C 0 J L 5/91 6/91 7/9 1 8/9 1 5/92 6/92 7/92 8/92 9/92 7/93 8/93 9/93 6/94 7/94 8/94 5/95 6/95 7/95 8/ time Figure 17. Mite population in treatment 3 in 1991-1995 134 A.R. 1995 Research Station for Fruit Growing able 96. Infestation of rosy apple aphid in June and damage at harvest in 1995 reatment Infestation in June in % Damage in harvest in % of the kg-production 0 0.2 11 0.6 22 1.1 able 97. Control measurement and damage of leafrollers and codling moth in 1995 'eatment Control measurement Damage at harvest in % of the kg-production Blr Frm Blr Frm 1,8 0 RAK 3+4 RAK 3+4 0,4 0 RAK 3+ 4 RAK 3+ 4 4,5 0 îble 98. Control measurement and damage by Ortosia sp. in 1995 'eatment Control measurement Damage at harvest in % of the kg- production Zolone 0.2 Dipel 2.7 3.2 rthosia sp., Erannis defoliaria, Operophtera brumata ie threshold level of two caterpillars per 100 clusters was not reached in 1994 (Table 3). Operophtera reached the threshold level on 11th April. irwig (Forficu/a auricu/aria) became clear that the distribution of earwigs was very variable throughout the area, some trees, one hundred earwigs could be found, but in some neighbouring trees ily a few earwigs could be found. In 1995 the population peak of earwigs was ached in June-July. 135 A.R. 1995 Research Station for Fruit Growir Common green capsid (Lygus pabulinus) Common green capsid was found in all the treatments. In treatment 3 no contr measurements have been done and damage reached 1.1% of the total harvest. (Tab 99). Table 99. Control measurement and damage by the common green capsid in 199 Treatment Control measurement Damage at harvest in % of the kg- production 1 Imidacloprid 0.2 2 Undeen 0.4 3 1.1 Table 100. Percentage of scab-infected long shoots in August 1995 and percenta« of scab-infected kg fruits at harvest 1995 for Jonagold Treatment Shoots Damage at harvest in % kg-production 1 0.0 0 2 0.0 0 3 1.3 0 Scab (Venturis inaequalis) and powdery mildew (Podosphaera leucotricha) Scab was controlled by a preventive Captan scheme, combined with the curath treatment of Score in case of severe infection. Mildew was controlled in treatments and 2 with Pallitop. In treatment 3, shoots attacked by powdery mildew were elimin ted by hand. Scab has not been a problem in 1995. (Table 100) In 1995, no remarkable differences were observed between susceptibility of tl cultivars as in the previous years. No scab control was carried out on the CPF selections Ecolette and CPRO-78039-27, since these are scab-resistant. Fruit tree canker (Nectria galligena) Captan treatments were carried out against fruit tree canker in treatments 1 and 2. treatment 3, canker wounds were only cut out. Damage was recorded in winter 199 (Table 101) The canker infection has been continuously increasing from the beginnin In particular canker on the shoots increased greatly. (Figure 18). Weed control Treatment 1 : All methods and products used are in agreement with tl guidelines for IFP. These products were satisfactory. Treatment 2: Maximum 2.25 litres Roundup was used. Reduction of herbii 136 A.R. 1995 Research Station for Fruit Growing de use was achieved by narrowing the weed-free strip to 50 cm. 'reatment 3: Maximum 0.5 litre Roundup per hectare was used. Reduction of herbicide use was achieved by narrowing the weed-free strip to the width of the small strip on which the trees are planted (30 cm). Fruit tree canker in IFP 1991-1995 Product (g/ha) Labour In min. shootinfection wood>1 yr x 10 I trial1 trial 2 WMA trial 3 igure 18. Canker: Treatments and damage in three systems. able 101. Control measurements and damage of fruit tree canker in 1995 reatment Control measurements Number of canker wounds per 'eatment in 1995 2 x 187 g captan 4 2 x 125 g captan 11 7 137 A.R. 1995 Research Station for Fruit Growir Useof pesticides 80 percent of the pesticides used were fungicides, mostly for scab control. Sec control was the same for the 3 treatments and therefore the differences between the treatments were only marginal. (Table 102). Table 102. Use of pestcides (in kg a.i/ha) in 1995 Treatment 1 Treatment 2 Treatment 3 fungiciden Captan 24.2 23.3 21.2 Koper 2.3 2.3 - Score 0.2 0.2 0.2 Pallitop 1.8 1.3 - Scala 0.4 0.4 - Total fungicides 28.9 27.5 21.4 insecticiden Pirimor 0.2 0.2 0.2 Undeen - 0.5 - Zolone 0.6 - - Dimilin - 0.2 - Imidacl. 