Fruit Research Station
annual report 1997
FPO
Lingewal 1 6668 LA Randwijk The Netherlands
Phone: +31 488 473700 Fax: +31 488 473717 e-mail: @fpo.agro.nl
nformation contained in this report may not be reproduced in total or in part without aermission. Neither the authors nor the Fruit Research Station can accept any liability of loss, damage or injury resulting from application of any concept or procedure in or derived from any part of this report.
SSN 1381-6594 3rice: DFL 27.50 A.R. 1997 Fruit Research Station
The research on fruit growing is funded by the Ministry of Agriculture, Nature Conser vancy and Fishery, Landbouwschap and Productschap voor Siergewassen (PVS).
Ministerie van Landbouw, Natuurbeheer en Visserij Postbus 20401, 2500 EK Den Haag Tel.; 070 3793911 landbouw, natuurbeheer en visserij
Landbouwschap Prinsenvinkenpark 19, 2585 HK Den Haag Landbouwschap Tel.: 070 3526666
OryP üOV Productschap voor Siergewassen Postbus 93099, 2509 AB Den Haag Tel.: 070 3041234 A.R. 1997 Fruit Research Station
CONTENTS PAGE
Remarks on the brands of pesticides and herbicides 1 Board 2 Staff 3 Statistics 6 Weather and full bloom data 7 Department of Pomology and Economics
Top Fruit and Nursery ^ootstocks and interstems for pome and stone fruit 10 [apple- pear- plum) Unusual fruit crops 16 [hazelnut and walnut - quince) Wanting systems and light utilisation 17 [planting systems with pear)
Modelling fruit production and quality 19 [measuring light interception under direct light conditions)
Evaluation of growth regulators 19 [BAS 125 10W)
3rowth control apple and pear 21
High density plantings of sweet cherry 21 tree shapes and rootstock system trial 114-Wi9321) :ruit quality and cropping level 23
"hemical thinning 26 evaluation ofmixtures of benzyladenine and carbaryl - auxin-conjugates - chemical :hinning of pear - international thinning trial with Elstar)
Delblush/Tentation® . 33 russeting control) A.R. 1997 Fruit Research Station
Evaluation of Top Fruit Cultivars
Pollination of pome and stone fruit 34 (germination of pollen - crossings)
Fitting of apple cultivars in sustainable production systems and cultivar testing with apple 37 (research at Wilhelminadorp/Randwijk - clone and mutant trials at Wilhelminadorp - clone and mutant trials at Horst, Randwijk and Zeewolde)
Fitting of pear cultivars in sustainable production systems and cultivar testing with pear 47 (resaerch at Wilhelminadorp/Randwijk)
Fitting of plum and sweet cherry cultivars in sustainable production systems and cultivar testing with plum and sweet cherry 5C (research at Wilhelminadorp/Randwijk - cultivar trials with sweet cherry at Rillaai (Belgium) - cultivar trials with sweet cherry in Ahrweiler (Germany))
Small Fruit
Cultivar testing with strawberry 54 (evaluation of everbearing cultivars in the open)
Cultivar testing with strawberry 5£ (comparison of Elsanta from different origins)
Cultivar testing of bush and cane fruit crops 61 (first evaluation of blueberry cultivars)
Development of methods for an early and late harvest of bush and cane fruits 62 (delayed harvest of blueberry due to use of rain cover)
Economics and Farm Management Analysis
Root pruning 6*
Integrated fruit growing 6'
Plant Nutrition and Fruit Quality
Storage and Quality
Optimum storage conditions and ability to use storage techniques on fruit 6! (new varieties) A.R. 1997 Fruit Research Station
Storage ability of cherries 65
Reduction of internal disorders during storage of Conference pear 66
Storage of Delblush/Tentation® 67
Storage of Santana 68
Storage of blueberries 68
Differences between Cox mutants 69
Soil Science and Plant Nutrition
Improvement of the advisory system for fertilization of strawberries and other small crops grown in the open 69 (production - nitrogen uptake and growth - soil nitrogen - optimal nitrogen amounts - nitrogen balance)
Optimizing the water supply in relation to fruit quality and other aspects of apple and pear growing 73 (regrowth in 1997 - requirements for water status of the soil - how dry is the soil?)
Crop Protection
Testing of insecticides, fungicides and bactericides in fruit growing 76 (application of Zolone-Flo to apple may be phyto-toxic)
Control of rust in plum caused by Tranzschellia pruni-spinosa var. Discolor in 1996 and 1997 77
Biological control of diseases 78 (biological control of Botrytis cinerea in a belated strawberry culture)
Testing of insecticides and arcacides 79 (new pesticides for control of codling moth , Cydia pomonella)
Development of a propagation and production culture of strawberry in the open without chemical soil disinfection 86 crop rotation of strawberry and Tagetes patula (African Marigold) for control of the nematode Pratylenchus penetrans
Biological control of canker 87 control of canker on apple (caused by Nectria galligena) by a combination of fungicide applications and chemically induced accelerated leaf drop in 1995 and 1996)
3iological controlof strawberry diseases ...... 91 biological control of powdery mildew in a belated strawberry culture) A.R. 1997 Fruit Research Station
Biological control of pests in strawberry and bush and cane fruits 91
(sampling methods for thrips in a belated culture of strawberry under glass)
List of Chemicals 94
List of Entries 96
Publications 100
Bulletins and Publications on Fruit Growing 106
Donor members 107 A.R. 1997 Fruit Research Station
Remarks on the brands of pesticides and herbicides
"he dosages mentioned for pesticides and herbicides in this report refer to the commer çai products. It is unfeasible to mention all trade products with the same active ngredient. Use of certain trade name does not mean that it has preference over similar iroducts. Some of the experiments described in this report are carried out with :hemicals and/or concentrations not yet legally improved. A.R. 1997 Fruit Research Statio
Board (31 december 1997)
Board of the foundation of the Fruit Research Station
Executive committee J.A.M. Musters, Dinteloord, chairman H.W.M. Kurver, De Meern, vice-chairman J.G. van Haarlem, Buurmalsen, secretary
Other members F.J. van Beerendonk, Best G.A. van Haarlem, Buurmalsen Ing. C.G.M, van Leeuwen, Den Haag H.E.P. Reinders, Helden-Panningen H.F.M. Schrama, Biddinghuizen F.W.A. Vink, Den Haag G. de Weert, Rossum J. van Woudenberg, Niehove
Advisors Ir. J.M. Gerritsen, Den Haag J. Zevenbergen, Numansdorp Ir. R.J.M. Meijer, Wilhelminadorp A.R. 1997 Fruit Research Station
Staff (31 december 1997)
Director r. R.J.M. Meijer
Co-ordination and Information r. J.A. Jobsen
omology and Economics Dr.lr. S.J. Wertheim l"op Fruit and Nursery Dr. Ir. S.J. Wertheim drs. Ing. J.M.T. Balkhoven-Baart drs. Dr. P.S. Wagenmakers ).M. de Groene d. Tazelaar ng. J.H. Bootsma
valuation Top Fruit Cultivars ng. H. Kemp
mail Fruit \.J.P. van de Waart
conomics and Farm Management Analysis drs. Ir. M.J. Groot r. P. van Nieuwkoop
brary and Editorial Staff drs. M.M. Cremers-van Scherpenzeel
'lant Nutrition and Fruit Quality )r.lr. A. de Jager
Storage and Quality )r.lr. A. de Jager ng. F.P.M.M. Roelofs
Soil Science and Plant Nutrition r. M.P. van der Maas A.R. 1997 Fruit Research Statioi
Mathematics and Statistics E.A.M, van Remortel
Laboratory Mrs. Ing. L.M. van Westing Mrs. M.T.T. de Leeuw-Vereecken Mrs. A.M. Meerman-van de Repe Mrs. P.C. Rijk Mrs. D.T. Slazak
Crop Protection Dr.lr. B. Heijne R.H.N. Anbergen Mrs. Ing. W.A.G.M. Jansen vacancy H. Veijer Dr. L.H.M. Blommers Ing. H.H. Helsen
Data management ing. P.T.A.A. Rutten
Administration and Support Services J.A.M. Kouwenberg
Financial, personel and business administration Mrs. M.C. Schrier-Nijssen Mrs. J.G. Snaterse-van Loo J.J.C. Driessen
Clerical administration Mrs. T.L. Buizer-Schuit Mrs. P.E. van Vossen-Hopmans
Housekeepers Mrs. D.N. Nijsse-Hoogesteger Mrs. M.M. Stuck
Experimental Gardens and Engineering Ir. J.A. Jobsen
Wilhelminadorp J. de Schipper D.R.M. Acda M.C. van Maris A.R. 1997 Fruit Research Station
3.C. Oostdijk 3. Smits J. van Dalen
andwijk .L. Baarends .A. van Zuiddam l/V.C. van Eldik C.M. Sturkenboom \Ars. A.F. Alink-van Beek
ïreda ^/I.H. van de Rijt C. Oomen M.J.H.G. van Westen-Schuurbiers
Horst fh.S.G.M . Veens teewolde N. Lugtenberg :.J. Nagelhout J. Schoutsen s/lrs.T.J . Lugtenberg-te Borgel A.R. 1997 Fruit Research Statioi
Statistics
Statististical analysis
E.A.M, van Remortel
Data are analysed by analysis of variance (F-toets). Significant F-tests are followed b LSD-test (Least Significant Difference) for pairwise comparisons of treatment means. In the tabels of this annual report the results of the F-test are coded as: ns = not significant = indication for significance (P<0,10) * = significant (P<0,05) ** = strongly significant (P<0,01) # * * very strongly significant (P< 0,001)
The tables also include the LSD-value and the result of the LSD-test which is code with letters. Values followed by the same letter are not significantly different. The LSD value is calculated only after the F-test shows significance (P<0.05) Not calculate LSD-values are coded with nc.
Data are analysed with Genstat 5 release 3.2. A.R. 1997 Fruit Research Station
Weather and full bloom data
S. Wagenmakers able 1 lists data on global radiation, precipitation and temperature for Wilhelminadorp nd Randwijk in 1997. Long-term averages are presented for Vlissingen as these data fere missing for Wilhelminadorp. Because Vlissingen is closer to the North Sea, slight fferences occur between the two stations. The significance of these for fruit erformance is, however, small. The year 1997 started with a very cold spell, but this id not last long. February and March were warmer than normal. April, on the other and, had a great number of spring frosts. May, June and July had relatively high împeratures whereas August was probably the warmest month for centuries, being 4 egrees warmer than normal. Sunshine was limited in June, when it rained a lot. The ear 1997 was on average 0.9 degrees warmer than normal, and 1,5 degrees warmer n the basis of May-September. It was dry, except for June. Despite the higher jmperatures, there was no increase in sunshine. Randwijk, there was 10 % more rain than at Wilhelminadorp (February-December), emperature was almost 1 degree lower in spring and autumn, but 0.6 degree higher in ummer, compared with Wilhelminadorp. able 1. Global radiation , preciptation and temperature per i month in Wilhelminadorp (Wi, 1997) and Vlissingen (VI, * = average 1951-1 990). Globale radiation Preciptation Temperature (MJ/m2/day) (mm) (°C) Wi VI W VI Wi VI 1997 * 1997 * 1997 * anuary 89.3 78.8 1.8 65.9 -0.5 3.1 ebruary 134.0 143.6 83.6 46.3 6.6 3.1 larch 274.4 274.4 14.3 55.9 8.3 5.2 pril 459.5 412.0 27.1 45.6 8.5 8.0 lay 562.6 563.9 54.1 46.5 13.1 11.9 une 525.0 587.1 137.3 63.6 16.1 14.9 jly 561.1 563.4 47.6 68.7 17.3 16.7 ugust 533.7 489.1 28.5 80.1 21.0 17.0 eptember 372.7 342.7 13.5 70.9 15.3 15.2 ctober 205.7 209.6 83.8 81.4 10.9 11.7 ovember 70.5 97.5 48.1 76.9 7.1 7.2 ecember 53.3 61.7 66.4 72.9 5.7 4.5 /erage 320.2 318.7 50.5 64.6 10.8 9.9 ne high spring temperatures led to an early tree development. Unfortunately there A.R. 1997 Fruit Research Static were many spring frosts, starting March 21. The trees at Randwijk received overhee sprinkling 9 times between March 30-31 and April 22-23, with minimum temperature of -5° C. Full bloom (80 % open flowers) was early. Plums, cherries and pears flowere about two weeks earlier than usual during 1973-1992 (Table 2). The apples flowere 10 days earlier. Full bloom at Randwijk was one week later than at Wilhelminadorp. Fi bloom of Conference, Elstar, and Jonagold was April 16, May 10 and May 9.
Table 2. Data of full bloom of plum, cherry, pear and apple at Wilhelminadorp Cultivar 1993 1994 1995 1996 1997 Long-ter average* Opal 9-4 15-4 10-4 24-4 6-4 19-4 Victoria 4-4 13-4 6-4 24-4 6-4 18-4
Castor 25-4 1-5 28-4 2-5 21-4 Early Rivers 24-4 22-4 24-4 28-4 6-4
Conference 16-4 20-4 19-4 1-5 11-4 25-4 Doy. du Comice 20-4 27-4 25-4 3-5 19-4 30-4
Alkmene 25-4 4-5 30-4 7-5 26-4 4-5 Elstar 28-4 9-5 3-5 14-5 1-5 11-5 Jonagold 25-4 4-5 3-5 11-5 1-5 10-5 Golden Delicious 27-4 9-5 3-5 14-5 2-5 10-5 *) Long-term average of plum, pear and apple for voor 1973-1992, of cherry for 191 -1996, without 1989 -1993 .
Comparison of The Netherlands with Northern Italy
At Wilhelminadorp, there is on average 15-25 % less radiation whereas temperatun are 3-5 degrees lower than Northern Italy, based on weather data from Bologi (Universita di Bologna), Süd-Tirol (Versuchszentrum Laimburg) and Wilhelminado (KNMI) for 1991-1996. Early in the season, however, the differences between loca ons are much smaller. Full bloom is 22-24 days earlier in Italy than in the Netherland Incoming global radiation during the first six weeks following full bloom is about tl same at all locations, due to a longer day length at the higher latitude. Mean da temperature is only one degree lower than in Italy during this early period. The weath during cell division is therefore quite good in the Netherlands (Wilhelminadorp). Durii the summer, the Netherlands receive 10 % less sunlight at 1-2 degrees lower temper tures. As the season progresses, differences become larger. Radiation is about 30 less during the last weeks before harvest of Elstar (99-130 days after full bloom), ai up to 50% less before the harvest of Jonagold (131-155 days after full bloom), whii is unfavorable for quality characteristics such as size and red skin colour formation. T lower temperatures are, however, favorable. In the weeks before the harvest of Eist; the difference in mean daily temperature is 7 degrees. However, when harvest shoi be later than that of Jonagold, the northern climate is not favourable. Radiation is ve low, even when the temperature is fairly good.
8 A.R. 1997 Fruit Research Station
Fable 3. Radiation and temperature in Wilhelminadorp (Wi), Laimburg*'(La ) and Bologna"**(Bo ) Days after Radiation (MJ/m2,day) Temperature (°C) uil bloom Wi La Bo Wi La Bo 1-42 17.9 16.6 17.6 13.4 14.3 14.5 13-98 19.4 20.4 23.2 17.7 20.2 21.1 39-130 14.5 19.1 23.1 16.9 22.3 25.0 131-155 8.9 16.0 19.5 14.0 19.4 22.0 156-180 6.2 10.5 12.8 11.0 15.7 19.2 gemiddeld 14.9 17.3 19.9 15.1 18.4 20.1 Versuchszentrum Laimburg * Universita di Bologna A.R. 1997 Fruit Research Station
Pomology and Economics
Top fruit and Nursery
Rootstocks and interstems for pome and stone fruits
S.J. Wertheim and J.M.T. Balkhoven-Baart
Apple
New dwarfing rootstocks In the spring of 1991 a trial was planted to compare eleven new rootstocks with M.S and M.27. Test cultivars are: Elstar en Queen Cox. The planting distance is 3.25 x 1.2E m. The treatments are replicated two to four times with two trees per plot. Each plot is bordered by one tree of Regal Prince on M.9. Table 4 summarizes some results til 1997, where for each cultivar the rootstocks are arranged in ascending order of vigour The order was roughly similar for both cultivars, each vigour group indicated b\ horizontal lines in Table 4, contained the same rootstocks, but within each group the order was different. For both cultivars M.27 was the weakest. Most interesting are the rootstocks with a vigour in between M.27 and M.9. For Elstar five were in that range (AR 10.2.5, P.81, P.59, P.92, and Mac 39) and with Cox fou (the same minus Mac 39). However, none of these differed significantly from eithe M.27 or M.9. With Cox, all not yet mentioned rootstocks were of simialr vigour as M.9 but with Elstar P.60, Mark, C 6, and V 605-1 were significantly stronger. These latte four can therefore not be safely recommended for Dutch fruit growing as the chance exist for too much vigour. This leaves P.2 and V.605-3 as similar to M.9. For both cultivars it held that the more vigour the lower the production per unit o growth; a common phenomenon. It is also quite common to find that M.27 renders the smallest fruit. With Cox, V-605-3 was the sole rootstock with larger fruits than M.9 With Elstar no rootstock was better than M.9 in this respect. The Polish rootstocks P.59, P.60, and P.92 showed many burrknots and root suckers and have to be discarded for these juvenility symptoms. So far, five rootstocks look promising: AR 10.2.5, P.2, P.81, Mac 39, and V 605-3. AI seem more vigorous than M.27 and more dwarfing than M.9. Both P-numbers are o interest for their good winter hardiness, V-605-3 for its favourable fruit size with Cox and Mac 39 because in the USA higher calcium contents in fruits have been observed.