0.1 - - Dipel - 1.0 - Total insecticides 0.9 1.9 0.2 herbiciden Roundup 0.8 0.8 ,0.2 Diuron 0.6 - - Butisan S 0.4 - - Total herbicides 1.8 0.8 0.2 Total 31.6 30.2 21.8 crop protection Useof growth regulation The choice for the type of growth regulation in the 3 treatments was based on tr following considerations: in treatment 1 all legal growth regulators could be used, necessary. In treatment 2, carbayl was omitted because it kills beneficial insects, beir a broad spectrum insecticide. In treatment 3 only GA4+7 was used and thinning w< done by hand. Useof theenvironmental yardstick When choosing pesticides and growth regulators the environmental yardstick for 138 A.R. 1995 Research Station for Fruit Growing able 103. Environmental score per treatment in 1995. roduct Total score per product per treatment in 1995 water soil groundw. reatment 1 oper 0 69 23 aptan 37830 291 0 jpareen 1440 4 18 allitop 140 0 0 cala 10 2 28 core 20 78 0 alone 20400 0 0 rimor 330 132 0 lidacloprid 0 1 490 utisan S 8 0 40 iuron 8 8 3 aundup 0 0 0 otal treatment 1 60186 585 574 'eatment 2 oper 0 69 23 aptan 36530 281 0 jpareen 1440 4 18 allitop 100 0 0 :ala 10 2 28 core 20 78 0 ipel 0 0 0 milin 1840 9 0 rimor 440 176 0 ndeen 1800 270 10000 Dundup 0 0 0 3tal treatment 2 42180 889 10069 eatment 3 aptan 33280 256 0 slan 600 1 0 :ala 10 2 28 ;ore 20 78 0 rimor 440 176 0 aundup 0 0 0 ital treatment 3 34350 513 28 139 A.R. 1995 Research Station for Fruit Growin pesticides was used. This yardstick makes it possible to compare the effects < different pesticides on soil organisms, water organisms and leaching to ground water. I 1995 it again became clear that the choice in integrated pest management is smal However, it is possible to achieve a great improvement by choosing the right pesticide; A great reduction in fungicide use could be achieved by using curative fungicides bi because of the danger of resistance of scab this is not a good strategy. Within th insecticides Undeen and Zolone are the most polluting products. (Table 103). Fertilization In treatment 3, 40 tons of stable dung per ha was used in Zeewolde before planting. I 1991, it was decided only to fertigate based on soil analyses. In 1992 and 1993, n fertigation was given. In 1994, 40 g nitrogen, 13 g phosphorus and 44 g potassiui was given. In 1995, fertigation was done with 19-6-20 starting 1st July. Production in 1995 There is only a slight difference in production between treatments 1 and 3 in 1995. Th production of treatment 2 is somewhat lower. Considering the production from tr beginning, treatment 1 has the highest, treatment 3 has the lowest production (Tab 104). Table 104. Production in 1995 and 1991 -1995 Treatment 1 Treatment 2 Treatment 3 Production in tonnes/ 51 45 49 ha in 1995 Production in tonnes/ 219 218 213 ha in 1991-1995 Fruit damage by 2.7 4.1 10.2 insects in % production Fruit damage by scab 0 0 0 in % production Labour AM labour except observation time was recorded during 1995. The most labour w£ required in treatment 3. (Table 105). By omitting chemical thinning and canker contre a lot of work had to be done by hand. Compared with treatments 1 and 2. an extra 2 hours were needed in treatment 3 for cutting out canker wounds and 20 extra houi were needed for hand thinning. For picking 135 kg/hour and for sorting 100 kg/hoi was estimated. 140 A.R. 1995 Research Station for Fruit Growing able 105. Labour requirement (hours/ha) in 1995. Treatment 1 Treatment 2 Treatment 3 id. picking and sorting 948 865 960 xcl. picking and sorting 189 187 219 conomical evaluation n evaluation has been undertaken to examine the economic value of the different eatments. These results are reported under project 103. arming systems research for scab-resistant apple cultivars real reduction in pesticide use in fruit growing is limited because of the fungicide use ïat is needed to control scab. This is the main conclusion of the farming systems jsearch with current apple cultivars. A real reduction can only be achieved when the ;ab problem has been solved. One way to overcome this problem is by growing of ople cultivars which are resistant against scab. The cultivation of scab-resistant jltivars is quite different from the usual cultivation because of the low fungicide use. herefore it is necessary to know this cultivation system well before introducing it on a irge scale in practice. For this reason, two fields were planted in spring 1994: a iological and an integrated growing system. The biological field is treated according to ie European guidelines for biological