P.22, Voinesti 1and 2 In the spring of 1992, a trial was planted to compare the Polish rootstock P.22 and the Rumanian Voinesti 1 and 2 with M.9 and M.27 with Elstar as test cultivar. The plan distance is 3 x 1.25 m and the treatments are replicated six times with three trees per
10 A.R. 1997 Fruit Research Station
Table 4. Results apple rootstock trial 044-WJ9101 Rootstock Trunk Kg/ Fruits/cm2 Fruit circumf.(cm) tree trunk area weight (g) sprinq '97 1992-'97 1992'97 1992'97 Elstar M.27 13.3 a 50.1 a 25.5 ef 149 a AR 10.2.5 13.9 a 55.9 a 24.6 ef 162 bc P.81 13.9 ab 60.9 ab 26.6 f 158 ab P.59 15.7 abc 63.3 abc 23.7 ef 159 ab P.92 16.5 bed 73.2 bed 21.5 def 164 bc
Mac 39 16.9 cd 74.0 bed 20.6 cdef 166 bed M.9 17.9 cd 84.1 d 19.8 bedef 176 e P.2 18.7 de 83.9 d 19.3 bede 168 bede V 605-3 19.2 def 80.5 d 16.6 abed 174 de
P.60 21.1 efg 85.8 d 15.3 abed 166 bed Mark 21.9 fg 88.9 d 14.5 ab 172 cde C 6 23.2 g 78.8 cd 11.4a 171 cde V 605-1 23.8 g 88.3 d 13.4 ab 167 bede
LSDoo i 2.8 16.3 6.9 10 F-test * * * * * * * * * * * * Cox's Orange Pippin * M.27 10.5 a 33.5 a 27.7 bc 150 a P.59 12.6 ab 63,0 bc 35.7 c 153 ab P.81 13.7 bc 60.4 bc 27.4 bc 160 bc P.92 13.9 bed 54.6 b 24.1 ab 161 cd AR 10.2.5 14.0 bed 54.5 b 23.2 ab 166 cdef
M.9 16.1 ede 77.1 def 23.3 ab 168 def P.2 16.4 de 70.9 cde 20.2 ab 170ef Mac 39 16.4 de 68.2 bede 20.8 ab 164 cde V 605-3 17.1 e 80.4 ef 20.1 ab 178 g
V 605-1 17.2 e 76.3 def 21.7 ab 162 cd Mark 18.3 e 87.4 f 21.4 ab 172fg P.60 18.3 e 73.3 cdef 18.5 a 165 cdef C 6 18.4 e 72.2 cdef 17.2 a 171 fg
LSD001 2.6 15.1 8.9 8 =-test * * * * * * * * * * * * *
slot. In Table 5 some results are given. After six years M.27, p.22, and Voinesti 2 have given very similar results. Voinesti 1 is not a dwarfing rootstock and moreover is not
11 A.R. 1997 Fruit Research Station precocious in cropping. Therefore, this selection can not be recommended. P.22 i ol interest because its great winter hardiness as has been proven in Poland. The wintei hardiness of Voinesti 2 is unknown, but given the country of origin it might well be greater than of M.27.
Table 5. Results rootstock trial 044-WJ9209 with Elstar Rootstock Trunk Kg/ Fruits/ Fruit circumf. (cm) tree cm2 trunk area weight (gj spring 1998 1992-*97 1992-'97 1992'97 M.27 14.8 a 42.9 ab 16.3 b 157 a P.22 14.8 a 45.7 b 17.0 b 156 a Voinesti 2 14.8 a 42.7 ab 16.3 b 156 a M.9 17.8 b 59.5 c 15.0 b 167 a Vionesti 1 27.5 c 36.3 a 3.8 a 179 a
LSD«,.,» 2.2 7.2 2.8 ne F-test *** *** *** ns
Tabel 6. Results apple rootstock trial 044-Wi93021 Rootstock Queen Elstar Golden Jonagold Wilmuta Cox Delicious Trunk circumference (cm) spring 1997 M.9 13.2 a 15.7 a 12.0 a 13.0 a Supporter 4 16.0 b 16.6b 13.0 b 16.4 b
LSDo.08 0.8 F-test (interaction)
Fruits/cm trunk circumference 1994-'96 M.9 15.1 b 14.2 a 23.7 b 14.7 b Supporter 4 12.9a 14.8 a 18.5a 10.6 a
LSD005 1.9 F-test (interaction)
Fruits/m3 tree volume 1994-'96 M.9 222.3 b 310.0 b 403.2 b 285.0 b Supporter 4 165.2 a 259.0 a 272.3 a
LSD005 36.6 F-test (interaction)
12 A.R. 1997 Fruit Research Station
Supporter 4 In the spring of 1993 a trial was planted to evaluate the German rootstock Supporter 4 (a selection from Pi 80 from Pillnitz) with M.9. Both rootstock were planted with four cultivars (Table 6). The planting distance is 3.25 x 1.00, 1.25 or 1,50 m, but since this had no bearing on the main outcomes results in Table 6 are averaged for these within- row distances. The treatments were replicated six times with three trees per plot. The trial was ended prematurely in the winter of 1996-'97 because Supporter 4 showed more vigour than M.9 and in Dutch fruit growing such a vigour is not sought. Averaged for the four cultivars, tree volume at the end of 1996 was 0.77 m3 for trees on M.9 3 and 1.08 m for Suppporter 4 (LSD005= 0.09; there was no interaction between cultivar and rootstock). In spite of this larger volume accumulated kg yield per tree was not different between the two rootstocks. Again averaged for the four cultivars M.9 trees rendered 40.5 kg and Supporter 4 trees 42.0; a non-significant difference (F-value 0.168). So, M.9 was more fertile. This was supported by the data on the production per unit of growth or tree-head voluem (Table 6). Fruit weight on Supporter 4 (192 g) was significantly greater than on M.9 (185 g); LSD005= 3. Undoubtedly, this difference is due to the lower fertility of Supporter 4.
Pear
In the spring of 1991, a trial with Conference and Pierre Corneille each on six root- stocks was planted at 3.50 x 1.50 m. The treatments were replicated four times with three tres per plot. Two quince rootstocks (Quince MC and BA 29) are compared with three Pyrus communis rootstocks; the American OHxF 333 and the French OH 11, 20 and 33. Table 7 gives some outcomes. Quince Mc was the most dwarfing of the rootstocks under test, but with Pierre Corneille OH 20 was of similar vigour. OH 33 proved the most vigorous rootstock. With both cultivars, Quince MC was also the most fertile. With Conference all other rootstocks had a similar yield efficiency, but with Pierre Corneille BA 29 and OH 20 were better than the others. Cinference fruit weight on the quinces was better than on the pears and given the high production on Quince MC fruit size was remarkably good. With Pierre Corneille all rootstocks gave similar fruit sizes. So, far Quince MC was the best rootstock. OH 20 has been patented in France.
C. 132 In the spring of 1993, a small comparison was planted with virus free C.132, a Caucasian quince selected at East Mailing years ago, and Quince MC. Earlier, in Wilhelminadorp C.132 of unknown virus status was found to be slightly more dwarfing than Quince MC. Test cultivars are Conference and Doyenné du Comice. With the atter, the pear rootstock OHxF 40 is also incuded. The treatments are replicated five times with two trees per plot. The planting distance is 3.40 x 1.50 m. Table 8 shows that till now C.132 and Quince MC were of equal vigour, but productivity of C.132 was less. Still, C.132 might be vaulable for its greater winter hardiness. OHxF 40 was clearly more vigorous than both quince rootstock. Moreover, it was less fertile and gave smaller pears. This number is therefore of no interest
13 A.R. 1997 Fruit Research Station
Table 7. Results pear-rootstock trial 044-WÏ9111 Rootstock Trunk circumf. Kg/tree Fruits/cm2 Fruit weighl (cm) trunk area
LSD005 1.8 nc 4.2 15 F-test * * * ns * * * * *
Pierre Corneille Kwee MC 20.5 a 120.5 c 16.6d 228 a BA 29 22.8 bc 117.9 be 12.6 c 237 a OHxF 333 23.9 c 95.1 a 9.4 ab 238 a OH 11 23.8 c 101.0 a 10.3 b 227 a OH 20 21.6 ab 90.4 a 11.7 c 218a OH 33 25.4 d 103.6 ab 9.0 a 241 a
LSD005 1.3 14.3 1.2 nc F-test * * * * * * * * ~
Table 8. Results pear rootstock trial 044-WJ9319 Rootstock Trunk Kg/ Fruits/cm2 Fruit circumf.(cm) tree trunk area weight (g sprinq 1998 1994-97 1994'97 1994'97 Conference Quince MC 18.6 a 34.4 b 6.6 b 192 a C.132 18.2 a 26.1 a 5.2 a 204 a
LSD005 ne 3.0 0.4 nc F-test ns * * ns Doyenné du Comice Kwee MC 19.9 a 49.0 c 5.9 c 265 b C.132 20.3 a 39.2 b 4.5 b 270 b OHxF 40 26.5 b 30.1 a 2.3 a 236 a
LSD0.0B 1.0 5.9 0.8 12 F-test * * * * * * * * * * * *
14 A.R. 1997 Fruit Research Station
Plum
In the spring of 1990, a trial was planted with Victoria on a number of rootstocks (Table 9) to see whether a more dwarfing rootstock could be found than St. Julien A. The planting distance is 4.00 x 2.75 m. The treatments are replicated three times with two trees per plot. Table 6 shows that only Prunus blireana was more dwarfing than the standard, but leaves did not look very healthy and the rootstock stem was very thin. Both phenomena indicate a sub-optimal compatibility. Therefore, this species can not be recommended. Possibly, further research is warranted. Most other rootstocks were equally vigorous as St. Julien A and 'Hollywood'was even stronger. Marianna 2624 gave smaller fruit than all other rootstocks and is therefore less interesting. The aromising French 'Ishtara' was as vigorous as St. Julien A but tended to be more aroductive. However, the difference with the standard was not significant. The also crench Marianna GF8-1 was very productive on a per tree basis, but per unit of growth similar to St. Julien A. So far, no good alternative for St. Julien A has come forward.
Table 9. Results rootstock trial with Victoria 044-Wi9031 Rootstock Trunk Kg/ Fruits/cm2 Fruit °. = Prunus circumf.(cm) tree trunk area weight (g) sprinq 1998 1992'97 1992'97 1992'97 °. blireana 19.1 a 33.0 a 22.4 d 54 bc vlarianna 2624 31.9 b 63.5 b 17.9 bed 49 a 5t. Julien A 35.0 be 88.3 cd 17.1 bc 56 c Reine Claude 35.8 c 85.9 cd 16.5 abc 52 b shtara 35.9 cd 97.7 de 18.2 cd 55 bc vlarianna GF8-1 37.7 cd 115.8 f 19.4 cd 53 b °. dasycarpa 38.5 cd 76.3 bc 12.1 a 55 bc vlyruni1) 38.5 cd 103.4 ef 17.2 bc 53 b Hollywood1) 39.7 d 83.6 c 13.1 ab 52 b
-^'-'0.05 3.8 13.7 4.8 3 :-test * # * * * * * * * * ) belonging to P. cerasifera
'nternational trial Jnder coordination of the French INRA institute at Pont-de-la- Maye, a trial was planted n the spring of 1994 with the rootstock mentioned in Table 10. Only the Russian VVA- was a Dutch addition to the trial and due to shortage only present with Opal. The jther test cultivar is Reine Claude Verte. The treatments are replicated four times with wo (Opal) or three (Reine Claude Verte) trees per plot. The planting distance is 4 x 2 n. With Opal, VVA-1 and Ferlenain were more dwarfing than St. Julien A and all others were equally vigorous. With Reine Claude Verte, too, Ferlenain is more dwarfing than he other rootstocks. Cropping was still low due to the poor weather during flowering ime of 1997. So, conclusions on this aspect can not yet be drawn. So far, fruit size seems good on all rootstocks involved.
15 A.R. 1997 Fruit Research Station
Table 10. Results plum-rootstock trial 044-WÎ9432 Rootstock Trunk Kg/ Fruits/cm2 Fruit circumf.(cm) tree trunk area weight (g) sprinq 1998 1996-"97 1996'97 1996-'97 Opal WA 1 20.0 a 6.43 a 5.1c 42 a Ferlenain 24.2 b 4.63 a 2.5 ab 41 a P8-13 25.7 c 7.15 a 3.2 b 42 a Jaspi 26.0 c 6.26 a 3.0 b 40 a Ishtara 26.1 c 6.65 a 2.9 ab 43 a St. Julien A 26.2 c 3.31 a 1.6 a 42 a
LSD005 1.4 ne 1.3 nc F-test * * * * * * * * ns
Reinde Claude Verte Ferlenain 24.7 a 4.4 c 2.6 b 36 a P-8-13 28.6 b 1.2 a 0.6 a 32 a Jaspi 29.2 b 1.5 ab 0.7 a 33 a Ishtara 30.5 b 2.1 b 0.8 a 35 a St.Julien A 29.7 b 1.0 a 0.5 a 34 a
LSD005 1.9 0.7 0.5 nc F-test * * * * * * * * * ns
Unusual Fruit Crops
S.J. Wertheim and H. Kemp
Hazelnut {Cory/us sp.) and walnut (Juglans regia)
S.J. Wertheim
The results achieved with these two crops have been recently summarized in twe papers in the English language (see list of publications in this report).
Quince [Cydonia oblonga)
H. Kemp
In the spring of 1988, a trial was planted with 14 quince cultivars, comprising one year-old maidens on Quince MC planted at distances of 4.75 x 2.05 meters. In 1991 the crop was very small due to spring frosts during flowering. From 1992 to 1996 production was good, with that of some cultivars being even very good. In 1997, th
16 A.R. 1997 Fruit Research Station
»roduction was only moderate to good, due to night frost damage. Up to and including 1997, the cultivars Agvambari, Bourgeault, Ekmek, Leskovacka, Rea's Mammoth, tonda, and Vranja produced well and regularly. n the spring of 1993, four cultivars were planted and a further four during the follo wing winter. All these cultivars, one-year-old maidens on Quince MC, were planted at a istance of 3.50 x 2.55 meters. In 1994, 1/18 and Morava gave the first fruits. In 1955 nd 1996, all cultivars yielded (rather) well, especially 1/18, 1/21, Morava, and Bencikli. i 1997, 1/18, Morava, Gukuz Gobeke, and Sobu produced well. Vt Randwijk, four cultivars - I/30, I/50, Balady Awad, and Leskovacka (as standard) - vere planted in the spring of 1996. In the spring of 1997, the new cultivar BQ 6-35 vas planted, as well as the standard cultivars Ekmek, Vranja, Agvambari, and Sobu, all n rootstock Quince MC. Up to and including 1997, the production was negligible.
T 1997, the quality of the jelly from 20 cultivars, growing at Wilhelminadorp, was ested for the first time on the initiative of an enthusiastic amateur fruit grower. For all he cultivars, the jelly was prepared in a standardized way. The final products were ated by the amateur fruit grower and some employees of the FPO. The differences in äste between the cultivars were considerable. In 1998, the test will be repeated if ossible.
lanting systems and light utilisation
\S. Wagenmakers, M. Tazelaar lanting systems with pear i spring 1988 a trial was set up at Wilhelminadorp with Conference on Quince C. Five lanting densities (2000-4000 trees per ha) and two arrangements (single rows and iulti-row bed systems) were planted. There was no yield in 1988 and 1989, and a mall yield (9 tonnes per ha) in 1990. Between 1990 and 1997, the mean production vas 49 tonne per ha. Planting density interacted with planting system. For the single ows, production increased with 41 ton per 1000 trees over 8 years. On the other and, planting density was not accompanied by an increase in production of the multi- ow systems. This effect was also recognized in the full-grown stage, as illustrated for 997 (Table 11). Production of single rows increased by 5.5 tonne per 1000 trees, vhereas there was no such trend for the multi-row systems. Multi-row systems roduced more than single rows at lower planting densities, but there was no differen- e between the two systems at higher densities. The highest production (400 tonne in ! years) was realized by single rows with at least 3500 trees per ha and multi-row ystems with at least 2500 trees per ha. ingle rows intercepted 9% less light (PAR) than multi-row systems (Table 12). Light -perception was linearly related with planting density (5% per 1000 trees, irrespective f planting system). In general, one percent of increase in light interception was îsponsible for 2.3 more tonnes of fruit over 8 years. Light interception increased from
17 A.R. 1997 Fruit Research Statio
67% at 2000 trees to 77% at 4000 trees per ha for the multi-row beds. In this range a higher light interception did not lead to more production.
Tabel 11. Production perh a (1990-1997 and 1997). Conference, Wilhelminadorp Trees/ha Tonnes/ha 1990-'97 Tonnes/ha 1997 Single row Multi row Single row Multiro w 2000 343 a 384 a 46.0 a 61.0 cd 2500 374 a 399 a 48.4 ab 66.3 d 3000 368 a 405 a 47.6 ab 53.0 a 3500 410 a 399 a 52.1 b 54.8 ab 4000 426 a 407 a 57.8 c 59.1 bc
LSDo.05 nc nc 5.5 5.5 F-test interaction ~*
Fruit weight was 190 g, averaged for 1990-1997, and in 1997 even 201 gram. Tha year, only 6% of the pears were smaller than 55 mm. Planting system did not affec fruit size, but fruits were slightly smaller at a higher planting density (-4 g per 100( trees). The effect of density on fruit size was only minor. In 1997, for example, onh 2.5% less pears above 65 mm were graded at 3000 trees per ha, compared with 200^ trees perha .
Table 12. Fruit weight (1990-1997) and light interception (22-7-1997, percentag of available diffuse light). Conference, Wilhelminadorp. Fruit weight Light interception 2000 197b 62a 2500 191a b 9b e 3000 191a b 67a b 3500 187a 71b c 4000 189a 74c
LSDn single row 192 a 64 a multi row 190 a 73 b
LSDo.oB nc F-test density * * system ns * ** interaction ns ns
18 A.R. 1997 Fruit Research Station
Modelling fruit production and quality
S. Wagenmakers and M. Tazelaar leasuring light interception under direct light conditions ght (PAR) interception has been measured in various apple and pear plantings. Earlier search has shown that the optimum light interception level was 60-70% of available ght, with regard to quality production. A higher light interception would lead to loss of uality production, whereas a lower light interception would produce too low a level of uality production per ha. This research was carried out under diffuse light conditions nd was thus dependent on the prevailing weather. Therefore, two methods were tudied to develop a reliable method for sunny conditions: 1. measuring with PAR ensors and 2. recording sunfleck patterns. The measurements were carried out in NS edgerows. A rectangular grid was laid from the middle of the tree row to the middle of ie adjacent row (E-W) and from tree to tree within the row (N-S) at an interval of 10 m. With the direct PAR method, the ratio in PAR between average light level on the round and above the trees was calculated. With the sunflecks, a value 0 and 100 (% ght interception) was given for an exposed and a shaded spot, respectively. The suits have been compared with a model in which light interception was calculated as function of orchard configuration and solar position (Wagenmakers, 1991. Agric. For. leteorol. 57, 13-25). ght interception according to the sunfleck measurements was 10 % lower than mulated by the model. The PAR direct light method underestimated the interception ven more, which might be partly due to the fact that the measured light was not only irect but also diffuse. This could, however, not explain the big difference, irect light interception according to the sunfleck method crosses diffuse light intercep- on. Apart from row orientation, this hour depends on Julian day: later in the season, lis hour is also later in the day. When this would be July 31 10:45 am (summer time, reliminary result for NS row), it should be 10 minutes later on August 10.The study rill be continued in 1998. valuation of growth regulators
J. Wertheim
AS 125 10W pple he new growth retardant BAS 125 10 W (prohexadione-Ca) was evaluated on Elstar ees on M.9 in theri sixth leaf plnated at 3.25 x 1.25 m. Two concentrations (125 and 50 ppm active ingredient) were applied once or twice (the first time at five to eight lfolded leaves on the extension shoots and in case of a second spray three weeks ter). Unsprayed trees served as controls. The treatments were replicated ten times ith one tree per plot. Due to spring frost the fruit set was limited to upper parts of the
19 A.R. 1997 Fruit Research Statio trees, so cropping was lower than it should haven been and shoot growth wa therefore enhanced.
Table 13. Results qrowth-retardant trial with Elstar 076 Ex 97026 Treatment Fruits/ 'Fruits/ Kg/ Fruit Total Mean Flower tree 100 fl. tree weight growth shoot cluster: clusters (g) m/tree length tree (cm) 1998 Untreated 37.7 a 14.6 a 5.9 155 a 65.02 c 47.2 b 247.4 a 1x 125 ppm 58.9 a 23.1 a 9.5 160 ab 36.71 b 39.0 ab 257.0 a 1x 250 ppm 54.0 a 21.9 a 9.2 172 c 32.80 b 42.6 b 263.4 a 2x 125 ppm 50.7 a 21.1 a 8.5 167 be 28.61 ab 35.7 a 227.2 a 2x 250 ppm 57.4 a 21.8a 9.2 162 b 22.02 a 33.2 a 237.8 a
LSDo.05 nc nc 9.6 9.69 8.3 nc F-test * * * * * ns
Table 13 summarizes the main results. Prohexadione-Ca inhibited shoot growth especially the two spays with 250 ppm. Fruit set as expressed in fruits per 100 flowe clusters and fruits per tree seemed enhanced by the retardant, but the differences wit the control were not significant. Fruit development, too, seemed promoted except aft« one spray of 125 ppm. In 1998, no diiferences in numbers of flower clusters wer found, but since the sprayed trees had less growth flowering intensity per m wa greater compared to control trees.
Table 14. Results Prohexadione-Ca trial with Conference 076- EX97112 Treatment Fruits/ Fruits/ Kg/ Fruit Total Mean Flower tree 100 tree weight growth shoot clusters flower (g) m/tree length tree clusters (cm) 1998 Untreated 32.8 a 18.8 a 6.7 208 a 51.23 b 47.5 113.7d 1x 125 ppm 34.7 a 20.2 a 7.3 203 a 21.08 a 40.3 110.4d 1x 250 ppm 36.7 a 20.4 a 7.8 220 a 26.08 a 49.0 79.5 b 1x 500 ppm 42.5 a 22.1 a 8.5 203 a 21.94 a 42.7 61.2 a 2x 125 ppm 40.0 a 21.0a 8.0 205 a 25.80 a 44.5 102.4 o 2x 250 ppm 33.4 a 17.5 a 7.4 219a 21.14a 42.2 81.7 b 2x 500 ppm 41.0 a 20.5 a 8.6 213 a 25.60 a 44.3 49.2 a
25.2 LSD005 nc nc nc 8.75 nc F-test ns ns ns * * * ns » * *
Pear On Conference pear, too, Prohexadione-Ca was evaluated. A trial was carried out c trees on Quince MC rootstock in their sixth leaf planted at 3.25 x 1.25 m. Thre
20 A.R. 1997 Fruit Research Station oncentrations (125, 250 and 500 ppm active ingredient) were applied once (five to ight enfolded leaves on the new extension shoots) or twice (three weeks after the first pray). Unsprayed trees served as controls. The treatments were replicated ten times /ith one tree per plot. Results were disappointing. After an initial inhibition of growing hoot tips, on many shoots side buds grew out and many of these shoots ended their rowth later than shoots from untreated trees. This regrowth lead to a bushy habit and probably also the reason that average shoot length was not shorter than that on ntreated trees. Still, the number of long shoots and hence the total growth was less n treated trees. The regrowth was perhaps also at least partly responsible for the egative effect of the regulator on the number of flower clusters in 1998. rohexadione-Ca had no negative effects on cropping or fruit weight (Table 14). In new ials, repeated sprays of low concentrations will be evaluated.
ïrowth control of apple and pear
'.M.T. Balkhoven-Baart
ince 1990 trials have been carried out to test the effect of root pruning on apple, iesults were published in Fruitteelt 82(1992)8, 83(1993)9 and 85(1995)6. The effect f root pruning on pear needs further testing. In 1997 trials started with the timing of Dot pruning on slender spindle and V-hedge Conference- and Doyenne du Comice- ees. In spring 1996 and 1997 super spindle trees of Conference and V-hedge trees of loyenne were planted in, half in or on top of the soil surface to test the effect on hoot growth. ligh density plantings of sweet cherry.
M.T. Balkhoven-Baart
ree shapes and rootstock trial 114-WÏ9321
1993 a trial was planted with 5 tree shapes; slender spindle, Le Page, super spindle nd cordons planted upright and in V-hedge. Slender spindle and Le Page were planted n rootstock Inmil (GM.9), Damil (GM.61) and Edabriz (Tabel ®), the other rootstocks rere only planted on Inmil and Edabriz. Planting density varied from 1,900 to 10,000 ees per ha. The trial was carried out in 4 replicates, two replicates were covered with lastic. A bird net was placed over the covers. Cultivar was Lapins with Sunburst as uard trees. Planting material consisted of 1.5 m long one-year-old unfeathered trees.
emperature measurements lastic covers were put in place in March 1995 . In spring 1995 minimum and maxi- lum day temperatures were measured in the middle of the trees at 1.5 m above the 3il surface. On cold days in April the minimum temperature was about 1.5 to 2.0 °C gher under the covers. Maximimum temperatures in May and June were not higher nder the covers. Possibly shading and condensation on the folie prevents warming up
21 A.R. 1997 Fruit Research Statio in the morning. In spring 1997 spring frosts after bloom caused Pseudomonas infectio which led to severe leaf damage. Leaf damage probably resulted in a severe June dror. Under the covers leaves were not infected and remained green. There was hardly an June drop under the covers. Trees in the first row next to the covers still showe brown leaves.
Production and fruit size After June drop it was clear that the trees under covers had a much higher productio than the trees without covers. The higher the planting density, the higher the product on per ha. Trees on Edabriz gave the highest production, as in previous years. Withoi covers trees on Inmil and Damil failed to produce well. Without covers, trees on Edabri still gave a good production which caused a lower fruit weight than trees on Inmil an Damil.
Table 15. The effect of rootstock on production and fruit weight (g) of Lapin grown with and without plastic covers Tonnes/ha good cherries 1) Fruit weight (g) Rootstock - folie + folie - folie + foli Inmil 1.3 5.7 10.1 11.! Damil 0.9 4.6 9.7 11.( Edabriz 9.6 14.2 8.9 10.«
Average 4.7 9.0 9.5 11. 1) Average over all growing systems 2) Weight average
With covers the fruit weight on Edabriz, Damil and Inmil was 2.0, 1.3 and 1.4 g high( respectively (Table 15). The highest densities (cordons) gave the smallest fruits.
Cracking In the wet summer of 1997 the plastic covers reduced the percentage of rotted an cracked fruits by 35% (Table 16). With covers there were no differences between tr rootstocks. Without covers Edabriz gave less rotted and cracked fruits than Damil an Inmil, but still 50%!
Table 16. The influence of the rootstock on the percentage of cracked fruits i Lapins, grown with and without cover in 1997. % rotten and cracked fruits 1) Rootstocks - folie + folie Difference betwec - folie and + folie Inmil 67.3 24.8 42.5 Damil 66.2 22.3 43.9 Edabriz 50.8 25.9 24.9
Average 60.3 24.8 35.5 1)Average of alle growing systems 2) weight average.
22 A.R. 1997 Fruit Research Station
'äste i 1996 taste of cherries grown under plastic covers was less than without covers, specially the highest densities produced less tastfull cherries. In 1997 there were no ignificant effects of the covers on taste. Cherries grown without covers scored 6.9 scale 1 to 9) , cherries grown under covers scored 6.6. Of course an interaction of äste with production per tree and fruit size has to be taken into account. The expecta- on that a high production results in less tastefull cherries did not come through, ossibly the bigger size of the cherries lead to a better score for taste.
'utrient uptake eaves from trees under covers had higher zinc, manganese and iron content. Contents f N, P, K, Ca and Mg were not influenced by the covers. Of course leaf quality played n important role here. Possibly higher soil temperatures under the covers facilitated utrient uptake. The dryer soil under the covers warmed up more easily than a wet soil.
'igour runk circumference measurements showed no increase in growth under the covers. tying trees of Edabriz l the trial descriped above Edabriz performed very well. Edabriz however had a large mount of trees that died without a clear cause. In other countries similar problems ave been reported. For this reason Edabriz cannot be recommended for practical use. ata from the trial was published in Fruitteelt 86(1996)37;16-18 and Fruitteelt 8(1998)12:12-13.
ruit quality and cropping level
.S. Wagenmakers and M. Tazelaar
trial was planted in March 1995 with Golden Delicious and Jonagold 'Novajo' in filhelminadorp and Bologna (Italy) to study the effect of crop load at three levels on uit quality with different rootstocks (M.9 and P22) and planting densities (3 * 1 and 3 0.60 m). Trees had been flower-thinned in 1996 and 1997. Flower clusters on the der wood were removed manually for 50 or 75% and were compared with trees that mained unthinned. On the one-year-old wood, 50 or 75% the clusters of trees were moved in 1997 on M.9 and P22. The top flower was left unthinned. Additionally, on jly 14 1997 the thinned trees were hand thinned: trees on P22 with 50% and 75% linning were thinned to 2 and 1 fruit(s) per cluster (bot one-year-old and older wood). ie unthinned trees did not receive additional hand thinning. With Golden Delicious, the ees on M.9 received similar treatments as those on P22. With Jonagold, additional and thinning in July was not necessary. oduction was determined by the thinning level, irrespective of the cultivar, rootstock id planting density. Unthinned trees produced 10% and 29% more than trees that ere 50% and 75% thinned, respectively (Table 17). For M.9, the production of inagold was the same as Golden Delicious. Trees on P22 produced less than on M.9.
23 A.R. 1997 Fruit Research Statio
Besides, the production of Jonagold on P22 was less than that on Golden Delicious Production per ha was higher at a higher planting density. Planting density had a mor pronounced effect on production for M.9 than for P22, but the relative increase i production was the same (41% more tonnes with 67% more trees).
Table 17. Production (tonnes/ha 1996+1997) averaged for Golden Delicious an Jonagold, two rootstocks and two planting densities. Thinning %) 50 75 78a 71b 60c
LSD005 4 F test * * * Rootstock M.9 P22 Cultivar -Golden Delicious 82a 66b -Jonagold 83a 48c
LSDa05 7 F test * *# Rootstock M.9 P.22 Distance (m) 1,00 68b 48c 0,60 97a 67b
LSD005 int. 5 F test * * Values followed by the same letter within a column or row do not differ significant (P<0,05)
Table 18. Fruit weight (q averaqed for 1996-1997). Thinninq (%) 0 50 75 Golden M.9 146 a 164 b 170 b P22 167 b 173 b 197 c
Jonagold M.9 197 a 201 a 221c d P22 207ab 216bc 228 d
LSDao6 10 F test *
24 A.R. 1997 Fruit Research Station
:ruit weight of Golden Delicious was 42 g less than that of Jonagold (averaged for 996 and 1997) . The largest fruits of Golden were similar to the smallest of Jonagold, îenerally, fruits on P22 were larger than those on M.9, except for the most intensively hinned Jonagold trees (Table 18). Thinning did not necessarily lead to bigger fruits. Mthough thinning promoted fruit weight of Golden on M.9 in general, there was no lifference in fruit weight between 50 and 75 % thinning, whereas the effect of hinning on P22 was absent for no thinning and 50% thinning. The latter also held lood for Jonagold: thinning only had an effect on fruit weight at the 75% level. ruit size was large in 1997: Jonagold had an average diameter of 85 mm (212 g). ven unthinned trees produced fruit of 83 mm. Fruit size of Jonagold was slightly mailer in 1996. The fruit of Golden were of a similar size in both years. Most fruit vere 70-75 mm. Unthinned trees produced slightly more fruit of 65-70 mm, whereas he highest thinning level produced more fruit with a diameter of 75-80 mm. lonagold fruits were colour-graded in five classes in 1996. Most fruit had 33-50 % red lush. In 1997, when fruits were graded on a percentage basis, fruit had 56% red lush. All studied factors affected fruit colour. Planting density had a negative effect, vhereas the more dwarfing P22 showed more colour than M.9. The colour difference >etween M.9 and P22 was similar to that of planting density. Thinning improved colour gnificantly, even when an effect on fruit weight was absent (Table 19).
'able 19. Percentage red blush (Jonagold, 1997) )istance (m) ,00 60b ),60 52a SD005 3 F-test * * * lootstock /1.9 52a 22 60b
"'-'0,05 ^ -test * * *
hinning {%) 48a 0 55b f5 65c
SD0,05 4 -test * * *
25 A.R. 1997 Fruit Research Statio
Chemical thinning
S.J. Wertheim, J.M.T. Balkhoven-Baart, and J.H. Bootsma
Evaluation of mixtures of benzyladenine and carbaryl
S.J. Wertheim
Apple In 1997, two trials were carried out on Elstar with the chemical thinner D4017 the contains benzyladenine (BA) as active ingredient. This compound is not yet registere for practical use. The aim of the trials was to see whether carbaryl concentrations ca be lowered but maintaining the thinning effect by addition of BA. Carbaryl is a insecticide and under pressure for environmental reasons. In all trials, D4017 wa applied with 0.1% Tween 20 wetter.
Table 20. Results thinninq trial Elstar 137-Ex97023 Treatment Fruits/ Kg/ Fruit Flowerini 100 flower tree weight index 1 2 clusters ) (q) 1998 ) 1. Unthinned 93.0 25.1 142 1.4 2. Hand thinned 66.1 19.8 156 1.5 3. D4017 5.0 mm 81.0 22.7 130 1.1 4. 8.0 mm 80.0 24.3 143 1.5 5. 12.2 mm 76.7 23.7 149 1.9 6. 15.2 mm 80.6 23.8 139 1.8 7. 21.2 mm 71.7 20.0 136 1.9 8. carbaryl 5.0 mm 74.2 23.5 148 1.1 9. 8.0 mm 73.8 21.0 153 1.6 10. 12.8 mm 75.4 24.4 165 1.4 11. 15.2 mm 54.2 19.4 177 1.4 12. 21.2 mm 66.2 22.4 162 1.4 13. mixture 5.0 mm 87.6 23.2 140 1.3 14. 8.0 mm 63.0 21.8 170 1.6 15. 12.8 mm 67.6 20.2 158 1.8 16. 15.2 mm 56.8 19.3 165 2.5 17. 21.2 mm 47.9 17.6 172 1.5 LSD001 19.6 27 nc F-test * ** 0.061 Differences within 1 column greater than the appropriate LSD-value are significar (P= 0.05) . 1) after correction for diferences in flower clusters/tree. 2) scale 1 = no to = abundant flowering.
In the first trial, timing of the mixture was subject of study. At 5.0. 8.0. 12.8. 15. and 21.2 mm average fruit diameter on the old wood, 100 ppm and 375 ppm carban
26 A.R. 1997 Fruit Research Station
/vere applied separately of mixed. Together with un unthinned and a hand-thinned ;ontrol there were 17 treatments. The experiment was carried out on trees on M.9 in heir seventh leaf. Treatments were in eight replicates with one tree per plot. Planting iistance was 3 x 0.80 m. Table 20 summarizes some outcomes. Fruit set was good ind thinning was needed as witnessed by the differences between unthinned and hand hinned controls. BA thinned only when applied at 21 mm and this hold for carbaryl as veil (15 or 21 mm). For carbaryl this is later than the customary practical recommenda- ions (12 mm). The mixture thinned over a geater time span (8 till 21 mm) showing that t has more potential than the compounds separately. Only some treatments had a lositive effect on fruit size (those with a fruit weight larer than 170 g). Rgression nalysis showed that carbaryl had a linear (negative) thinning effect with time of pplication. For fruit weight there was a positive linear effect. Per 1 mm later applicati- m time set decreased with 0.9 fruits/100 flower clusters and fruit weight increased vith 1.3 g. With the mixture, too, significant linear relationships were found and the ame values were 2.1 fruits and 1.5 g respectively. No curvi-linear relationships were ound. In 1998, all trees had an off-year. Only treatment 16 tended to have slightly nore flower clusters, but here too the number was insufficient.
'able 21. Results thinninq trial Elstar 137-Ex97017 'reatment Fruits Kg/ Fruit Flowering 100 flower tree weight index clusters1) (a) 19982) 1. Unthinnec i 75.3 22.3 148 1.6 2. Hand thin ned 60.7 19.8 149 1.6 3. BA 50 ppm 74.6 22.4 134 1.5 4. 100 77.6 24.8 146 1.6 5. 200 77.8 24.5 142 1.8 6. carbaryl 188 ppm 62.9 21.6 156 1.4 7. 375 77.4 22.4 134 1.3 8. 750 78.3 23.9 139 1.8 9. mixture 3 + 6 78.8 24.7 141 2.0 0. 3 + 7 76.1 24.4 142 2.4 1. 3 + 8 58.7 20.6 150 2.6 2. mixture 4 + 6 73.0 22.7 136 2.5 3. 4 + 7 82.3 25.8 135 1.9 4. 4 + 8 80.6 23.9 156 2.3 5. mixture 5+ 6 64.5 23.1 157 3.4 6. 5+ 7 57.4 19.9 174 4.3 7, 5+ 8 58.8 18.6 143 4.4 SDo.oi 19.6 24 1.2 -test * * »ifferences in 1 column greater than the appropriate LSD-value are significant 2 3 =0.05) . ') after correction for differences in flower clusters/tree ) scale 1 = no till = abundant flowering.
27 A.R. 1997 Fruit Research Statioi
In the second trial, attention was focussed on concentration. At one timing, 12.8 mn average fruit diameter on the old wood, three concentrations of BA (50, 100, and 20( ppm) and of carbaryi (188, 375, and 750 ppm) and all combinations were sprayed Unthinned and hand thinned trees served as controls. The trial was carried out in thi same orchard and in the same way as the former trial. Table 21 gives some results Given the number of fruits per 100 flower treatment thinned. However, in fruits pe tree the mixture 200 ppm BA + 375 ppm carbaryi clusters no treatments thinne* significantly and the same came out the analysis of average fruit weight. Given th< results of the first trial, a later application time might have been more successfull Further analysis showed that addition of BA to carbaryi may enhance the thinnini effect of the latter. In 1998, all trees were in an off-year, only treatments 15, 16 am 17 flowered significantly more than unthinned trees. This means that 200 ppm BA plu one of the three carbaryi concentrations promoted flower-bud formation, but this effec was not sufficient. So, it seems that combining the two thinning agents offers more possibilities fo thinning than using the compounds apart.