control. The integrated field is treated according ) the guidelines for integrated fruit growing. Three scab-resistant cultivars are planted i a single row of 2.75 x 1 m.: Vanda, Ecolette, CPRO-80015-25. he plant protection scheme is given in table 106. esults ertilization i the integrated field, fertigation was given with 19-6-6; in the biological field organic ianure was given and trees were irrigated. In 1994 leaf analyses indicated a large fference in potassium and nitrogen content of the leaves between both fields. In 1995 ie levels were equal. The scores for leaf colour indicate a greener leaf for the integra- d field. (Table 107) 141 A.R. 1995 Research Station for Fruit Growir Table 106. Crop protection scheme 1994 en 1995. Integrated farming system Biological farming system Fertilization 1994 60 kg K20/ 180 kg P205 fertigation/tree organic manure/ha 9gN 30 tonnes = 129 kg N 3gP 63 kg P 3g K 288 kg K 1995 10g N 20 tonnes 86 kg N 3g P 42 kg P 3g K 192 kg K Growth regulation 1995 root pruning root pruning Crop protection 1994 Peropal - predatory mites July predatory mites May mating disruption mating disruption 1995 Peropal sulphur Nissorun sulphur Eupareen - predatory mites July - Pirimor Spruzit Pirimor earwigs Undeen - Kilval - mating disruption mating disruption Weed control 1994 Roundup rotor hoe Finale removal by hand MCPA - Simazin - 1995 Roundup schoffelen MCPA/2,4-D handmatig verwijderen Simazin - Diuron - 142 A.R. 1995 Research Station for Fruit Growing able 107. Score of leaf colour in integrated and biological system (1= yellow, _____ 9 = green). Integrated system Biological system 994 7.976a 6.752" 995 7.8903 7.076" alues in one column followed by the same letter do not differ significantly (P = 0.05) rop protection became very clear that the early introduction (May) of predatory mites is very jccessful. uit tree canker was a big problem in 1995 in the biological field. Up to 2.8% of the ees had to be removed. CPRO-80015-25 was the most susceptible cultivar (Table 38). cab has been observed once on Ecolette. This infection did not increase. able 108. Infection of fruit tree canker (number canker wounds per tree) in Janua- ry 1996. Number of canker wounds per tree PRO-80015-25 0.25 ;olette 0.03 anda 0.03 'eed control the integrated field all herbicides used were approved by the guidelines for IFP. In the ological field, weeds were removed with rotor hoe (6 times). This was satisfactory, anks to the dry weather. rowth February 1996, growth was measured: number of shoots, increase of stem diameter id shoot length were recorded. For all measurements, there was an interaction îtween cultivar and system. This means that every cultivar reacts in a different way to e system it is grown in. The growth was less in the biological field, Ecolette had the rongest reaction: for Ecolette the difference between the two systems was the gest. ze and quality grading ie size was smaller in the biological field . This is not necessarily a problem, conside- ïg the way biological fruit is marketed. The fruits from the biological field have a itter colouring. 143 A.R. 1995 Research Station for Fruit Growin Conclusion Up to now, no other diseases, i.e. summer diseases, have been found. The farmin systems are still very new and those diseases are expected in an older orchard. Sea has been found only once. In this research two growing systems are followed, not as comparison, because every system has to reach its own aims and those aims can b different. It was found that different cultivars react in a different way to the system an this may be important in the future when considering cultivar choice. 144 A.R. 1995 Research Station for Fruit Growing .ist of chemicals rade name Common name 'ungicides en Herbicides aycor 25% bitertanol utisan S 50% metazechlor aptan 83% sp 83% captan 'imilin 25% diflubenzuron 'iuron 80% diuron upareen spk 50% tolylfluanide oper copper AF-95-001 50% mepanipyrim allitop 37% nitrothal-isopropyl irimor 50% pirimicarb oundup 36% glyfosate ubigan vlb 120 g/l fenarimol cala 400 g/l pyrimethanil core 10% difeconazol portak 450 g/l prochloraz opsin M sp 70% thiofanate-methyl '/ant extract lilsana ethanol-extract from leaves of Reynout- ria sachalinensis îsecticides dmire 10 g/l imidecloprid imethoaat 400 g/l dimethoaat imilin 25% diflubenzuron isegar 25% fenoxycarb AK 4 250 mg 2-11-tetradecenylacetate ndeen 50% propoxur olone-Flo 500 g/l fosalone 'rowth regulators ,mid Thin 