Auxin-conjugates
S.J. Wertheim and J.M.T. Balkhoven-Baart
Apple The known thinners naphthylacetic acid (NAA) and its amide (NAAm) are variable ii effect and NAAm is also a mild thinner. Possibly, these effects ars caused by insuffi cient uptake of these polar regulators by the waxy cuticles of the leaves. If this wer true reducing the polarity might enhance uptake and thinning action. This can b achieved by esterification of the molecules. The AB-DLO institute at Wageningen mad three esters: a methyl and ethyl ester of NAA and a methyl ester of NAAm and thes< were evaluated as thinners. On Elstar and Jonagored, 10, 25, and 50 ppm of botl NAA-esters and 10 and 25 ppm of NAA-methyl were applied at full bloom or at the 1( mm fruit diameter stage (old wood). The 50 ppm NAAm-methyl could not be appliei due to shortage in material. Unthinned and hand-thinned trees served as controls as dii trees sprayed with 10 ppm pure NAA at both timings.
The trial with Elstar was carried out in the same orchard and in the same way as botl before-mentioned trials. NAA did not thin at either moment. NAA-ethyl at 50 ppn applied at full bloom thinned with a good effect on fruit size, but without any effect oi flower-bud foramtion. After flowering only 10 ppm NAA-mehtyl thinned but withou effects on fruit size or flower-bud formation. Regression analysis showed that NAA ethyl applied at full bloom thinned linearly more the higher the concentration. Fruit size too, increased linearly with concentration. For NAA-methyl after flowering, sucl relations were not found. NAAm-methyl did not thin, but perhaps concentrations wen too low. The molecule resembles the carbaryi molecule and with that compoun thinning starts at higher concentrations. Future experiments should therfore compris higher dosages.
28 A.R. 1997 Fruit Research Station rhe Jonagored trial was carried in an orchard in the middle of the country on trees on vi.9 in their eighth leaf planted at 3.25 x 1.25 m. The same 20 treatments were ;ompared as in the Elstar trial with seven to eight replicates of one tree per plot. Here, 10 ppm NAA-ethyl and 50 ppm NAA-methyl applied at 10 mm fruitlet diameter thinned ignificantly. Regression analysis indicated that NAA-methyl, applied at full bloom or at he 10 mm stage, thinned linearly more the higher the concentration, but only with the loom applications fruit weight increased linearly. With NAA-ethyl a linear thinning ffect was only present with the post-bloom sprays, but without any effect on fruit ize. In 1998, trees flowered fairly well and only the treatment with 50 ppm NAA-ethyl it 10 mm had a significant higher flowering index than unthinned controls (7.7 as igainst 5.2; LSD001 = 1.6).
>o, it seems that NAA-esters may have more effects than pure NAA. Given the lack of ffect op 10 mm sprays on fruit size, future trials should perhaps aim at timings >etween this stage and full bloom. The latter is unpopular with growers, because fruit et can not yet be judged. For, NAAm-methyl higher concentrations than used here leed to be evaluated.
Chemical thinning of pear
.J. Wertheim
Several thinning compounds were tested on trees of Conference on Quince MC in their enth leaf. Unthinned and hand thinned trees served as controls. Chemical treatments vere: 1, 2, or 3% ammonium thiosulphate (ATS) at full bloom and 16 or 32 ppm NAA
'able 22. Results thinninq trial Conference 137-Ex9719 'reatment Stage Fruits/ Kg/ Fruit Flowering 100 flower tree weight index clusters1) (a) 19982) 1. Unthinned 130.4 29.7 172 5.8 2. Hand thinned 11/06 101.0 25.3 186 6.5 3.1% ATS full 122.3 28.1 173 5.4 4. 2% ATS bloom 109.2 30.9 186 6.4 5. 3% ATS 90.5 25.3 201 5.1 6. 16 ppm NAA + end of 120.7 28.4 177 5.9 7. 32 ppm NAA+ + bloom 97.4 25.2 194 5.5 8. 10 ppm NAA 9.8 mm 103.8 25.0 175 6.3 9. 50 ppm BA 9.8 mm 125.0 29.1 182 5.8 0. 100 ppm BA 105.0 27.3 187 5.8
•SD005 18.3 16 nc :-test * * * * * ns )ifferences within 1 column greater than the appropriate LSD-value are significant P= 0.05) . + = plus 6 mg/l urea. + + = ditto with 8 mg/l urea. 1) after correction for ifferences in flower clusters/tree. 2) scale 1 = no till 9 = abundant flowering.
29 A.R. 1997 Fruit Research Statior
(12 days after full bloom) or 10 ppm NAA, 50 or 100 ppm BA four weeks after ful bloom.At that time fruitlet diameter was 9.8 mm. The NAA applied at 12 days after ful bloom was mixed with urea, the later NAA was not. The ten treatments (Table 22 were compared in eight replicates with one tree per plot. Five treatments caused simila thinning as the hand-thinned control.
These were: 2 and 3% ATS at full bloom, 32 ppm NAA +urea at the end of flowerinc and 10 ppm NAA and 100 ppm BA at 9.8 mm. Of these only 3% ATS and 32 pprr NAA + urea gave larger pears. The ATS, especially 3%, damaged flowers and leaves which is a serious drawback for reasons of landscape. So, it is surprising that 3% ATS promoted fruit growth. NAA applied late did not do so in spite of similar thinnig, but a that time NAA is a known growth inhibitor. In 1998, trees flowered reasonably well bu there were no treatment effects. For the phytotoxic ATS this is again surprising.
International thinning trial with Elstar
J.M.T. Balkhoven-Baart
An international Eufrin thinning trial (137-Ex97018) was carried out in a practica orchard on five-year-old Elstar on M.9. The trial was carried out in 8 one-tree replicates Next to untreated and hand thinned trees, two concentrations of D4017 (BA) plui 0.1 % Tween 20 at 11 mm fruit diameter older wood (23 May), three concentrations o ATS (ammoniumthiosulphate) at full bloom (3 May) and two concentrations of P(8°A NAA plus 3% urea) were sprayed three days after the end of bloom (15 May). Othe treatments (table 23) were 0.025% Ethrel-A beginning of bloom (1 May), 0.075°/« Amid-Thin (63 ppm NAAm) end of bloom (15 May), 0.075% Amid-Thin plus 0.0250/4 Ethrel-A (15 May) sprayed as a tankmix followed by 0.025% Ethrel-A two weeks late (30 May), Sevin SL (750 ppm carbaryl) at 11 mm fruit diameter older wood (23 May and the combination of first Amid-Thin (15 May) and later Sevin SL (23 May). At the beginning of bloom the weather was good but later it became cold. Fruit set wai good, June drop moderate. On 1 July 112 fruits per tree were hand thinned. Chemical ly thinned trees were not hand thinned. All treatments except Sevin SL (treatment 13) thinned compared with untreated. Fruit of unthinned trees were too small. Only 12.7 kg of the total production of 28.0 kg pe tree were 70 mm or larger. Hand-thinned trees had 20.3 kg good sized fruits. Hand thinned, 0.188% D4017, 1.5% ATS and Amid-thin followed by Sevin SL gave best yh< fruit weight. Total production of these treatments was lower. As was found in previou trials D4017 reduced fruit colour despite the good thinning effect. All treatments whicl did not thin or did not thin enough resulted in badly coloured fruits. Although Sevin SI did not thin, it improved fruit size. None of the treatments caused skin russet.
Seed counts For seed counts samples of 10 fruits per tree of the older wood were taken of eacl replicate of the first 9 treatments. Fruits of untreated trees had 1.0 flat and 5.5 gooi seeds. The number of good seeds was lower after spraying with 0.5% and 1.5% AT! and the highest concentration of P. No differences were found in the number of fla
30 A.R. 1997 Fruit Research Station
:eeds. The total of flat seeds plus good seeds was lower with all concentrations of MS and the highest concentration of P. Only fruits of 1.5% ATS showed a slight nalformation of the fruit shape. fable 23. Results of a thinning trial with Elstar 137-Ex97018 Treatment Fruits/ Fruit- Kg/ Flowering 100 flower- weight tree index clusters 1) Jal 19982) Untreated 71 d 124 a 28.0b 2.6a Handthinned 42 a 161 de 22.1a 5.1a- e
0.094% D4017 56 be 149 b-e 26.1a b 6.0b- f 0.188% D4017 47 ab 159 ede 23.0a b 6.3b- f
0.5% ATS 3) 56 bc 148 b-e 26.2a b 4.8a- d 1.0% ATS 49 ab 158 ede 24.5a b 6.9c- f 1.5% ATS 42 a 160 ede 22.0a 7.7e f
?. 0.02% Middel P 57 bc 144 bc 26.5a b 4.0a b 0.04% Middel P 51 abc 149 b-e 24.9a b 5.0a- e
0. 0.025% Ethrel-A (E) 54 abc 146 bed 25.1 ab 4.4 abc 1. (0.075% Amid-Thin + 0.025% E) + 0.025% E. 49a b 146be d 21.5a 8.0f 2. 0.075% Amid-Thin 57b c 141a b 25.6a b 4.0a b 3. 0.156% Sevin SL 62c d 145b c 26.3a b 4.6a- d 4. 12 + 13 46a b 164e 22.9a b 7.3de f
-SDo.01 12 17 5.5 2.7 test ) corrected for differences in bloom spring 1997. 1 =none, 3 = light, 5 = average, 7= good en 9 = very good bloom ) ATS plus 0.1 % Tween 20 leturn bloom )nly the best thinned chemical treatments (0.188% D4017, 1.5% ATS and Amid-thin ollowed by Sevin SL) had enough flower clusters in spring 1998. Although hand- hinning resulted in a good fruit quality in 1997, it was carried out too late to promote eturn bloom. Despite the poor thinning effects, Amid-Thin plus Ethrel and later nother Ethrel spray (treatment 11) improved return bloom most effectively.
'iming, concentration and combinations of ATS on Elstar (137-Ex97021) ~\ the same orchard as the trial described above, a trial was carried out in which timing, oncentrations and combinations of ATS and NAAm were tested (Table 24). Full bloom f the older wood was on 3 May, of the one-year-old wood on 10 May. On 1 July three if the seven replicates were also hand-thinned. This hand-thinning did not interact with
31 A.R. 1997 Fruit Research Statior the thinning results of the treatments. In table 25 results are averages of all seven replicates.
Table 24. Treatments in a thinning trial with Elstar 137-Ex97021 1. Untreated 2. 1.0% ATS1) full bloom old wood+ 63 dpm NAAm (=0.075% Amid-Thin) end of bloom 3. 63 dpm NAAm (= 0.075% Amid-Thin) end of bloom, 15 May 4. 1.0% ATS full bloom old wood, 3 May 5. 1.0% ATS full bloom one-year-old wood, 10 May 6. 2x 1.0% ATS full bloom old wood and full bloom one-year-old wood 7. 2x 0.5% ATS full bloom old wood and full bloom one-year-old wood 8. 3x 0.33% ATS begin bloom (1 May), full bloom old wood and one-year-old wood ^ ATS always plus 0.1 % Tween 20
Sufficient thinning effect was caused by 1.0% ATS on the older wood (treatment 6) or two sprays of 0.5% ATS (treatment 7). Fruit size from one spray of 1.0% ATS did not show sufficient improvement. 1.0% ATS sprayed at full bloom on the one-year-old wood (treatment 5) appeared to be too late. With this treatment fruit size, colour and return bloom lagged behind. The treatments of 0.33% ATS and 0.075% Amid-Thin reduced insufficient thinning, but promoted return bloom. Two treatments of 1.0% ATS (treatment 6) caused over thinning and fruit skin russet. 1.0% ATS followed by 0.075% Amid-Thin (treatment 2)also over thinned. Treatments 2 and 6 resulted in the best return bloom.
Table 25. Results of a thinning trial with Elstar 137-Ex97021 Treatment Fruits/100 Fruit Kg/ Flowerim flower clusters1) weight (g) tree index2) 1. 91 d 138 a 27.8 c 2.9 a 2. 42 a 174 c 19.3 a 7.6 c 3. 68 be 141 a 24.1 be 6.1 be 4. 59 b 150 ab 21.9 ab 5.7 b 5. 76 c 145 ab 24.6 bc 3.1 a 6. 44 a 165 bc 19.0 a 7.4 be 7. 61 b 161 bc 24.2 bc 5.7 b 8. 60 b 149 ab 22.3 ab 6.0 be
LSD005 14 21 4.3 1.8 F-test * * * * * * * * * 1) corrected for differences in bloom spring 1997 2) index 1-9; 1=non e and 9 = many buds on the old wood (27 March 1998)
All ATS-treatments sprayed at full bloom on older wood had less seeds per fruit. Untreated fruits had 5.5 good seeds. Fruits of ATS sprayed trees had one seed per frui less. Severe malformation of the fruit shape was not found. A reduction of the seed
32 A.R. 1997 Fruit Research Station lumber from 3 to 2 seeds per tree could lead to severe malformation of the fruit shape md result in smaller fruits. The effect of ATS on the seed number may have been :aused by the stopping of the pollen tube growth when ATS caused drying out of the item and pistels.
Jelblush - Tentation®
I.M.T. Balkhoven-Baart
îussetting control 152-Ra97011 n 1996 a lot of russet was found on the new apple cultivar Delblush. In 1997 a trial with several GA4+7-treatments was carried out to test when and how russet can be >revented (table 23). The trial was carried out in Randwijk on two-year-old very well eathered trees on rootstock M.9. The trial was carried out with 8 one-tree replicates. fable 26. Treatments 152-Ra97011 untreated l-x 5 ppm GA4+7 (0.5 l/ha) starting end of bloom, every 10 days 1-x 10 ppm GA4+7(1.0 l/ha) starting end of bloom, every 10 days l-x 10 ppm GA4+7 (1.0 l/ha) starting mid-June, every 10 days l-x 10 ppm GA4+7(1.0 l/ha) starting mid-July, every 10 days l-x 10 ppm GA„^(1.0 l/ha) starting mid-August, every 10 days fable 27. Results of a russet control trial with 152-Ra97011 Treatment Fruits/100 Fruits/ Kg/ Fruit- Russeting % kg flower tree tree weight index3) class I clusters1) (gjf) 4) I. 47a 64a 9.6a 152a 341c 77a 1. 58a 63a 10.0a 158a 304a 84a 1. 49a 62a 9.6a 154a 310a b 84a I-. 51a 67a 10.3a 155a 330b c 80a j. 56a 72a 10.6a 152a 336c 76a 3. 49a 60a 9.1a 151a 338c 78a
-SDo.05 nc nc nc nc 23 nc :-test ns ns ns ns ** ns inclusive handthinned fruits and corrected for differences in bloom corrected for differences in number of fruits per tree. russeting index = (%smooth)*1 +(%light)*3 + (%average)*5 + (%serious)*7 + (%very serious )*9 smooth + light russeted fruits
A-treatments had no effect on fruit set (fruits per 100 flower clusters. Table 27), nor >n the number of fruits and kg per tree. The number of fruits had a significant effect on
33 A.R. 1997 Fruit Research Statior fruit weight (P= 0.034) . After correction for differences in fruits per tree there were n( effects from the treatments on the fruit weight. Shortly after harvest fruits were gradée with regard to russet. Best russet control was achieved after spraying 5 or 10 ppm G/ starting end of bloom (treatments 2 and 3). Starting the GA-sprays in mid-June had th< same result as 10 ppm starting at the end of bloom but was not better than untreated At harvest it was clear that large fruits had less russet than small fruits. Indeed then was a significant effect of fruit weight on russet index (P= 0.041) . Correction of russe index with fruit weight did not result in significant effects of the treatments or russeting. Therefore table 27 shows the uncorrected russet index. The trial shows tha russet control with GA on Delblush is not different from russet control in other culti vars. Four 5 ppm GA4+7-sprays starting at the end of bloom seem sufficient. None o the treatments reduced flower bud formation.
Evaluation of Top Fruit Cultivars
The pollination of pome and stone fruit
H. Kemp and M.C.A. van Dieren
Germination of pollen
During the blossom period, pollen of 12 pear and 33 apple cultivars was sampled in th< experimental orchard at Wilhelminadorp. The weather conditions were rather gooc during sampling. Directly after the sampling the pollen was kept in tubes and stored it a refrigerator at 1-2 °C and a rather high relative humidity. One or two weeks, later the rate of germination was examined. The pollen was brought into a droplet of deminerali zed water containing 15% sugar on an object glass. After circa one day at 20-24 °C the amount of germinated pollen (pollen tube longer than 1-2 times the grain diameter was counted under the microscope. The test was run with three replicates of eacl cultivar. The average germination percentages are given in Table 28. The germination rate seemed to be negatively influenced by the (too) high relativ« humidity in the refrigerator, however the differences between the cultivars were large None of the triploid cultivars of apple and pear came up to more than 5% germination The percentage germination of the mutants of Conference (Boonman and Saels I) anc Doyenné du Comice (H17/H19 and Rocobo) was low, lower than the percentage germination of the mother cultivars. Maybe, in the case of the fruit size mutant Saels the low percentage of germination was connected to the deviated ploidy level. Perhaps this also holds for the fruit size mutant Perico (Gieser Wildeman), which because o that cannot be recommended as pollinator. Within the group of diploid apple cultivars the ornamental cultivars surprised positively with 36, 40 and 50% germination (Table 28). Angold (free pollinated Antonovka x Golden Delicious) reached the same level oj germination. The germination of Creston, Delblush, Ecolette, Résista and Santana wa: disappointing. The relatively good percentage of germination of Delcorf and its mutant: (Table 28) is contrary to the sometimes disappointing fruit set in practice in case:
34 A.R. 1997 Fruit Research Station vhere these are used as pollinizors. The results in Table 28, especially the low germina- ion percentages, should not be interpreted too strictly, because pollen was sampled rom trees of varying age and different plots resulting in blossoms that differed greatly quality. The tests will be repeated in 1998. able 28. Pollen germination (%) of apple and pear in vitro in May 1997. lultiyar Germination Cultivar Germination pple dkmene 14 Elstar Fleuren 2 mgold 37 FAW 5878 12 vnwa 11 Golden Delicious 10 iaugêne 36 Golden Hornet 40 iraeburn 41 H 1254 18 :ox's Orange Pippin 12 Jonagold 1 :PRO 80105-75 15 Jonagold Fleuren 5 Ireston (8M-15-10) 2 Karmijn de S. 3 »alili 9 Malus Gorgeous 50 »elblush 4 Monidel 10 »elcorf 38 Red Elstar 16 lelcorf Eversdijk 41 Résista 6 »iscovery 13 Rode Boskoop S.H. 4 colette 5 Santana 1 Ian 13 Topaz 28 lise 17 Yataka 17 Istar 14 ear lonference 31 D. du C. H17/H19 6 lonf. Boonman 0 Orcas 26 lonf. Saels I 0 Perico 4 »elbuena 12 Rocobo 4 lolacomi 9 Saint Rémy 1 lovenné du Comice 31 Verdi 3
Crossings
ach year, hand crossings were made with pollen of apple, pear and plum cultivars to tudy the amount of fruit set of certain combinations of (new) cultivars. In 1997, rossings were made with apple, pear and plum at Wilhelminadorp. The results are ummarized in Table 29. Per crossing 100 (sometimes 80) flowers were used: Five ranches (sometimes four) with ten clusters and two flowers per cluster. After pollinati- n, the stigmas were directly covered with vaseline. In general in 1997, flowering was arly and many cold and windy days occurred (especially after the pollination of pear nd plum) and some nights with spring frosts. The afternoon temperatures during ollination were often rather low (11-18 °C).
35 A.R. 1997 Fruit Research Statioi
Table 29. Fruit set (%) and good seeds/fruit (number at harvest) from hand-madi crossinqs at harvest Pollinated cultivar Pollinizer Fruit set ') Good seeds/frui apple Braeburn Delblush 6 4.2 CPRO 80105-75 Delblush 24 5.3 CPRO 80105-75 Elise 26 4.3 CPRO 80105-75 Elstar 4 4.3 Delblush Delblush 5 1.0 Delblush Delcorf 19 2.5 Golden Delicious Delblush 23 1.5 Jonagold Delblush 23 1.5 Jonagold Topaz 11 1.2 Jonagold Santana 9 2.2 Rode Boskoop Delblush 0 - 2) Rode Boskoop Santana 1 1.0 Rode Boskoop Topaz 0 — Santana Delcorf 9 4.3 Santana Elstar 13 5.6 Santana Golden Hornet 10 7.1 Santana Malus Gorgeous 16 6.1 Topaz Delcorf 2 7.0 Topaz Elise 0 — Topaz Elstar 0 — Topaz Golden Hornet 2 3.5 pear Beurré A. Lucas Verdi 0 — Orcas Conference 0 — Orcas Conference Saels I 0 — Orcas Gieser Wildeman 0 — Orcas Orcas 0 — Orcas Perico 0 — Triomphe de Vienne Verdi 0 — plum Vovaqeur Excalibur 2 — 1) Fruit set at harvest 2) — = irrelevant/not counted
Apple fruit set varied between the cultivars from none to good, mainly depending oi date of crossing and night frost. Self-pollination with Delblush resulted in 5% fruit set in 1995 in 3%. As with Golden Delicious, Delblush seems to be somewhat self-fertile Contrary to earlier findings, crossings with Delblush resulted in good fruit set o Golden Delicious and Jonagold. Delblush induced poor fruit set with Braeburn. Th flowering period overlapped sufficiently. The scab resistant cultivars Santana and Topa gave only moderate fruit set on Jonagold, this may be partly due to spring frosts These crossings have to be repeated next year. Both cultivars started flowering one t
36 A.R. 1997 Fruit Research Station i few days before Jonagold. The combination Delblush and Delcorf can be practised, considering the percentage fruit set (Table 29) and the flowering period of both :ultivars. rhe new CPRO selection 80105-75 gave good fruit set with pollen of Delblush and [lise, but not with pollen of Elstar. Considering the crossing parents, it could be that )oth cultivars have the same S-alleles. CPRO 80105-75 is a late flowering cultivar. )elcorf, Elstar, Golden Hornet and Malus Gorgeous gave moderate fruit set on Santana. However, both the latter mentioned ornamental apple cultivars gave many seeds per ruit (Table 29). Perhaps, the percentages of fruit set were also negatively influenced >y spring frosts. The flowering period of the five cultivars had sufficient overlap for nutual fruit set. Presumably, the poor fruit set of Rode Boskoop and Topaz was also a esult of the spring frosts (Table 29).
The several crossings with pear cultivars were a complete failure due to spring frosts luring the flowering period. The plum cultivar Excalibur flowered rather early and the :ultivar Voyageur rather late; the overlap was just sufficient. Presumably due to bad veather conditions during the flowering period, the fruit set of these plum cultivars was rery poor (Table 29).
:itting of apple cultivars in sustainable production systems & cultivar esting with apple
/. Kemp and M.C.A. van Dieren
"ultivar testing at Wilhelminadorp/Randwijk n the spring of 1997, 90 cultivars, including 25 standard cultivars, were planted at Randwijk. At the same time 10 apple cultivars and mutants were planted in a greater lumber of trees intended for storage research. This research had already been started i. 1996 (see also page 83: Storage). The owners of some 30 new cultivars claim that hese cultivars are not, or not very, susceptible to scab. Most of these cultivars iriginate from the Czech Republic, France, Switzerland and Poland. Practically all ultivars were planted in one plot with, and in one plot without, fungicide application. Jearly all cultivars stood on the M.9 rootstock. In the winter of 1997/1998, 38 ultivars were grubbed for different reasons (Table 30). Rejected cultivars are not ecessarily inferior cultivars, because on many occasions they were grubbed because hey were no better than the current assortment in The Netherlands.
»uring the summer, the trees in the plot without fungicide application were assessed or incidence of scab and powdery mildew. At harvest, the fruits were screened for cab incidence and severity. Some of the results are given in Table 31.
i 1997, weather conditions were favourable for the scab fungus and some heavy scab
37 A.R. 1997 Fruit Research Statio
Table 30. Data of apple cultivars grubbed in winter 1997/98 at Wilhelminadorp. Cultivar Origin Planted Characteristics Eating Others quality M 21-69 Germany 1994 m large ribbed fruit, waxy skin, short shelf-life, susceptible to scab 11W-12-11 Canada 1996 mg small fruit, sometimes rotting due to small cracks, relatively good shelf-life, early ripening A 933/190 England 1996 m waxy skin, acid Ahra * Germany 1994 mg susceptible to bitter pit, mouldy core, pre-harvest fruit drop, Ahrista * Germany 1994 severe fruit tree canker, large mouldy core, pale green ground colour, ribbe fruit, waxy skin Auriu de BistritaRumania 1995 mg waxy skin ornamental cultivar, very susceptible Baugêne * France 1996 to fruit tree canker, dark red fruit mg firmness good, fast break down, shon BN 26/261 * Rumania 1995 fruit stalk m short firm fruit stalk, flat fruit, fast BN 32/41 * Rumania 1995 break-down of the fruits rg = Delcorf Schuhmann, more blush Celeste Germany 1994 than standard, some chimaeras, moderately waxy skin, autumn cultiva Cox's Van Bemmel Netherl. 1995 mg much brown to dark red blush, some chimaeras, short fruit stalk CPRO 88022-A-13 Netherl. 1996 mg unattractive grey-green fruit with a purple red blush, cracks near the stalk attachment Cwastresse Double * Belgium 1994 mg large flat unattractive ribbed fruit, early fruit drop, susceptible to bitter pit, firmness good, short shelf-life D:0106 Sweden 1995 m acid, short fruit stalk, autumn cultivar DCABO 81.417.016 * Italy 1996 m some chimaeras, large core, ribbed, autumn cultivar DCABO 81.417.016 * Italy 1996 m rather small fruit, some chimaeras, large core, acid, autumn cultivar Delearly France 1995 m rather small fruit, productive, autumn cultivar, distinctive aroma, susceptlbk to scab
38 A.R. 1997 Fruit Research Station
)elgobel France 1995 mg waxy skin, somewhat insipid )eloran France 1995 m waxy skin, short shelf-life, large calyx cavity, autumn cultivar, susceptible to scab )enar Czech Rep. 1994 m short shelf-life, long fruit stalk I55/52 England 1993 m late ripening cultivar, firmness good, susceptible to bitter pit and scab AW7167 * Switzerl. 1995 mg small fruit, mouldy core, fast break down arka Czech Rep. 1995 mg waxy skin, some chimaeras, insipid, susceptible to scab [atka * Czech Rep. 1995 mg bitter pit already shown before harvest, waxy skin, core browning, flat fruit rtarina Switzerl. 1994 m susceptible to scab and powdery mildew flat fruit /lcShay * USA 1995 m large core, smooth bedewed skin, soft flesh, fast break down, some chimaeras, productive, late ripening IPV-1 Netherl. 1993 productive, late ripening IY 632 USA 1995 m large fruit, considerable loss of firmness during storage, late ripening, susceptible to scab, IY 65707-19 *USA 1995 m short shelf-life, early fruit drop, some chimaeras IY 75441-67 *USA 1995 m firmness good, waxy skin X 9176 * France 1996 mg attractive fruit, short fruit stalk einette de lenheim * England 1994 m large flat fruit, waxy skin, susceptible to bitter pit, short shelf-life, early fruit drop hampion Slovakia 1995 m productive, tree easy to train, some chimaeras, moderately waxy skin, so mewhat insipid, susceptible to scab lovakia Slovakia 1995 mg waxy skin, deep stalk cavity 4982 * France 1994 m susceptible to powdery mildew, firmness good, insi pid, ribbed 6690* France 1996 mg waxy skin luzana * Czech Rep. 1995 m crisp, very short fruit stalk, acid, short shelf-life m = moderate; mg = moderate to good; rg = rather good ultivar names followed by an asterisk (*) are (highly) scab resistant
39 A.R. 1997 Fruit Research Statioi infections occurred. As in 1996, on average, powdery mildew attack was severe (Tabl< 2). Some scab on leaves and fruit was seen on 25 cultivars/selections being claimed ti have Vf scab resistance. This outnumbered the amount of scabbed cultivars/selection in previous years by far. Also the scab symptoms on some of these 'resistant' cultivar (among others Otava and Santana) were more severe yhan in previous years. Neverthe less, some cultivars with Vf-resistance (Fiorina, Sir Prize and CLR 13T45), eve standing beside scabbed trees, were still free from scab. Discovery, normally not muc susceptible to scab, had also a lot of fruit scab and this was even higher than on Elstai Presumably, the timing of the heavy scab infection periods in relation to the develop ment of the fruit was of importance for the resulting scab incidence. In 1997, Alkmen and Belle de Boskoop also had less incidence of fruit scab than Discovery (Table 31! only the leaf scab incidence on Discovery was lower. The fruit scab incidence o Santana equalled that on Elstar, but the leaf incidence of scab on Santana was lowei At the end of the season, leaf scab, but not fruit scab, occurred on the cultivar Topaz.
Table 31. Rating 1) for incidence of scab (at harvest) and powdery mildew (June August) in 1997 at Wilhelminadorp. Cultivar Years without Scab Powdery mildev funqicides on fruit on leaf + shoot Cultivars susceptible to scab Alkmene 8 3 2.5 Braeburn 4 5 2.5 Cox's Orange Pippin 8 3 6.5 Delblush 2 9 2 Discovery 8 6 <1 Elise 8 4 2 Elstar 8 5 6.5 Gala (Regal Prince) 7 9 3 Golden Delicious 8 9 5 Jonagold 5 7 6 Rode Boskoop 8 4 2.5 Cultivars resistant to scab Ahrista 4 2 5.5 CPRO 84015-17 5 <1 2 Delorina 6 2 5.5 Ecolette 8 2 1 Fiorina 8 0 5 Gerlinde 4 4 7 GoldRush 4 1 7.5 Prima 8 2 1.5 Priscilla 8 2 4 Santana 8 5 7 Topaz 3 0 2 0 = no incidence; 1 = low incidence; 9 = high incidence
40 A.R. 1997 Fruit Research Station n 1997, it was striking that the incidence of scab on the cultivars/selections Delvale, loseph Musch, La Paix, Angold, Radoux, Reinette de Blenheim, Beemsterherfst, Ukmene, NPV-1 and Pirina and the ornamental cultivars Golden Hornet and Malus Sorgeous was rather low. The chances are that in the coming years some fungicide prays will be applied at times when heavy scab infection periods occur, to minimize he risk of a breakthrough in the Vf-resistance.
Severe to very severe powdery mildew incidence occurred on Goldrush, CPRO 80105- 5, Gerlinde, Marina and Santana, moderate to severe powdery mildew incidence ccurred on 11W-12-85, CLR 13T45, Cox's Orange Pippin, Elstar, Jonagold and [4982. In 1996, Goldrush, Santana, Marina, X4982 and CPRO 80105-75 also had a )t of powdery mildew, and the incidence was as much as or more than that of the ultivar Elstar. In 1997, it was striking that very little mildew was seen on Discovery, >enar, Shampion, Beemsterherfst, Delgollune, Yataka, Ecolette, Malus Golden Hornet, arka, BM 55180, D: 0106, Delvale, Joseph Musch, Radoux, Cwastresse Double and leinette de Blenheim. able 32. Taste tests with early autumn cultivars and scab resistant cultivars in autumn 1997 at Wilhelminadorp ultivar Taste score ') 9 September 29 October 5 November 26 November leleary 6.3 a •elcorf 6.1 ab ristine * 5.7 bc PRO 81001-33 5.5 cd irina 5.3 cd 1W-12-85 5.1 d :ed Elstar 6.6 a 6.5 a antana * 6.3 a 6.2 a 6.6 a N 36/152 * 5.7 b ihra * 5.6 b AW 7207b * 5.4 bc X 9176 * 5.0 c opaz * 5.9 ab 5.5 b 'iktoria * 5.6 b esista * 5.5 b AW 7313 * 5.6 b o-op 37 * 5.2 bc AW 7167 * 4.8 c PRO 87057-34 4.7 c 1 = very poor taste to 9 = excellent taste. :ultivars followed by an asterisk (*) are scab resistant.
1997, a severe to very severe incidence of fruit tree canker was observed in the ultivars/selections Baugêne (ornamental cultivar), Ahrista, Cwastresse Double, SPAB
41 A.R. 1997 Fruit Research Statior
919, Discovery, Rode Boskoop S.H., Pristine and Co-op 37. The incidence in the cultivars/selections SPAB 921, CPRO 83016-21, Pingo, Pirina and X4982 was modéra te to severe. The observations up untill 1996/1997 are summarized in the weekly magazine Fruitteelt 88(1998)15:13-15 andi n Acta Horticulturae Nr.484.
Table 33. Taste tests with apple cultivars in winter 1997/1998 at Wilhelminadorp. Cultivar Taste score ') 14-10 22-10 12-11 19-11 12-01 19-01 23-01 26-01 27-01 87031-47T) 6.9 a — ... — ...... — — 87031-54T) 6.0 b ...... Red Elstar 5.9 b 6.8 a 6.2 a 6.1 a ... — 6.4 a ... 6.1 b 83016-21T) 5.8 b ...... —5.4 b — — 80107-59T) 5.4 be ...... — 81013-14T) 5.0 c ... — ... — — — BM 47854 ... 6.3 ab ...... 5.9 ab BM 55180 — 6.3 b — ...... — — ... H 1254 ... 5.5 c — ...... — ...... KDH 8515 — 5.4 c — ... — — — — — Jonagold ...... 6.4 a — 5.5 be — — ... — Chevadel ...... 6.2 ab ...... — 5.3 c Delaf ... — 5.6 b — ...... — ... Delvale — ... 4.9 c ... — ... — ...... 87035/66T) — ... — 6.3 a ...... FAW 5878 — ... — 6.3 a ... — ... 6.5 a — 86015-111T) ... — ... 6.3 a ... — 6.2 a — — 80105-75T) — — — 5.9 a — ... 5.5 b — ... 87020-48T) — ... — 5.6 a — ... — — 5.5 c 8M-15-10 — ... — — 6.5 a 6.3 a ...... 6.6 a SPAB 919 ...... — 6.5 a ...... — — Pi-A-16,97 ... — — — 5.7 b — ... 6.4 ab — Hidala ... — — — 5.4 be 5.5 c — ... — NPV-1 — ... — ... 5.1 c — — ... — 8S-27-51 „•- ...... 6.2 ab ... — — Delblush ...... 6.1 ab 6.4 a 6.5 a — Golden Del. — ... — — — 5.7 bc — — — Elise — ...... — — 5.3 c ... — — Iduna — ... — — ...... 5.9 bc ... Topaz * — — — ...... — 5.4 c — Granny Smith — ...... — ...... 4.0 d — FAW 7313 * ...... — — — — ... 5.2 c M 1 = very poor to 9 = excellent taste. Values in one column followed by the sam letter(s) do not differ significantly (P= 0.05) Cultivars followed by an asterisk (*) are scab resistant. T) these cultivars are CPRO-selections
In 1997, scab and powdery mildew assessments were carried out the first time £
42 A.R. 1997 Fruit Research Station
Randwijk. Already quite a lot of scab had been observed on Golden Delicious and ^afzubin (Rubinette) in their first year of growth. Scab was also present on two new :ultivars. On a few of the cultivars with the Vf-resistance, growing for the second year it Randwijk, some fruit scab incidence was observed. On circa 60% of the cultivars, jrowing for their first year at Randwijk, some powdery mildew incidence was observed. n the winter 1997/1998 fourteen taste tests with apple cultivars were performed: One with early autumn cultivars, three with scab resistant cultivars (Table 32) and eight vith (mainly) non-scab resistant cultivars (Table 33). The other two tests were related o a test with large and small, and (un)blushed fruits of Delblush (Tentation®) (see ruitteelt 88(1998)26:9-11) and a split test, performed in co-operation with the NAKB, omprising the testing of apples from Dutch and Belgian origin (see Fruitteelt 58(1998)7:10-11) . In this issue of Fruitteelt the results of an assessment of scab esistant cultivars by 'biological' fruit growers are also presented. With the exception of his test and and the one performed in co-operation with the NAKB, all tests took place it FPO at Wilhelminadorp with 32-35 employees as tasters. The fruits were stored at 1- 5 °C until two to four days before testing and thereafter were exposed to room emperature. All fruits came from the experimental orchard at Wilhelminadorp, except or those of Santana (fruit farm near Wilhelminadorp), Viktoria (Randwijk) and Granny Smith (Florida, USA). The test results are summarized in Table 32 and Table 33.
'able 34. Growth, production and sorting of (Red) Boskoop mutants at Wilhelmi- nadorp (144-WJ9502). /lutant Tree volume Production Fruit weight Fruits > 50% (m2) (kg/tree) (g) blush (%) Autumn199 7 1996-1997 1996-1997 1997 :AW-Q11/E33 0.62 14 281 43 'ellier 1g 0.26 10 254 82 'ellier 2g 0.17 9 282 62 ierr 0.81 20 -290 87 i.S. Hübsch 0.78 21 286 74 ieijnoudt 0.31 12 261 62 'an Bemmel 0.73 20 286 83 lielaar 0.94 18 272 97 :elica (Welbo) 0.86 21 274 96 I. Bosk. SHKL 0.75 15 237 98 Ichone v.B. SP 0.40 11 251 27 'an der Vliet 0.76 16 260 75 iakker 0.85 21 284 60 lode B. S.H. 0.79 18 274 45 Volf 0.85 17 238 70 d the beginning of September, the selection 11W-12-85 was not yet completely ripe nd therefore judged to be too firm and too acid by several tasters. The shape of the ee and the leaf condition of this selection (Summerred x Discovery) were very fine, ut the susceptibility to scab and powdery mildew was strikingly high. Delearly was
43 A.R. 1997 Fruit Research Statio also very susceptible to scab, but the taste was not bad (Table 32). However, due t the moderate size of the fruits, this cultivar is not a replacement for Delcorf (Table 30] Pirina (Pi-A-5,164) is not very susceptible to scab and powdery mildew, but seems no to be a replacement for Delcorf with regard to fruit size, taste and shelf life. Pristine i a very early ripening and scab resistant cultivar and it scored rather well (Table 32). It shelf life was strikingly good for an early summer cultivar.