8.4% or-naftylacetamide (NAAm) erelex 0.9 g GA3 per tablet erelex A4/A7 0.89% GA4+7 (50% GA4 + GA7) CC-product 400 g/l chloormequat 4017 10% benzyladenine ruitone NA 100 g/l o-naftyl acetci acid (NAA) 145 A.R. 1995 Research Station for Fruit Growir GA4-rijk mixture 10 g/l total GA (95% GA4 + 5% GA7) Promalin 19 g/l GA4+7 + 19 g/l benzyladenine Sevin 50% cabaryl TD2337-2 50 g/l as endothallic acid 146 A.R. 1995 Research Station for Fruit Growing Publications talkhoven-Baart, J.M.T. and A. Scholtens Meer aandacht voor vruchtdunning na wortelsnoei. (Fruit thinning after root pruning needs more attention). Fruitteelt 85(1995)6:14-1 5 lootsma, J. Werken met de smalle slanke spil. 1. Vertakken verkiezen boven 'verweren'. (Working with slender spindles. 1. Better branching than feathering). Fruitteelt 85(1995)3:12 Werken met de smalle slanke spil. 2. Boomvorm die weinig arbeid vraagt. (Working with slender spindle. 2. A tree with low labour requirement). Fruitteelt 85(1995)5:14 Werken met de smalle slanke spil. 3. Regelmatige produktie van Elstar vereist dunnen.(Working with slender spindles. 3. Regular production of Elstar requires thinning). Fruitteelt 85(1995)10:16 Werken met de smalle slanke spil. 4. M.9 sterk bij afzwakken groei. (Working with slender spindles. 4. M.9 strong with growth reduction). Fruitteelt 85(1995)16:18 Herinplant verbeterd door planten op een rug. (Replant improved by planting in a ridge). Fruitteelt 85(1995)34:16 Voorsprong met tweejarige bomen. (Head start with two-year-old trees). Fruitteelt 85(1995)47:16 »ijkstra, J., W.A.G.M. Jansen and Sj.Rinsm a Evita is opnieuw erg produktief. (Evita strawberry again very productive). Fruitteelt 85(1995)4:16 Uitstel bloemaanleg leidt tot lagere produktie. (Delay in flower initiation causes lower production). Fruitteelt 85(1995)15:16 nde, E. van den, L. Bfommers and M. Trapman Gaby: a computer-based decision support system for integrated pest management in Dutch apple orchards. Integrated Pest Management Reviews 1 (1996):147-16 2 ioddrie, P.D. Toprassen zijn kwart eeuw geleden beproefd. (Top cultivars had been tested 25 years ago). Groenten + Fruit/vakdeel Hard- en zachtfruit 5(1995)14:20-21 Een tijd van komen en een tijd van gaan. (A time to come and a time to go). Groenten + Fruit/ vakdeel Hard- en zachtfruit 5(1995)16:4-6 Kritiek was soms terecht, soms niet. (Sometimes criticism was right, sometimes it wasn't). Groenten + Fruit/vakdeel Hard- en zachtfruit 5(1995)18:6-7 Japanse rassen voldoen niet aan Nederlandse maatstaven. (Japanese cultivars do not conform to Dutch standards). Fruitteelt 85(1995)20:25-26 Der Anbauwert neuer krankheitsresistenter Apfelsorten. (Practical value of new disease resistant apple culivars). Obstbau Weinbau 32(1995)4:99-101 147 A.R. 1995 Research Station for Fruit Growin Groot, M.J. - A decision support system for fruit growing on farm level. Acta Horticulturae nr. 41 of the 4th ISHS-symposium on computer modelling in fruit research and orchar management. Groot, M.J.;A.J.P. van der Waart and B. Nieuwenhuize - Handel waardeert rood en groen met betere prijs. (Trade values red and green w'n higher prices). Fruitteelt 85(1995)21:14-15 Heijne, B. - Emissie verminderen moet kunnen. (Reductions of emissions must be possible Fruitteelt 85(1995)22:14-15. Jager, A. de - Hardheid van Elstar, een stevig kwaliteitsprobleem. (Firmness of E/star, a firm qualh problem). Fruitteelt 84(1994)51/52:12-13 - Voortgang pluktijdstiponderzoek. Voorspelling per perceel staat hoog op de agendi (Progress in picking date research. Prediction per parcel has all attention). Fruittee 85(1995)3:16-17 - Consument voorzien van kwaliteitsfruit. (Providing the consumer with quality fruit Fruitteelt 85(1995)7:10-11 - Voorlopige pluktijdstipbepaling 1995 volgens T-methode: 1995 iets vroeger dan 199<< (Provisional determination of picking date 1995 according to T-method: 1995 a litt earlier than 1994). Fruitteelt 85(1995)25: 1 2-13 Jansen, W.A.G.M. - Proef met plantmateriaal bij appel: knip- en tussenstambomen voldoen beter da eenjarige bomen. (A trial with apple planting material: snip trees and interstem tret satisfy better than one-year-old trees). Fruitteelt 85(1995)28:14-15 Jansen, W.A.G.M. and H.A.Th, van der Scheer - Vruchtkleuring regelen met fungiciden lukt lang niet altijd. (Stimulation with fru colouring with fungicides is not always a succes). Fruitteelt 85(1995)21:16-17 Jobsen, J.A. - Goede perenaanplant begint bij de boomkweker. (A good plantation of pears stan with the nurseryman). Fruitteelt 85(1995)31:17-18 Kemp, H. - Tussenstam onvermijdelijk bij teelt Verdi. (Interstem inevitable for growing Verdi Fruitteelt 85(1995)35:10-11 - Nieuwe pruimerassen aanbevolen voor de praktijk. (New plum cultivars recommends for practice). Fruitteelt 85(1995)39:10-11 Kemp, H., J.H. Bootsma, W.A.G.M. Jansen and J. Westerlaken - Wilmuta verbleekt. (Wilmuta fades pale). Fruitteelt 85(1995)31:14-16 148 A.R. 1995 Research Station for Fruit Growing emp, H. and M.C.A. van Dieren Nieuwe appelrassen. 