In general, Santana was appreciated well in October and November (Table 32). Afte some weeks of storage, Santana tasted clearly better than at harvest time. At the time, the fruits were too acid. Meanwhile, Ahra and PX 9176 had been grubbed (Tabl 30), whereas BN 36/152 and FAW 7207b will be further evaluated. Topaz wa appreciated by some of the tasters because of its aroma and crispness, but other found Topaz too acid. Co-op 37 was firm, but scored many times negative for tast (insipid and sloppy). On 26 November, the taste of Santana still scored well, despit the fact that firmness was no longer optimum. At the end of November, FAW 716 and CPRO 87057-34 were already too far broken down (Table 33). Meanwile, FAV 7167 had been grubbed (Table 30).
It is clear that the number of cultivars with good eating quality has increased in recer years (Table 33). Ten new cultivars appeared to be tasty, firm, crisp and juicy. In th next years, futher selection has to be made, based on eating quality and growin properties.
Table 35. Growth, production and fruit weight of Elstar mutants at Zeewolde (144 Ze9506). Mutant Virus Average shoot length Production Average frui status1) (growth , cm) spring (kg/tree) weight (g) 1995 1996 1997 1998 1995-1997 1995-1997 Heines vf 31 16 12 18 11 174 V.d. Plasse vf 32 18 13 17 12 183 Daamen II ? 35 18 12 17 12 170 Bruynzeel II ? 33 18 13 17 10 181 In 't Groen ? 33 16 13 16 14 173 Jacobs vf 33 17 13 17 11 172 PFWII vf 33 18 13 18 12 183 Bel-El nvf 32 17 13 18 11 169 Red Elstar vf 31 17 13 17 12 186 M vf = (presumably) virus free; nvf = (presumably) not virus free
On 14 October, one part of the fruit of CPRO 87031-54 was already too soft, an another part of that of CPRO 80107-59 was still too firm (Table 33). Results of the tes on 12 November pointed to the fact that only 15% of the 33 tasters rated the swee tasting cultivars as good to very good, whereas 45% of the tasters rated the mor neutral (e.g. Jonagold) to sweet-acid (e.g. Elstar) tasting cultivars as good to ver good. However, 25% of the tasters rated the sweet-acid cultivars as 5 or less. In th
44 A.R. 1997 Fruit Research Station
;ase of sweet tasting cultivars this percentage of tasters amounted to 50. Sweet lasting (but not insipid sweet), crispy, juicy apples can really rank a good score, as is demonstrated by the results of the tests on 19 and 27 January (Table 33). On 19 Movember, many tasters assessed CPRO 80105-75 as acid, clearly more acid then Elstar and this was also the case on 23 January. On both 12 and 26 January, Pi-A- 16,97 was rather acid, but during the storage period the taste improved (Table 33). At he end of December, fruit of Granny Smith was obtained direct from the wholesaler nd after one month of storage at 3 °C had a firmness of 4.9 kg/cm2 and a sugar ontent of only 10.0 % brix. On 26 January, upwards of one third of the tasters assessed these fruits (pealed parts without name) as insipid/sloppy and sour/acid. This äste test revealed that some of the tasters assessed Topaz still as too acid.
"lone and mutant trials at Wilhelminadorp
'ox'sOrange Pippin rhe trial (144-Wi9102) with 21 clones, planted in the spring of 1991 (one-year-old naidens on M.9), again produced well in 1997: On average 13 to 18 kg per tree. Also his year. Van Vliet-2 had a low production of hardly 7 kg/tree. In November 1997, the xterior quality (of the fruit in the bins) was assessed in co-operation with employees of hree different auctions and of the NAKB. External financing made possible further esting of the exterior and interior quality of ten mutants (picked at 5 harvest dates). In his testing Queen Cox clones from other trials were incorporated. Production, growth nd quality data obtained up to and including 1996 have been published (Fruitteelt $8(1998)2:7-9).
Data from three clone trials (144-Wi9205, 144-Wi9206 and 144-Wi9207) with Queen "ox that were planted in the spring of 1992, have been inserted in this publication. These trials, comprising of 12 mutants in total, were planted as one-year-old maidens >n rootstock M.9. In 1997, again production of these clones was good, varying from 11 to 18 kg per tree. The production of the self-fertile Queen Cox clones 7 and 18 was ather low: On average 11 to 13 kg per tree. In 1997 also, the fruit size, and as a result he production, of these two self-fertile clones was less than those of the other clones. Jnder the favourable conditions for cross-pollination at the research plots (many ultivars close together), self-fertility negatively affected production and fruit size. Jnder poor cross-pollination conditions this might be different. In 1998, the initial fruit et of the clones will be investigated, to see whether the fruit set of the self-fertile lones is different from the other clones. So far, clone 18 has a higher production per ree and per tree volume than clone 7. Clone 18 is commercially available in England. loskoop i the spring of 1995, a trial (144-9502) was planted with 15 mutants of Boskoop; amongst these the already known new colour mutants Celica (Welbo) and Bielaar. hree mutants had a compact, spurry habit. Six clones came from The Netherlands, six rom Germany, two from France and one from Switzerland. Red Boskoop "Schmitz lübsch" acted as a standard. The mutants from The Netherlands and from Germany Yere also planted in the experimental garden at Horst.
45 A.R. 1997 Fruit Research Statio
One-year-old trees on M.9 were planted at Wilhelminadorp with the following plantin distances: Narrow: 1.00 m (non-spurs) and 0.75 m (spurs) Normal: 1.25 m (non-spurs) and 1.00 m (spurs) Wide : 1.35 m (non-spurs) and 1.20 m (spurs) The distance between the rows is 3.25 meters.
At Wilhelminadorp, the mutants blossomed less well in 1997 than in 1996, but sti moderately to sufficiently well. The spurs blossomed less well yhan the non-spurs. Th production varied from 4 (spurs) to 12 (non-spurs) kg per tree. Table 34 summarize the data on growth, production, fruit size and fruit colour: The differences between th mutants were considerable. Mutant Reijnoudt stayed behind in growth and productior In November 1997, the exterior quality (of the fruit in the bins) was assessed in cc operation with employees of different auctions and of the NAKB. At Horst, the sam was done by employees of the FPO.Again the mutants Bielaar and Celica were rated a good, although the latter was somewhat more striped. Rode Boskoop Herr and Rod Boskoop Van Bemmel were also beautiful. The rating at Horst was similar. Bielaar an Celica are virus-free available from the NAKB.
Clone and mutant trials at Horst, Randwijk and Zeewolde
Jonagold In the spring of 1992, a trial (144-9201) with 13 colour mutants of Jonagold wa planted in the experimental gardens at Horst, Numansdorp and Zeewolde. In winte 1994/1995, the trial was grubbed at Numansdorp, due to the closing down of thi garden, and in winter 1995/1996 at Horst, due to severe incidence of fruit tree canke and economies within the FPO.
Obviously, 1996 was an off-year at Zeewolde, but again in 1997 the production wa good. In 1997, the production per tree varied from 20 to 25 kg and the average fru weight varied from 207 to 241 gram. On average, the virus-free mutants still produce nearly 3 kg per tree more than the virus-infected ones. The average fruit weight wa nearly 225 gram for both groups of mutants.
In 1997, Wilmuta, Novaja, Crowngold, Jonaveld, King 8765 T, Jonagored, SchneicaE Decosta and Jomured were picked five times, and each time the fruits within the tre canopy were separated from those from the outer part of the canopy. For all fru samples among others the amount and intensity of blush, ground colour, sugar, acic firmness, taste, and fruit weight were determined before and after storage. A summar of all these observations will be published
In 1996, a Jonagold mutant trial started at Randwijk. In the spring of 1997, two oth« mutants were added, bringing the total up to eight under trial. A first production WE obtained in 1997. Part of the fruit was subjected to storage research and research o the amount and position of anthocyanin.
46 A.R. 1997 Fruit Research Station
E/star A trial with nine interesting new colour mutants of Elstar was planted in the spring of 1995 at Zeewolde. The trial comprised eight bright red mutants and one dark red mutant: Bel-El (Red Elswout®). Differences in growth and production became more clear in 1997 (Table 35).
Additional financing made it possible to pick all mutants five times and to rate the exterior and interior quality before and after storage of the fruit. The results will be published in due course.
Bos/coop See clone and mutant trials at Wilhelmioadorp.
Fitting of pear cultivars in sustainable production systems & cultivar testing with pear
H. Kemp and M.C.A. van Dieren
Cultivar testing at Wilhelminadorp/Randwijk
In the spring of 1997, 15 new cultivars were planted at Randwijk, including several Norwegian cultivars and two fruit size mutants of Gieser Wildeman. In winter 1997/19- 98, 17 cultivars were no longer under trial (Table 36).
At Wilhelminadorp and Randwijk, every cultivar was tested with ten trees being treated with an application of fungicides and five being without such treatments. On the fungicide-free plots, disease susceptibility was investigated. Nearly all cultivars stay on Quince MC with an interstem (Beurré Hardy, and since 1994 Doyenné du Comice). On 18 of the 70 cultivars under trial on the plot at Wilhelminadorp (unsprayed since 1994), :ruit scab was observed on mainly Verdi and Diana in 1997. The cultivars Doyenné du omice, ISF 84.3336.40, and ISF 80.46.70 were moderately scabbed. In April 1997, again branches and leaves of several cultivars and parcels with scab were brought in, :o increase the amount of inoculum. No inoculum was brought in at Randwijk. In 1997, ome incidence of scab on leaves was present on five out of upwards 50 cultivars at Randwijk.
\X Randwijk, all 40 cultivars were assessed for the amount of second flowering and the ncidence of Pseudomonas. There was much second flowering and a high incidence of Pseudomonas was present on one new cultivar, originating from France. Few second lowering was present on the other cultivars. A high incidence of Pseudomonas was ilso present on the cultivar Delbuena. A rather low incidence of Pseudomonas was »resent on five cultivars, among others Delmoip. The other 14 cultivars showed almost) no Pseudomonas.
47 A.R. 1997 Fruit Research Station
Table 36. Data of pear cultivars grubbed in winter 1997/98 at Wilhelminadorp. Cultivar Origin Planted Characteristics Eating Others Quality ') ISF 80.51.72 Italy 1995 m moderately productive, musk-like taste, short shelf-life, firm fruit stalk ISF 80.66.82 Italy 1994 m coarse fruit ISF 80.108.72 Italy 1995 m fruit stalk on one side ISF 84.3262.40 Italy 1994 m pink-red blush, coarse fruit ISF 84.3336.40 Italy 1994 m very bumpy coarse fruit, short shelf-life BP 9292 Sweden 1993 mg thin fruit stalk, short shelf-life, coarse ribbed fruit BP 9667 Sweden 1993 rg thick-set unattractive fruit with many grit cells, short shelf-life Diana Czech Rep. 1995 m brown-red blush, coarse fruit, very susceptible to scab, smooth skin Erika Czech Rep. 1995 m coarse bumpy fruit Etrusca Italy 1995 m (brown)red blush, short shelf-life, musk-like taste, smooth skin Giolu Italy 1995 m rather short fruit stalk on one side, notable lenticels, red blush, bumpy ribbed fruit HW 614 Canada 1995 m high fruit rot incidence, coarse bumpy fruit HW 616 Canada 1995 mg short firm fruit stalk, short shelf- life, no grit cells HW617 Canada 1995 m very short firm fruit stalk, dark- red blush, uneven ripe, very bumpy HW620 Canada 1995 m short fruit stalk, coarse and very bumpy fruit, no grit cells Nitra Czech Rep. 1994 m big fruit stalk, red blush, notable lenticels, bumpy nattractive fruit Vila Czech Rep. 1995 m firm and often fleshy fruit stalk, pink-red blush, coarse fruit, ma] many grit cells i 1) m = moderate; mg = moderate to good; rg = rather good
Unfeathered trees of Verdi on Quince MC with a Doyenné du Comice interstem, plantée in the spring of 1994, have grown strongly during the past years. The trees directly or Quince MC showed only moderate vigour. In 1997, blossoming and production wert good at Wilhelminadorp and at Zeewolde, but production was poor in Noord-Limburc
48 A.R. 1997 Fruit Research Station
Table 37). At Wilhelminadorp again the flower bud formation for 1998 was good, assessment of the leaf condition of the trees without interstem proved that Verdi leeds an interstem. At Wilhelminadorp, Noord-Limburg and Zeewolde, differences in rowth, vitality, production and fruit weight were great (see also Table 37). In 1997, he total production of three picking times was on average 16.5 kg per tree at Wilhel- inadorp and the average fruit weight amounted to 240 gram. The fruit was well lushed, even the fruit from trees with an interstem. able 37. Production and growth of Verdi on Quince MC in Noord-Limburg and Zeewolde (144-9411). reatment Noord-Limburg Zeewolde Leaf cond.1) Growth Fruits/tree Kg/tree Av. fr. weight (g) 1997 1997 up to 1997 1996-1997 1996-1997 o interstem 3.8 4.9 36 8.7 209 iterstem 6.9 7.5 68 17.8 217 ) assessment on 2 October 1997: 1 = very poor; 9 = very good i winter 1997/1998, four taste tests with pears were performed at FPO-Wilhelmina- orp. The fruits were picked at the experimental garden at Wilhelminadorp and were tored at 21% 02 and 1 °C until six days before testing and afterwards at 18-20 °C. hirty-four employees were involved in taste testing. The results are summarized in able 38. The two cultivars CPRO P. Nude and Orcas were rated as good and compara- le to Conference.
'able 38. Taste tests with pear cultivars in autumn 1997 at Wilhelminadorp lultivar Taste score 'J 20 Oct 3 Nov 17 Nov 1 Dec :PRO P. Nude 6.7 a — — ... inference 6.6 a 6.7 b — 6.7 b Ircas 6.4 ab — ... — »eleté 6.0 bc ...... loyenné du Comice 5.4 c ... 7.3 a 7.6 a 5F 80.09.82 ... 7.2 a — ... P9357 ... 6.0 c ...... ierre Corneille — 5.7 cd — — ,bate Fétel — 5.4 d — ... P 1043 — 4.8 e — ... îgeborg — — 6.3 b — elbuena ... — 6.2 b ... olacomi (Jowil®) — — 6.0 b ... ritjof ... — 4.8 c — erdi + interstem ... — ... 7.4 a onne L. d'Avranches ...... 5.0 c aailinq Driehoek ...... 4.6 c Taste score: 1 = very poor; 9 = very good
49 A.R. 1997 Fruit Research Statio
At the beginning of November 1997, ISF 80.09.82 was rated strikingly good (as i 1996), and was clearly appreciated more than Conference. In the same test, th Swedish selection BP 9357 was appreciated as being less good than Conference. Th cultivars Pierre Corneille and Abate Fétel were rated lower than Conference. Abat Fétel was still (too) firm and Pierre Corneille was somewhat insipid. BP 1043 was firrr dry, insipid and mealy at the same time (Table 38). In mid-November, Ingeborç Delbuena (Peradel®), and Dolacomi (Jowil®) had sufficiently good taste, but not as goo as Doyenné du Comice. Dolacomi and Delbuena were judged to be slightly acid. In th spring of 1998, these two productive, compact growing cultivars will be planted o stronger growth inducing rootstocks at Randwijk to see whether a vigorous growt improves the leaf/fruit ratio and the sugar content in the fruit. The cultivar Fritjof wa (still) too firm. At the beginning of December, the fruit of Doyenné du Comice an Verdi (from trees on interstem) was appreciated strikingly well, both significantly bette than Conference fruit. Bonne Louise d'Avranches and Zaailing Driehoek were both nc sufficiently juicy. Considering the good ratings of Doyenné du Comice in the latte tests, it seems that testing the cultivar on 20 October was too early (Table 38).
Fitting of pium and sweet cherry cultivars in sustainable productioi systems & cultivar testing with plum and sweet cherry
H.Kemp, H. Wustenberghs and M. Balmer
Cultivar testing at Wilhelminadorp/Randwijk
H. Kemp and M.C.A. van Dieren
In 1997, 29 plum cultivars were planted at Randwijk, half of them being standar cultivars for reference to flowering and harvest period and fruit assessments. The ne\ cultivars were also planted at the Fruitteeltcentrum K.U.L. at Rillaar, Belgium. In th winter 1996/1997, the 16 cultivars already planted in 1996 at Randwijk, were tran; planted to the same trial field for plum cultivar testing at Randwijk. At Wilhelminador[ six cultivars were grubbed (Table 39). The results of the plum cultivar trials, teste during the period 1988-1997 in The Netherlands and Belgium, will be summarized i Acta Horticulturae Nr.478. Cultivars suited to growing in practice in The Netherlands are described in Fruitteelt 87(1997)34:16-18. The Swedish cultivar Jubileum gave strikingly good fruit set and production at Wilhelminadorp and at Rillaar, despite ba weather circumstances during flowering (night frost and cold weather).
In 1997, cherry cultivars were planted for the first time at Randwijk. In total 1 cultivars were selected, based on test results from inland and abroad, including th sour cherry cultivars Gerema and Karneol originating from Germany. It is intended t have a collection of cultivar-rootstock combinations of interest for practice as demor stration object and for doing some additional observations.
50 A.R. 1997 Fruit Research Station lultivar trial with sweet cherry at Rillaar, Belgium
/. Wustenberghs and H. Kemp ach year, 10 to 20 new cherry cultivars are being planted at Rillaar. Until 1994, new ultivars were budded on Damit (GM61/1) rootstock, and since then Gisela 5 has been ised. Per cultivar three trees are planted with a planting distance of 4.5 x 2 or 3 rieters. Tree shape: spil. In 1997, almost 120 cultivars were under trial. able 39. Data of plum cultivars1) grubbed in winter 1997/1998 at Wilhelminadorp lultivar Planted Kg/tree Fruit Eating Picking Remarks weight quality period (q) 2) ilisa 1994 1.6 75 g beginning of = (FA)W1/41,hartshaped, September stone cracking,14.9 %brix, dark blue, rather vigorous growth, rather upright älomita 1994 4.2 49 m end of July round, 11.4 %brix, red- blue, vigorous growth, (very) upright, susceptible to spider mites iilvia 1992 7.3 73 mg mid- = Dor,egg-shaped August red/dark-blue, 15.1%brix, (very) vigorous growth, rather upright '72521 1992 20.0 92 2nd week of elliptic/egg-shaped, dark- September blue, 18.6 % brix,hori- zontal hanging, very sus ceptible to fruit rot, (very) vigorous growth 'ioletta 1992 24.0 63 mg 2nd week of = Bpr 1249C, oblong August dark-blue, 14.5 % brix, horizontal hanging, (very) vigorous growth t/J 63 1995 6.8 84 mg mid- elliptic/egg-shaped, dark- September blue, 16.0 %brix, rather vigorous growth, (very) upright Rootstock: St. Julien A. Planting distance: 4.00 x 2.75 meters. In 1991, 1992 and 997, several cultivars did not crop mainly due to night frost in the flowering period, m = moderate; mg = moderate to good; g = good i June and July, it frequently rained and as a result hardly any cherry fruit could be arvested undamaged. The percentages of cracked and rotted fruit were high (Table
51 A.R. 1997 Fruit Research Statior
40). The production and average fruit weight were strongly affected by the often pooi fruit set and the abundance of rain afterwards. Fruit set was sometimes so poor, thai some cultivars could not be judged. In Table 40, the most important results of 3C cultivars are summarized in order of period of ripening.