1. Schurftresistentie staat voor de deur. (New apple cultivars. 1. Scab resistence is imminent). Fruitteelt 85(1995)50:16-18 laas, M.P. van der Nut van borium en zink rond de bloei nog niet gebleken. (Need of borium and zinc during flowering not obvious yet). Fruitteelt 85(1995)13:12-13 Boriumbemesting kan via fertigatie. (Borium fertilization is possible through fertigati- on). Fruitteelt 85(1995)13:14 laas, M.P. van der and E.A.M. Remortel Calciumopname dit voorjaar zeer goed. (Calcium absorption very good this spring). Fruitteelt 85(1995)30:10-11 leijer, R.J.M. Zo snel als verantwoord naar Heteren. (As quickly as responsible to Heteren). Fruitteelt 85(1995)49:14 links, A.K., P. van Deventer, J. Woets and E. van Remortel Development of thresholds based on pheromone trap cathes for control of leafroller moths in aplle orchards: a first report osten, A.A. van Met Pax begint een nieuw tijdperk. (A new period starts with Pax). Fruitteelt 85(1995- 7:12-13 Redstart, interessant voor hobbyisten, minder voor beroepstelers. (Redstart, an interesting cultivar for amateurs, less for professionals). Fruitteelt 85(1995)11:12-13 Resistentie-onderzoek kleinfruit van start. (The start of resistance research in small fruit). Fruitteelt 85(1995)24:10-11 Veel nieuwe kleinfruitrassen te bewonderen. (Many new small fruit cultivars to admire at open day). Fruitteelt 85(1995)26:12 Herfstframboos Galante zorgt voor verrassing. (The primocane fruiting raspberry cultivar Ga/ante, is a surprise). Fruitteelt 85(1995)33:20-21 jtter, H. de Nog geen alternatief voor afspuiten gevonden. (An alternative for late spraying against storage rot has not been found). Fruitteelt 85(1995)20:14-15 oelofs, F.P.M.M. Ook fruittelers vinden harde Elstar het lekkerst. (Fruit growers prefer firm E/star as we/1). Fruitteelt 85(1995)1:20-21 Schilvlekjes op Elstar: oplossing hoofdzakelijk zoeken in teeltmaatregelen. (Skin spots on Elstar: Solutions mainly in growing conditions). Fruitteelt 85(1995)20:12-13 Oplossing voor hol en bruin in Conference nog niet gevonden. (Solutions for brownhe- art in Conference pears not found yet). Fruitteelt 85(1995)10:12-13 Eerste adviezen tegen hol en bruin. (First recommendations to prevent brownheart in 149 A.R. 1995 Research Station for Fruit Growin Conference pears). Groenten + Fruit, vakdeel Hard- en zachtfruit 5(1995)8:8-9 Scheer, H.A.Th, van der - Schurft selectief bestrijden voorlopig nog een wensdroom. (Selective control of scab for the present still a wishful dream). Fruitteelt 85(1995)8:18-20 - Wortelrot verergert groeiproblemen bij perebomen. (Root rot aggravates growl problems of pear trees). Fruitteelt 85(1995)41:12-13 - Schurft valt meestal niet ver van de boom. (Scab orginates mostly in the ow orchard). Fruitteelt 86(1996)8:34-35 Schenk, A.M.E. - Development of an integrated and biological growing system for scab resistant app cultivars. Acta Horticulturae (in press). 3rd ISHS-symposium on IFP. Schenk, A.M.E., C. Dekker and H. Veijer - Opbouw evenwicht vraagt tijd. Biologisch mijtenevenwicht nader bekeken binne geïntegreerde fruitteelt. (Building up balance takes time. A closer look to biologic mite balance in the integrated fruit control). Fruitteelt 85(1995)18:14-15 - Ecolette, schurftresistent appelras van eigen bodem. (Ecolette, a national sea resistant cultivar). Fruitteelt 85(1995)26:14-15 Schottens, A. - Diverse snoeimethoden zetten weinig zoden aan de dijk. (Several pruning methoc gets you nowhere). Fruitteelt 85(1995)2:12 - Autumn Bliss is prima door te telen. (Autumn Bliss an excellent autumn bearin cultivar). Fruitteelt 85(1995)2:14 - Meertaksysteem geeft hogere produktie. (Branch system gives a higher production Fruitteelt 85(1995)4:12 - Houtsnippers onderwerken vraagt weinig stikstof. (Ploughing in wood cutting require not much nitrogen). Fruitteelt 85(1995)7:16 Tromp, J. - In klimaatkamers geen enkel effect aangetoond. (Not a single effect proved in climax rooms). Fruitteelt 85(1995)4:20-21 Tromp, J. and Ch.A.R. Römer - Klimaat beïnvloedt de vorming van veren. (Humidity and soil temperature are bot important. Climate influences feather formation). Fruitteelt 85(1995)9:16-17 - Temperatuur vroeg in teeltfase van belang voor plukrijpheid. (Temperature in th cultural phase important for harvest ripeness). Fruitteelt 85(1995)1 5:20-21 - Zomertemperatuur nauwelijks van belang voor plukrijpheid. (Summer temperature < scarcely important for harvest ripeness). Fruitteelt 85(1 995)23:14-15 - Invloed van temperatuur op plukrijpheid anders dan verwacht. (Influence of temperate re on harvest ripeness different than expected). Fruitteelt 85(1995)50:14-15 Wagenmakers, P.S. - Teveel lichtopvang kost kwaliteit. (Too much light interception' reduces quality 150 A.R. 1995 Research Station for Fruit Growing Groenten + Fruit/vakdeel Hard- en zachtfruit 5(1995)26:8-9 Hoge bomen vangen veel licht. (High trees catch much light}. Fruitteelt 85(1995)28:- 12-13 Kwaliteit: meer dan gewone teelt. (Quality: more than usual cultural methods). Fruitteelt 85(1995)50:12 Light relations in orchard systems. Sonderheft, Mitteilungen der Gesellschaft zur Förderung der Forschungsanstalt Geisenheim, 1995, pp.34-37 éghelyi, K. and H.A.Th, van der Scheer Gyökergombäk Hollandiéban. Birs anyatelepak és körtések növekedési rendelle- nességei (Root rot fungi in The Neherlands. Growth problems in quince stool beds and pear orchards). Kertészet és Szölészet 44(1995)47:8-9 /agenmakers, P.S. and O. Callesen Light distribution in apple orchard systems in relation to production and fruit quality. Journal of Horticultural Science 70(1995)6:935-948 /agenmakers, P.S. and S.J. Wertheim M.27 geeft betere vruchtkwaliteit dan M.9. (M.27 renders better fruit quality than M.9). Fruitteelt 85(1995)12:22-23. /ertheim, S.J. Teelt van walnoten wellicht haalbaar. (Culture of walnut, perhaps feasible?). Fruitteelt 85(1995)51/52:40-41 /ertheim, S.J. and J. de Groene Veel meer veren bij eenjarige appelbomen. (Many feathers possible on one-year-old trees). Fruitteelt 85(1995)17:16-17 /ertheim, S.J., J. Bootsma and A. Scholtens Zwart bij peer. Dracht in het spel. (Black-skin discoloration in pear; fruit bearing plays a role). Fruitteelt 85(1995)17:20-21 Zoets, J. and H. Stigter De nieuwste plaag heet anjerbladroller. (Carnation leafroller as a new pest). Groenten en Fruit/Vollegrondsgroenten 5(1995)8:12-13 151 A.R. 1995 Research Station for Fruit Growin - Veel meer veren bij eenjarige appelbomen. (Many feathers possible on one-year-ol trees). Fruitteelt 85(1995)17:16-17 Wertheim, S.J., J. Bootsma and A. Schottens - Zwart bij peer. Dracht in het spel. (Black-skin discoloration in pear; fruit bearing play a role). Fruitteelt 85(1995)17:20-21 Woets, J. and H. Stigter - De nieuwste plaag heet anjerbladroller. (Carnation leafroller as a new pest). Groente en Fruit/Vollegrondsgroenten 5(1995)8:12-13 152 ist of Entries ipple - GoldRush (Co-op 38) cultivars 44-47 - Gris Braibant - 8S-27-43 - Jonagold - 8S-32-62 - H 1203 - Ahrina - Melodie - Ahrista - NY 66305-139 - Ambro - Otava - BFA 80/2-10 - Rode Boskoop - BFA 80/2-29 - P 1 300 - BFA 81/19-24 - P 1302 - BFA 81/19-47 - PH-FL-GR 86/3 - BFA 81/19-57 - PH-FL-RU 86/1 - BFA 81/19-76 - PH-FL-RU 86/3 - BFA 81/19-82 - PH-FL-RU 86/5 - BN 3/43 - PH-GR 1/79 - BN 26/245 - Pi-A-2,209 - Braeburn - Pi-A-3,129 - Co-op 29 - Pi-A-25,286 - Co-op 34 - President Roulin - Co-op 36 - Prima - Co-op 37 - Priscilla - CPRO 78038-9 - Red Devil - CPRO 78039-18 - Releta - CPRO 81003-49 - Rene - CPRO 84001-30 - Retina - CPRO 84015-17 - SA 15/4 - Cox's Orange Pippin -SPAB 918 - Delcorf - SPAB 920 - Delrouval - Topaz - Discovery diseases 118 - Delblush - storage diseases 95-108 - Delorina - powdery mildew 60 - E 55/59 - scab 60,142 - Ecolette fruit quality 44-47 - Elise fruit development 79 - Enterprise (Co-op 30) - firmness - FAW 2151 - quality - FAW 7262 - ripeness - Fiorina - ground colour - Gala fruit ripening 44-47 - Gerlinde fruit size 58,63 - Golden Delicious fruit tree canker 140 153 - growth regulators (see there) - Pioneer - leaf abscission 58 - Sharpblue - leaf drop acceleration 120 - Sunshineblue - picking period 66 - Spartan - pollination 66 - diseases - seeds/fruit - fruit rot - production 22 - soil treatment - resistance - fertigation - scab 46,119 - growth - rootstocks 19 - harvest - B 491, CG 65, J 9, KSC 28, - advanced - M.9, M.27, 