In 1997, spring frosts occurred four times at Rillaar: 7 April (-0.8 °C), 8 April (-0.3 °C) 21 April (-2.0 °C) and 23 April (-1.0 °C). During the first spring frosts period, mos cultivars were at pre-bloom stage, some early flowering cultivars, such as Lapins, hac already some open flowers. At that time only a few flowers had been damaged. The second spring frosts period took place at full bloom. After these frosty nights, the percentage of damaged flowers on upwards of 20 cultivars was assessed. In general the damage was considerable (up to 80% damaged flowers), but the cultivars Hartland Lapins and Regina were relatively undamaged.
Cultivar trials with sweet cherry at Ahrweiler, Germany
M. Balmer and H. Kemp
Due to severe spring frosts during the flowering period in 1997, hardly any result wai achieved in the SLVA trial field at Ahrweiler, Germany. In 1997, some 100 cultivan were under trial at Ahrweiler.
Table 40. Data of sweet cherry cultivars at Rillaar, Belqium in 1997 Cultivar Harvest Fruit Produc- % rot and Remarks date weiqht M tivity 2) cracked 3) Vittoria seedl. 27 June 7.4 6 45 deep cracks Adriana 1 July 7.2 4 43 Hartland 1 July 8.3 3 71 deep cracks J.I. 11.343 1 July 9.6 6 36 cracks on the sean and around the style scar Na 12/21 1 July 10.9 5 73 Na 18/27 1 July 9.4 7 47 Newstar 1 July 9.2 - 94 Salmo 1 July 8.1 2 100 deep cracks all over Sasha/GM9 1 July 7.8 7.5 95 long deep cracks Starking H. Giant 1 July 7.5 7 40 V 69062 1 July 8.6 3 73 V 690618 1 July 8.5 4 92 Vit 2.14.91 1 July 6.4 3 16 Vit 4.9.91 1 July 6.0 2 •48 Vit 7.1.91 1 July 8.1 2 48 Botond 4 July 5.8 8 26 Sam/Edabriz 4 July 6.1 6.5 34 cracks on the seam Sam/GM61/1 4 July 7.6 8 56 Sel. .d. Ende 4 July 8.5 3.5 24 Nadino 7 July 9.0 - 95 firm fruit flesh
52 A.R. 1997 Fruit Research Station luby 7 July 9.1 1.5 73 Somerset 7 July 8.4 6 79 fixed fruits îtar 7 July 8.5 2.5 53 iummit/GM9 7 July 10.4 4 80 iylvia 7 July 9.8 3 53 'echlovan 7 July 11.4 5 75 4 'echlovan ) — 12.0 7 -5) rather soft, taste good 'ernon 7 July 8.4 - 66 'it 4.8.91 7 July 9.3 5 75 small cracks, firm, low,
incidence of fruit rot »unburn 10 July 8.4 5 82 4 iktavia ) — 12.1 3 67 6) often deep cracks 4 Sarina ) 11.4 5 59 6) shallow small cracks around style scar 3S-49-24 14 July 10.2 4 80 high incidence of fruit rot itn. Hedelfinger 14 July 9.0 7 — low incidence of fruit rot and cracks :olney/GM9 14 July 10.3 3 — soft fruits ordia/GM61/114 July 9.1 5 — ordia/W158 14 July 9.4 8 — few cracks (shallow, style scar) ozerska 14 July 9.0 5 apins 14 July 10.1 4 — high incidence of fruit rot after cracking on style scar weetheart/GM919 July 7.7 cracks on style scar, high incidence of fruit rot A sample of 20 fruits was weighed annually, ater which the average fruit weight was calculated in grams. Productivity scale from 1 to 9; 1 = very low, 6/7 = good and 8/9 = over-producti ve. Cracking susceptibility was evaluated in two ways: By observation of the percenta ge of splitted fruits on the tree, and/or by calculating a cracking index. With this method, 50 fruits are put in distilled water and after 2, 4, and 6 hours the numbers of splitted fruits are counted. In 1997, the amount of rotted and of splitted fruits was taken together, grown in glass house — = not observed cracking index; other percentages given in this column are percentages of splitted fruits observed on the tree
53 A.R. 1997 Fruit Research Statioi
Small Fruit
Cultivar testing with strawberry
A. J.P. van de Waart and J. Dijkstra
Evaluation of everbearing cultivars in the open (Wi9704)
At the present time, the culture of everbearing strawberries is of minor commercie importance in The Netherlands. In the main, cold-stored waiting-bed plants are used ti provide a late harvest. However, on heavier clay soils, everbearing cultivars are a gooi alternative for a harvest period from July onwards. Therefore, several new everbearini selections and cultivars were tested. In addition to being grown on clay soil in Th Netherlands, everbearing cultivars were also grown on heavier loes soils in the Belgia province of Limburg. That's why the cultivar trials are set up in co-ordination with th 'Demonstratiebedrijf voor Kleinfruit' at Tongeren, Belgium.
Tabel 41. Growth and flowering characteristics (average values for assessments on June, 15 July and 12 September 1997) ') Cultivars Plant- Growth Leaf Leaf Even Flower Numbei type vigour colour size ness habit flowers / truss Rapella 4.4 5.2 6.0 5.5 5.0 * 5.8 5.6 Evita 4.9 4.5 3.2 4.8 4.8 5.4 5.6 Bolero 4.1 5.2 5.0 5.0' 3.2 4.6 4.6 CPRO 9708 4.9 5.4 5.3 6.1 5.4 3.3 5.1 CPRO 9709 5.3 4.6 5.4 5.3 5.0' 4.9 5.2 CPRO 9710 5.5 * 4.3 5.0 " 5.0* 4.6 3.4 4.6 Everglade 5.0 * 4.5 " 5.1 3.8 5.2 6.7 6.1 Everest 3.4 6.4 6.6 6.8 6.0* 5.6 6.1 Relatively large differences between the values of the replicates and/or of observât on dates M Explanation of characteristics: Plant type 3 upright 7 = open Growth vigour 3 = weak 7 = strong Leaf colour 3 = light green 7 = dark green Leaf size 3 = small 7 = large Evenness 3 = uneven crop 7 = even crop Flower habit 3 = within the leaf canopy 7 = above the leaf canopy Number flowers/truss 3 = few 7 = many
The trial was comprised of 4 blocks of 8 everbearing cultivars and selections, each wi1 15 plants. The planting distance was 100 x 33 cm. All plants were established in Apr
54 A.R. 1997 Fruit Research Station fter 3 to 4 weeks of forcing under glass in pots, using plants that were cold stored rom December until March. The following cultivars were tested: Rapella, Evita (both as tandard cultivar), Bolero (Meiosis, UK), selections number 9708, 9709, and 9710 3PRO-DLO, Wageningen, The Netherlands), and Everglades and Everest (P. Vinson, IK). At Tongeren, Belgium Selva was the standard cultivar instead of Rapella. he plant characteristics were assessed three times during the season (Table 41). It ppeared that some characteristics changed during the season. For instance the plants f the selection CPRO 9710 grew rather open at the beginning, but later on became lore upright. The reverse was true for Everglade: at first the plants of this cultivar rew upright and later on more open. The Everglade plants grew vigorously at the eginning, but the growth vigour lessened during the season. The leaves of the CPRO 710 plants produced at the end of the season were smaller than those produced at ie beginning. The reverse was true for Bolero plants: leaves produced at the end of ie season were of a larger size than those produced at the beginning. In some plots ie crop of Rapella and CPRO 9709 became more even in the course of the season, but jr Everest the crop in some plots became more uneven in the course of the season. he growth of Everest plants was very strong and upright. In contrast, the plants of the PRO selections grew rather open, and the growth of the plants of the selections 9709 nd 9710 was not so vigorous. The crop of Bolero was rather uneven. The flower usses on the plants of the CPRO selections grew within the leaf canopy, whereas lose of Everglade extended above the leaf canopy. Everglade and Everest had the rgest flower trusses. he production characteristics are summarized in Table 42. The cultivars Everglade and verest, raised in the UK, were the most productive, followed by the cultivars Evita and apella. The production of the CPRO selections was disappointing. In addition, these ïlections were rather susceptible to powdery mildew. The selection CPRO 9709 roduced the lowest percentage of rotten fruit, followed by the cultivars Evita and verest. able 42. Production characteristics in kg/m2 (harvest period 17 June to 26 Septem- ber 1997) ultivar/ Qual.l Qual.l Qual.ll Rot % I % Av.fr. Mean election (l + sm) small (l+ ll ) rot wt.(g) harvest I date apella 1.85 0.35 0.36 0.23 83.7 9.6 11.6 9 Aug. i/ita 2.05 0.30 0.33 0.17 86.4 6.6 13.5 3 Aug. Dlero 1.46 0.23 0.21 0.18 87.4 9.6 12.8 4 Aug. PRO 9708 1.14 0.09 0.22 0.23 83.9 14.3 12.7 15 Aug. PRO 9709 1.67 0.29 0.20 0.08 89.3 4.3 12.5 4 Aug. PRO 9710 0.83 0.19 0.20 0.09 80.5 8.4 10.0 16 Aug. /erglade 2.30 0.45 0.34 0.25 87.0 8.5 15.6 24 July /erest 2.25 0.21 0.25 0.17 89.9 6.2 14.9 1 Aug.
55 A.R. 1997 Fruit Research Statio
Due to the very warm weather at the end of July and in August the flower trus formation of all cultivars/selections ceased almost completely in that period, and th formation begun again in September. However, this recovery came too late to produc an acceptable yield in September/October. Therefore, the mean harvest date in 199 was relatively early. Picking started first with Everglade, resulting in the earliest mea harvest date. Only the CPRO selections 9708 and 9710 had a late mean harvest dat< due to a delay in the onset of growth. However, this delay and the cessation in flow« truss formation resulted in a low fruit production. A number of fruit quality characteristics have been assessed twice during the pickin period (Table 43). The selection CPRO 9710 and the cultivars Everglade and Evere; gave a fairly uniform fruit crop. The fruit size of the cultivar Bolero was disappointin and the firmness was moderate. In addition Bolero had orange coloured fruits, wherec Everglade and Everest had dark red fruits. Differences in taste were small. On Everglade fruit had a less satisfactory taste. Remarkably, the fruits of Evita and CPR 9710 tasted much better in September than at the beginning of July. The standard cultivars Rapella and Evita were quite satisfactory. This was not the cas with the CPRO selections due to production being too low and their susceptibility 1 powdery mildew. Bolero also was not satisfactory: production was moderate and tr quality of the fruits was below standard. Everglade and Everest were relatively high production and the quality of their fruit varied from acceptable to rather good.
Tabel 43. Assessment values for fruit characteristics (1 July and 2 September 1997] Cultivars/ Crop Size Colour Fruit Firm- Taste Juci- Overa Selections unifor- unifor- ness ness impre mity rnity sion Rapella 4.5 6 6 6* 6 5.3 6 6 Evita 3 5.5 5 6 5.5 5* 5* 5.3 Bolero 4 4 3 5 4 6 4.7 5.5 CPRO 9708 6.5 6 7 6 5.5 5.3 4.3 4.5 CPRO 9709 4.5 5 6 5 6.5 5 4.3 4.5 CPRO 9710 6 6 5 7 7 5* 6.7 4.5 Everglade 5 6 8 5 6 4.3 7 5.5 Everest 6 6* 9 6 6 6 7 5.3 * Relatively large differences between the values of the replicates and/or of observa on dates 1) Explanation of characterist cs: Crop uniformity 3 = not uniform 7 = uniform Size 3 = small 7 = large Colour 3 = light orange 7 = dark red Fruit uniformity 3 = deformed 7 = regular Firmness 3 = bad 7 = good Taste 3 = bad 7 = good Juiciness 3 = few 7 = much Overall impression 3 = bad 7 = good
56 A.R. 1997 Fruit Research Station
Cultivar descriptions ( based on the results of the trial in 1997)
Rapella Growth: Rather vigorous; moderately open plant type; somewhat dark green and rather large to large leaves with rather long leaf stalks. Blossom: Firm flower truss stalks extending just above the leaf canopy; rather too many flowers per truss. Productivity: Good production. Fruit exterior: Rather large to large fruits, not so uniform in size, ellipse to egg shaped; bright red colour. Fruit quality: Rather solid and fruits not easily damaged; fruit flesh colour white to light orange-red; taste rather good to good; fruits rather sweet and juicy. Diseases and njuries: No particular susceptibility diagnosed
Evita Growth: Rather upright; rather moderately vigorous; leaves moderately sized with a very light green colour. Blossom: Flowers positioned at the same height as the leaves, or just above the leaf canopy; rather too many flowers per truss. Productivity: Good to very good production. Fruit exterior: Rather large fruits, but not so uniform in size; regular cone shaped. Fruit quality: Rather solid and moderately easily damaged fruits; fruit of a fresh red colour; fruits at first rather moderately flavoured and not so juicy, but later taste and juiciness improved; fruits sufficiently sweet and acid and moderately aromatic; the calix could not easily be removed. Diseases and njuries: Cultivar seems not to be very susceptible to fruit rot and powdery mildew.
Bolero Growth: Rather upright growing plant type; moderately vigorous; at first leaves moderately sized, later in the season somewhat larger. 3lossom: Flowers positioned at the same height as the leaves, or just below the leaf canopy; a moderate number of flowers per truss. 3roductjvity: Moderate production. zruit exterior: Moderately uniform in size; rather small and somewhat ellipse in shape. zruit quality: moderately solid, easily damaged fruits; fruit flesh white coloured; taste rather good to good; fruits rather juicy and sweet, but not much acid and not aromatic. Diseases and njuries: Crop height was rather uneven, the cause of this is unknown.
ÎPRO 9708 growth: A moderately open plant type; moderately vigorous; rather large, normal
57 A.R. 1997 Fruit Research Statior
green coloured leaves. Blossom: Flower stalks short, flowers positioned within the leaf canopy; a mode rate number of flowers per truss. Productivity: Very moderate production. Fruit exterior: Rather large, cone-shaped fruits of rather uniform size. Fruit quality: Moderately solid and fruit moderately susceptible to damage fruits; frui flesh of a red colour; fruits have a moderate to moderately good taste are moderately juicy and rather moderately aromatic. Diseases and injuries: Very susceptible to powdery mildew; seems susceptible to fruit rot.
CPRO 9709 Growth: A moderately open plant type; moderately vigorous; moderately size« and normal green coloured leaves. Blossom: Flower trusses positioned near leaf canopy height; a moderate numbe of flowers per truss. Productivity: Moderate production. Fruit exterior: Rather large, cone-shaped fruits of rather uniform size; fruits red t< bright red colour. Fruit quality: Solid fruits; at first not easy damaged, but later in the season somewha more susceptible to damage; fruit flesh white to light orange coloured fruits have a moderate taste, are not so juicy and not very aromatic. Diseases and injuries: Very susceptible to powdery mildew; appears not to be very susceptible to fruit rot.
CPRO 9710 Growth: Plant vigour rather moderate; at first leaves light green coloured and of ; large size, but later in the season more dark green coloured and smalle sized. Blossom: Flower stalks short, the flowers situated mostly within the leaf canopy a moderate number of flowers per truss. Productivity: Poor production (may have been caused by the very hot weather). Fruit exterior: Moderate to rather large fruits; somewhat kidney-shaped; fruits re« coloured. Fruit quality: Solid fruits, not easy damaged; fruit flesh of intensive red colour; tasti somewhat variable, but predominantly good; juicy, rather sweet an< quite aromatic. Diseases and injuries: Very susceptible to powdery mildew.
Everglade Growth: At first rather upright, later on a more open plant type; the early yielding went hand in hand with a decreasing plant vigour at that time of thi season; leaves rather small and moderately green. Blossom: Large flower stalks extending above the leaf canopy; many flowers pe
58 A.R. 1997 Fruit Research Station russ. 'roductivity: Very good production. :ruit exterior: Large, somewhat kidney-to-cone-shaped fruits; rather uniform in size; fruits of red to dark red colour. :ruit quality: Solid fruits, not easily damaged; fruit flesh red coloured, juicy; taste very moderate to moderate; a decreasing sweetness of the fruit during the yield period; the calix could not easily be removed. Diseases and njuries: No particular susceptibility diagnosed.
Iverest rowth: Very vigorous, upright growth; large, dark green leaves. Slossom: Position of flowers near or just above the leaf canopy; rather many to many flowers per truss. 'roductivity: Very good production. :ruit exterior: At first large, later on smaller, dark red coloured fruits; fruits uniform in size, cone-shaped to broad wedge-shaped. :ruit quality: Solid fruits; at first not easily damaged, but later on somewhat more easily damaged; fruit flesh red coloured; taste good, rather sweet, increasingly aromatic and not much acidity; the calyx could not easily be removed. Diseases and ijuries: No particular susceptibility diagnosed.
Cultivar testing with strawberry
\.J.P. van de Waart and L. Bolijn
Comparison of Elsanta from different origins
)ften strawberry growers suggest that nowadays the fruit quality of Elsanta is no )nger as good as it was immediately following the introduction of this cultivar. They alk about degeneration of the cultivar. Therefore Elsanta from several origins was Bsted for growth and production characteristics. The plants from these origins (clones) i/ere propagated and cultured differently for a period of years. In February 1996 (96F), larch 1997 (97M) and August 1997 (97A) trials were carried out at the Experimental tation at Breda, in which Elsanta from 10 origins was tested (see Table 44 and 45). trial 97M, plants of origin France 1 blossomed two days earlier than those of letherlands 1 and five days earlier than those of France 3 and France 4. In the other wo trials differences in the start of blossoming were small. In each trial plants from rigin Italy were not so vigorous. In trial 97A, these plants had also shorter flower talks and smaller leaves than plants from other origins. In trial 96F and 97M plants om origin Switzerland had thicker flower and leaf stalks than plants from other rigins. Plants from origin Italy produced somewhat less stolons than plants from other
59 A.R. 1997 Fruit Research Statioi origins: in total per plant almost three stolons less were removed than from plants fron origin Netherlands 1. Production of stolons hardly differed between plants from tru other origins.