0 3, P 16, P 22 82 - delayed - russeting 26 - production - taste testing 47 Branching Arrangement 21 Calcium Biological control 118,130 - calcium fertigation Black currant 58 - decalcification Black skin discoloration pear 34 - computermodel Blackberry 60 - calcium fertigation (OCAFE) - cultivars Chemical thinning - Adrienne - Amid Thin - Bödermö - carbaryl - Chester Thornless - timing - Douglas - D4017 - G6 - GA4+ 7 - Kotata - TD2337-2 - Oregon Computermodel - Navako - calciumfertigation (OCAFE) - Silvan Cherry (see also sweet cherry) - Thornless Evergreen - cultivars Blueberry 66 - rootstocks 13, - cultivars Cultivars - Avonblue - apple - Cape Fear - black currant - Caroline Blue - blackberry - Denise Blue - gooseberry - Duke - hazelnut - Bluechip - pear - Bluecrop - pink currant - Blueridge - plum - Blue rose - quince {Cydonia ob/onga) - Brigitta Blue - raspberry - Collins - red currant - Elliot - strawberry - Flordablue - sweet cherry - O'Neal - walnut - Nelson - white currant - Nr. 131 Diseases - Nr. 139 - apple 154 - fruit tree canker 118 - magnesium content - scab 119 - nitrogen content - storage diseases 95,108 - phosphate content blueberry - potassium content - fruit rot 119 Fungicides 120 pear 118 - Colletrotichum acutatum - fruit tree canker - Nectria galligena root rot - Roesleria pallida conomics 73 - Roselina necatrix system - Sphaeroteca mors-uvae - decision support system - Venturia inaequalis - ecological system Gooseberry 58 - model - cultivars - prices - Captivator - quality - Cirens nvironmental yardstick 138 - Greenfinch eathering 19 - Hinnomäkii (geel) ertigation 110 - Hinnomäkii (rood) 19-6-6 - K1-15-17 19-6-20 - Kozackoh Agrasol'F311 - Resistenta Agrasol'F313 - diseases fruit quality - powdery mildew 120 - acid Growth 79 - blush - fruit - calcium - shoot - dry matter Growth regulators 25 - firmness - Amid Thin - ground colour - Ó-naphthyl acetic acid (NAA) - sugar - auxin-conjugates - starch - benzyladenine (BA) growth - carbaryl - fruit growth - gibberellic acid (GA3) - shoot growth - gibberellins A4/A7 (GA4+7) ertilization (straw) berries 116 - indolebutric acid (IBA) lowering dates 7 - Promalin apple - TD 2337-2 (endothallic acid) pear Harvest 70 plum - advanced ruit tree nursery 19 - blueberry ruit quality 30,109 - raspberry (tunnel) firmness 124 - delayed - Boskoop - blueberry - Cox's Orange Pippin - raspberry (tunnel) - Elstar Hazelnut 14-18 - Jonagold - cultivars firmness decrease 104 - Butler mineral compound 104 - Camponica - calcium content - Casina 155 - Comen - Elstar - Corabel - Cox's Orange Pippin - Daviana - James Grieve - Emoa 1 Mutants 48 - Emoa 2 - Conference - Emoa 3 - Cox's Orange Pippin - Ennis - Delcorf - Fertile de Coutard - Elstar - Garibaldi - Jonagold - Gutav's Zeiler - Rode Boskoop - Lang Tidlig Zeiler Nematodes 121 - Impériale de Trebizonde Nutrients 11C - INRA H 105-28 Optimum harvest date 82-94 - Istarski Dugi - apple - Jemstegaard 5 - Boskoop - Lansing - Elise - Montebello - Elstar - Morell - % blush - Mortarella - anthocycane - Negret - chlorophyl - Noccione - full bloom - OSU 023-17 - harvest index method - OSU 039-44 - mineral content - OSU 042-89 - meteorological method - OSU 167-02 -PLUKY - Palaz - prediction of harvest date - Pauetet - thinning - Riccia di Talanico - T-method - Romai - T-stadium - Rote Zellernuß - Jonagold - Tombul Ghiaghli - Golden Delicious - Tonda Gentile delle Langhe Pear - Tonda di Giffoni - black skin discoloration 34 - Tonda Romana - cultivars 4£ - Tombul - Bautomne - Webb's Prize Cob - BP 9627 - White Filbert - Conference - Willamette - Dolacomi (Jowil®) - Witpit Lambertsnoot - Delbuena (Peradel®) Integrated fruit production 132 - Delmoip Integrated biological control 118,130 - Doyenné du Comice Light perception 21,30 - Gieser Wildeman - light utilisation - Orcas - rootstocks - Saint Remy - M.9 - Triomph de Vienne - Ottawa 3 - Verdi - P16 - diseases 11£ - P22 - fruit tree canker Models 82 - root rot 156 fruit quality 49,50 - Pandemis heparana - dark fruit tree pollination 53 tortrix - fruit set - Spilonota ocellana - bud moth - fruit size/ weight Picking date 82 - good seeds/fruit Pink currant 56 growth regulators 25 - cultivars root pruning 28 - Rosa Sport storability 106 Planting 21 taste test 49,50 - ridges esticides 118 Planting density 21 antagonists - apple - Binab T - Elstar - SchAA 4283-03 - Fiesta - Trichoderma sp. - Jonagold - Trichodex Planting system 21 fungicides Plum - Aliette - cultivars 51 - BAS 490 F - Carpatin - Baycor - Excalibur - Delan Flowable - Fl 70-S-483 (Firenze 90) Dorado - Ive Luxan Captan 83% spp - Julia (Cacak 2747R) - Luxan koperchloride - Jefferson - Luxan TMTD 80% spp - Jubileum manganese containing fungicides - Pitestean SchAA 10780 - Reine-Claude Souffriau Score - V66071 Sportak - Valor Topsin M spp - fruit quality 51 Tridal - fruit weight fungicide resistance - fruit set plant extract - picking period - Milsana - production ests 129 - taste Adoxophyes orana - summerfruit tor- Pollination/self pollination 53 trix Pratylenchus penetrans 121 Archips podana - fruit tree tortrix - bacteria Atractotomus mali - to lack apple - plant material capsid - preceding crop Cacoecimorpha pronubana - carnation - rootstocks leafroller - soil disinfection Campy/omma verbasci - mullein bug Pruning 28,32 Cydea pomonella - codling moth Quality 30 Dysaphis plantiginea - rosy apple - acid aphid - dry matter Edwardsiana rosae - fruit tree leafhop- - firmness per - measure Frankliniella occidentalis - Western - red blush flower thrips - sugar 157 - starch - Rossana - taste - Ruby Quince {Cydonia oblonga) 18 - Terri Louise - cultivars - summer bearing cultivars - Agvambari - 71/11/153 - Bourgeault - 88/1605-1 - Champion - 87/15/98 - Ekmek - Augusta 66,6 - 1/18 - Algonquin - 1/21 - Balder - I/25 - Beskid - Leskovacka - Comox - Limon - Elida - Ludovic - Eversdijk - Morava - Gaia - Portugal - Glen Ample - Rea's Mammoth - Glen Clova - Ronda - Glen Coe - Seker Gevrek - Glen Gary - Serbian - Glen Lyon - Shams - Glen Magna - Sobu - Glen Moy - Vranja - Glen Prosen - fruit quality - Glen Rosa - fruit shape - Glen Shee - fruit weight - Gradina - picking period - Julia - production - Marwé - tree habit - Meco - tree volume - Meyer - vigour - Multiraspa - winter hardiness - Nootka Radiation 6 - Pechts Gigant Rainfall 6 - Penhues Raspberry 60 - Proma - cultivars - Redsetter - autumn bearing cultivars - Resa - All Gold 66 - Rubacca - Autumn Bliss - Rumiloba - Autumn Cascade - Rutrago - Dinkum - Schönemann - Favourite - Tulameen - Galante - Wavi - Joan Squire - harvest - Kiwi Gold - advanced - Luilin - delayed - Medway Yellow Red currant 56-5 - Polana - cultivars - Princesse - Cocagne 158 - Fay's Prolific - calciumchloride - Fertöd - Stip-Stop - Heros - cultivars - Herosta - CPRO 78038-9 - Hron - Jonagold mutants - Jodes - Jonagored - Jonkheer v. Tets - Jonaveld - Junifer - King - Laxton no.1 - Navajo - Laxton Perfection - Schneica B - Losan - Wilmuta - Maraton - Elstar Mivana - pear 106 Mulka - cultivars Präkanda - Conference 108 Prince Albert - post-storage treatment Red Lake - heating Redstart Redpoll - pull-down Redwing - skin spots Rode Rebel - pre-storage treatment 95 Rotet - quality - Rovada - firmness Rubigo - harvest index - Stanza - optimum harvest date Traubenwunder - storability Vitan - taste oot pruning - taste research 47 pear 28 - acid content ootstocks - background colour apple 8 - firmness cherry 13 - ripeness cald 99 - sugar content alfafarnasene (AF) - taste tests 108 anti-oxydanten - cluster fruits CTH - solitary fruis ethylene content Storage conditions 100-106 Jonagold - ULO storage vitamin C Storage disorders 95-108 vitamin E - brownheart hielf-life 100 - cavities oil 102 - core rot decalcification - internal browning ground water table - internal disorders rooting depth - overstored soil type 86 - skin spots torage 95 Strawberry apple - biological control 132 - calcium - cultivars - calciumnitrate - in the open 54 159 - Elsanta Taste testing - Lambada - apple - Thuriga - pear - everbearers 54,55 Temperature - CPRO 1036 ULO-storage 10 - Darsival - antagonists - Evita - Cryptococcus laurentii - Mara des Bois - Bacillus subtil lus - Rapella - Sporoblomyces rosens - Sunset - C02 increases - Tango - rot Sweet cherry 51,52 - Botrytis cinerea - cracking - Gleosporum - cultivars 56 - Nectria galligena - 13S-5-22 - Penicillum - 13S-49-24 V-hedge - 13S-35-43 Walnut - 18-15 - cultivars 1 - Celeste Water application 11' - Fercer (Arcina®) Weather conditions - Giorgia White currant - Hartland - Karina - Kordia - Lapins - Magar (Garnet®) - Maru (Ruby®) - Merchant - Nanni - Newstar - Noire de Meched - Nordwunder - Regina - Schneiders Späte Knorpelkirsche - Somerset - Sonnet (13S-39-51) - Starking Hardy Giant - Sumgita (Canada Giant) - Summit - Sweetheart - Sylvia - Techlovan - Vega - Vernon - fruit quality 52 - firmness - fruit weight - picking period - production 160