Table 44. Total production (kg) of Elsanta from different origins per trial (code sei text) and production summarized over the 3 trials Origin 96F 97M 97A Total productior Netherlands 1 5.61 abc 86.9 a 88.8 d 89.2 Netherlands 2 5.48 a 88.6 a 89.5 d 89.9 Italy 5.50 ab 84.6 a 85.0 bc 86.7 Sweden 5.95 cd 86.3 a 83.8 b 87.1 Switzerland 6.09 d 86.3 a 80.1 a 85.4 Germany 5.65 abc 87.1 a 88.0 cd 88.5 France 3 6.07 d 85.8 a 83.0 ab 87.4 France 4 5.86 bed 86-.9 a 87.3 cd 88.6 France 1 5.94 cd 87.2 a 85.1 bc 88.6 France 2 6.18 cd 88.6 a 87.8 cd 89.7
LSD 0.05 0.35 0.30 0.38 F-test * * * * * * * •
In 1996, the highest fruit production was achieved. Plants from origin Switzerland am France 3 produced well in all three trials, whereas plants from the origin Italy had thi lowest fruit production.
Table 45. Fruit quality I (% of quality I and II) of Elsanta from different origins pe trial (code see text) and fruit quality I (% of quality I and II) averaged ove the 3 trials Origin 96F 97M 97A Average Qual.1 Netherlands 1 92.1 bed 86.9 a 88.8 d 89.2 Netherlands 2 91.6 bed 88.6 a 89.5 d 89.9 Italy 90.4 ab 84.6 a 85.0 bc 86.7 Sweden 91.1 bc 86.3 a 83.8 b 87.1 Switzerland 89.9 a 86.3 a 80.1 a 85.4 Germany 90.4 ab 87.1 a 88.0 cd 88.5 France 3 93.3 d 85.8 a 83.0 ab 87.4 France 4 91.7 bed 86.9 a 87.3 cd 88.6 France 1 93.0 cd 87.2 a 85.1 bc 88.6 France 2 92.7 cd 88.6 a 87.8 cd 89.7
LSD 0.05 2.2 nb 3.5 F-test * ns * * *
60 A.R. 1997 Fruit Research Station n 1996, the highest percentage of quality 1 fruits was harvested from plants in each )f the origins. Plants from the origins Netherlands 1 and 2, and France 2 produced on iverage the highest percentage quality 1 fruits; those from origin Switzerland produced he lowest quality 1 fruits. Many sepals were present on the fruits harvested from liants from origin Switzerland (all trials), France 4 (trial 96F and 97M) and France 3 trial 97M). In the trial 96F, fruits from plants from origin Switzerland were of a omewhat darker colour, were not so uniform in size and had a less satisfactory taste han those from other origins. n spring 1997, no genetic differences could be established by the CPRO-DLO Institute it Wageningen, The Netherlands, by means of iso-enzyme tests between plants from lifferent origins. In the autumn of 1997, tests were run for DNA similarity. In five out
>f ten samples distinct DNA band patterns were established, which represent different )NA fragments. In total 33 bands could be used for mutual comparison. Plants from me origin revealed the same DNA band pattern as plants from origin Netherlands 1. 3lants from two other origins had the same band pattern as the plants from origin Jetherlands 1, plus four extra DNA bands. Plants from one origin had a distinctly ifferent band pattern from plants from the four other origins. The results suggest that hanges have occurred in the cultivar Elsanta. Extended research has to be carried out o clear the status of the different plant origins.
Cultivar testing of bush and cane fruit crops
M.A.G.M. Jansen
irst evaluation of blueberry cultivars
spring 1991, 2-year-old bushes of the cultivars Cape Fear, Blueridge, O'Neal, îharpblue, Avonblue, Denise Blue, Blue Rose, Caroline Blue and Brigitta Blue were ilanted for a first evaluation of production and fruit quality. Brigitta Blue, Denise Blue, aroline Blue and Cape Fear appeared to have the highest production (Table 46).
able 46. Blueberry, production (kg/bush) and average fruit weight (Av.fr.wt) Cultivar Origin Production Production Av.fr.wt. (g) 1997 92'97 1997 ^ape Fear U.S.A 0.97 5.96 1.7 llueridge U.S.A. 0.15 2.89 1.8 0 Neal U.S.A. 0.44 3.11 1.9 »harpblue U.S.A. 0.05 1.30 2.0 Jenise Blue Australia 0.70 6.36 2.8 Hue Rose Australia 0.95 4.95 1.9 laroline Blue Australia 0.55 5.57 1.6 rigitta Blue Australia 1.16 7.53 2.0
61 A.R. 1997 Fruit Research Statioi
Avonblue and Sharpblue gave the lowest yield. Sharpblue, O'Neal and Cape Fear an early producing cultivars (Table 47). Blueridge, Avonblue and Blue Rose are early-mid season producing cultivars. Brigitta Blue is a mid-season producing cultivar and Denisi Blue and Caroline Blue are mid-late producing cultivars. The growth vigour (vitality) of the cultivars Blueridge and Sharpblue is rather low. Ii addition, Sharpblue is susceptible to Botrytris cinerea. The cultivars Brigitta Blue Caroline Blue, Cape Fear, Blue Rose and O'Neal are the most promising ones and will bi tested further. Bushes of the cultivar Avonblue were scrubbed in 1997.
Table 47. Blueberry, harvest data in 1997 and pickinq period First pick Mean harvest Last pick Pickingperio « 5% 50% 95% (weeks) Cape Fear 3 July 6 July 14 July 1 - 3 Blueridge 16 July 24 July 13 Aug 2.5-4 '0 Neal 3 July 5 July 14 July 1.5- 3 Sharpblue 3 July 5 July 6 July 2 - 5 Denise Blue 5 July 29 July 16 Aug 3.5- 6 Blue Rose 13 July 30 July 11 Aug 3 -4 Caroline Blue 23 July 5 Aug 17 Aug 1.5-6 Briqitta Blue 9 Julv 25 Julv 5 Aug 3-4
Development of methods for an early and late harvest of bush an< cane fruits
W.A.G.M. Jansen
Delayed harvest of blueberry due to use of rain cover
Accumulation of supply in the middle of the harvest season leads to low prices, evei with blueberries. Therefore, one is searching for methods to spread the harvest period A first possibility is a good choice of cultivars. In addition to, both the delay of harves by growing the bushes under a plastic rain cover and cold storage of the berries afte harvest can contribute to a further spread of the blueberry season. In a pilot trial at the Experimental Station for Fruit Growing at Horst the effect of a rail cover on production and harvest period was examined for the cultivars Bluecrop, Covllli and Elliott. Bluecrop and Coville were both planted as 2-year-old bushes in a trial witl planting systems in 1986; 2-year-old bushes of Elliott were added in spring 1994. The production in 1997 and the total production over the years 1994-'97 is summari zed in Table 48. For each cultivar the results can be summarized as follows.
Bluecrop - in 1994 and 1995 the bushes under rain covers gave a higher productio than those without cover. However, in 1996 production under rain cover was somew hat lower than without cover. On average over 3 years, differences in production wer very small. In 1994 and 1995 the average fruit weight of the bushes under rain cove
62 A.R. 1997 Fruit Research Station
/vas higher than that of the uncovered bushes. In 1996 there was no difference in fruit weight. By growing bushes of Bluecrop under a plastic cover it was possible to extend he harvest period by 1 to 3 weeks. The mean harvest date of the bushes under cover anged from 21 July to 4 August and that of the uncovered bushes from 15 to 16 July.
"oville - in 1994, 1995 and 1996 bushes under rain cover were more productive than jncovered bushes. Also, the average fruit weight of the covered bushes was higher in ill years. However, there was little effect from the plastic rain cover on the extension )f the harvest season: 0 to 10 days. The mean harvest date of the bushes under rain over ranged from 6 to 9 August and that of the uncovered bushes was on 29 July.
Iliot - in 1995 the production from covered and uncovered bushes was equal and in 1996 bushes under rain cover were somewhat more productive than the uncovered >nes. However, in 1996 the average fruit weight of the bushes under rain cover was omewhat lower than that of the uncovered bushes. With Elliott it was possible to xtend the harvest period under a plastic rain cover by 1 to 2 weeks.
Table 48. Production in tons per ha in 1997 (average fruit weight in grams) and over the years 1994-1997 'lanting Bluecrop Coville Elliott ivstem 1997 '94'97 1997 '94'97 1997 '95'97 Jushes with rain cover 3ush 3200 5.0 (2.5) 37.3 11.3 (2.1) 41.8 Hedge 3200 5.6 (2.7) 46.5 10.0 (1.9) 40.8 iush 6400 6.9 (2.6) 62.7 18.7 (1.8) 66.2 Hedge 6400 8.4 (2.6) 73.1 18.6 (1.7) 73.1 iush 5000 - ... 6.0(1.8) 15.3
Jncovered bushes iush 3200 11.0 (2.7) 61.0 3.7 (2.0) 24.2 ledge 3200 6.7 (2.5) 43.1 6.9 (1.9) 34.0 lush 6400 13.1 (2.4) 67.0 8.4 (1.9) 40.3 ledge 6400 12.2 (2.3) 69.9 9.8 (1.9) 41.8 lush 5000 _ _ _ _ 4.5(1.7) 10.9
63 A.Ft. 1997 Fruit Research Station
Economics and Farm Management Analysis
Root pruning
J.G. Drabbels (trainee, HAS, Den Bosch) and M.J.Groot
The results of various root pruning trials with apple and pear were economicallv evaluated. Red Boskoop, Delcorf and Elstar were the apple cultivars involved, and th€ pear cultivars were Conference and Doyenne du Cornice. Often root pruning led to e loss of production. Nonetheless root pruning came forward as an "emergency treat ment" with apple, because the growth check caused by root pruning can lead to e longer orchard life-span and a reduction in labour for pruning. Root pruning, carried oui at the right time, may give an increase in production with pear and may therefore leac to positive economic results. More detailed information is published in Fruitteell 87(1997)42:12-13.
Integrated fruit growing
M.J. Groot
In 1997 a comparison of three ways of crop protection with various apple cultivars a two locations (Numansdorp and Zeewolde), came to an end. The economic evaluatior of this trial has been published in Fruitteelt 87(1997)36:14-15. The complete descripti on of the trial will be published in a separate FPO-publication. The trial started in 1990 and consisted of three different ways of crop protection current, integrated and minimum The annuity net present value (ANPV) was highest for the current system, ƒ6,17E (averaged for the apple cultivars involved). The ANPV for the integrated systen amounted to ƒ5,583 and for the minimum system to ƒ4,002. This calculation wa; based on the assumption that the life-span is equal for the three systems. This migh not be the case with the minimum system, where trees were lost due to fruit-tret canker during the 7 years of this trial. Therefore, it is doubtful whether this planting wil be able to have a life-span of 12 years like the other two systems. A shorter life-spar leads to a lower ANPV. Besides the ANPV, a calculation was made of the extra kg price needed for th< integrated and the minimum system to reach the same economic results as the curren system. During the 7 years of the trial, apples from the integrated system needed ar additional 2.9 cents/kilo and the apples from the minimum system an additionall0.( cents/kilo to reach an equal result. This extra price is an average for the variou: cultivars. The extra price differed greatly between the cultivars.
64 A.R. 1997 Fruit Research Station
'lant Nutrition and Fruit Quality
•torage and quality
)ptimum storage conditions and ability to use storage techniques n pome fruit
P.MM. Roelof s ew varieties
the season 1996-'97 the apple cultivars Topaz, Goldrush, Braeburn (and mutants raeburn Superstar and Breastain) and Ahrista and on the pear cultivars Delbuena and elmoip. All fruits came from the research station in Wilhelminadorp. The trees were eated normally, with the exception of Topaz (scab resistant) which was not treated nth any fungicide. Before the estimated optimum harvest date, samples were taken ver a period of 4 weeks from each cultivar to follow the maturity development. the estimated optimum harvest date a number of trees were picked completely, fter randomising, the fruits were divided and put into different storage conditions egular storage and ULO storage at different carbon dioxide levels). Inner and outer uits were picked separately from Goldrush and Delmoip. l addition Dutch grown fruits some German fruits were also examined. Dr. Streiff xchanged some Topaz fruits from Wilhelminadorp to Santana. opaz stored well until mid-March. Loss of firmness was relatively high during ULO- nd regular storage. High levels of carbon dioxide did not appear to be suitable. oldrush remained green and firm during storage. After a long period of storage the aste was good, a little better than Golden Delicious. It is not clear if Goldrush will lature in the Dutch climate. raeburn showed several internal disorders. It would appear that Dutch grown fruits annot be stored. hrista ripened rapidly during storage. Firmness losses were high during regular and LO storage. Internal disorders developed rapidly during shelf life. elbuena did not store well under all test conditions. Extremely low carbon dioxide vels might be more successful. elmoip appeared to store well. Low oxygen concentrations reduced the loss of ackground colour but did not affect firmness.
65 A.R. 1997 Fruit Research Statio
Storage ability of cherries
F.P. M. M. Roelofs
In 1997 the effect of storage conditions and lenght of storage was examined o Lapins and Kordia. Fruits from the research station were assessed after 31 and 54 day of storage. Lenght of storage and carbon dioxide levels affected most quality parameters. Th colour of the stems and the fruits altered during storage. The acid level and the tast reduced during storage, firmness increased. For stem, fruit colour and taste th optimum carbon dioxide levels were 10-20%. The number of rotten fruits reduced t higher carbon dioxide levels. High sugar levels were found after storage at low oxyger
Reduction of internal disorders during storage of Conference pear.
F.P.M.M. Roelofs and A. de Jager
In co-operation with ATO-DLO, research on brown heart (cavities and browning of th fruit flesh) was carried out, not only to find the cause but also to establish practice guidelines by which to predict and avoid the risk.
Over a period of five weeks (starting two weeks before the estimated optimum harve; date) fruits were picked at seven orchards in the South-West part of the country. Som orchard treatments were carried out. In order to create variation in mineral compositior extra K, N and Ca was applied. At harvest maturity and quality tests were done. Fruits from each pre-harvest treatmer were split up at random into the necessary number of boxes for post-harvej treatments. The pears were stored in containers of _+ 1 m3. Gas conditions wer automatically measured and controlled every 2 hours. After storage (until April 199^ fruits with external disorders were removed. Quality measurements (including interni disorders) on the other fruits were carried out after a warming up period of 1 day an after 3 days of shelf life at 20 °C.
The length of the cooling period before CA-storage had significant effect o susceptibility to brown heart. The susceptibility reduced sharply after a cooling perip of 2 days compared to no cooling before CA. After a cooling period of 10 days th fruits were as susceptible as when there had been no period. Fruits were much les susceptible when the cooling period was increased to 21 or 50 days. Compared to rapid reduction of oxygen after 21 days, less brown heart was found after a slo\ reduction of oxygen. This pattern was found in fruits from all harvest dates but th differences were greatest in fruits from the latest harvest date. The different scenario had (almost) no effect on the firmness and sugar level after storage. Fruits were les green and more yellow (L*a*b system) after a long cooling period before CA. Thes differences were also found after 3 days shelf life. Following storage the level vitamin C was higher after a long cooling period before CA. Only after a cooling perio
66 A.R. 1997 Fruit Research Station
)f 50 days the vitamin C content became lower.
:ruits from some orchards appeared to be much more susceptible than fruits from other irchards at the same harvest time. Differences in vitamin C (after storage) did not :orrelate well with the susceptibility to brown heart.
Jrown heart did not develop gradually during storage. Disorders were found in mature tears (last pick) after 1 month of storage. After 15 November the total amount of pears vith disorders did not increase further. Later (after mid-January) a second sharp icrease in disorders was found.
:rop load affects the fruit size. Thinning produced larger pears which were less ensitive to brown heart. Natural differences in bearing (by flowering, drop etc.) had no ffect on the susceptibility. Firmness was a little higher in objects with low bearing. "he sugar level was only affected by extreme thinning. tuits from the top of the tree were larger, less firm and most sensitive to brown heart. nner fruits were smaller, firmer and contained less sugar. Susceptibility to brown heart eemed to be correlated with vertical position and quality with horizontal position on he tree. additional nutrition had no effect after one season. A most frequent supply might be nore effective. kstres s test at 20 °C and combinations of 1 and 21%oxyge n with 3 and 10% carbon ioxide induced disorders (browning) within 2 weeks. In general low oxygen objects iduced less disorders than high oxygen objects. The effect of carbon dioxide was regular. The correlation between the stress test results and brown heart after storage »/aspoo r (cc <0.3). )rchard, mineral composition and quality parameters at harvest and after storage were orrelated with susceptibility to brown heart. Models based on firmness, sugar level, tarch, acid and internal volume were developed to predict cavities (56%) and rowning (45%). malyses of data showed that within a given plot, the largest fruits were the most ensitive to brown heart. lowever, the effect of fruit size is too small to sort unhealty pears from healthy pears..
»torage of Delblush/Tentation
.P.M.M. Roelofs and A. de Jager
ï 1996 the research on optimum harvest date and optimum storage conditions was egun. Starting on 16 September the development of the fruits was followed. Fruits jr storage were picked on 18 and 29 October. Fruits from the inner part of the trees rere kept separate from the rest at the last harvest date. Fruits of each harvest date rere stored at 3 ULO conditions (1°C, 1.2% oxygen and 1, 3 or 5% carbon dioxide) nd in regular storage until May. Jonagold and Golden Delicious were put in the same tores to compare quality losses. Quality was measured after a warming up period of 1
67 A.R. 1997 Fruit Research Statior day, after 1 week of shelf life at 10°C and after another week of shelf life at 20 °C. At harvest Delblush fruits were firm. Losses during ULO storage and shelf life wen small (less than Jonagold or Golden Delicious). Late harvested fruits had greater loss o firmness . Even after 2 weeks of shelf life firmness was higher than 4.5 kg. Backgrount colour, sugar and acid were preserved more effectively in ULO compared with régula storage. Between the different ULO conditions only small differences in fruit quality were observed. The fruits were susceptible to scald (especially during shelf life). Late harvested fruit! from the outer part of the tree were most susceptible. ULO stored fruits were les! susceptible than fruits from regular storage. In general, in taste tests, Delblush was judged' better than Golden Delicious anc Jonagold.
Storage of Santana
F.P.M.M. Roelof s
In 1996-'97 research was carried out on optimum harvest date and optimum storag« conditions. Fruits from 5 harvest dates (between 2 and 30 September) were assessec after regular storage and ULO storage. Fruits harvested at the expected optimun harvest date were stored in regular storage and 3 ULO conditions (1°C, 1.2% oxyget and 1, 3 or 5% carbon dioxide). During ULO storage almost no firmness was lost. There was also very little loss o firmness during shelf life. Differences in firmness between fruits from different harves dates remained during storage and shelf life. Firmness and acid losses were greate during regular storage. During ULO storage the background colour was maintained During shelf life fruits became yellow and sometimes fatty. Internal browning developed during storage and (especially) during shelf life. Th< highest losses were observed after a long period in regular storage. Less problems wer« found in early harvested fruits after ULO storage. Late harvested fruits tasted as good as Elstar, early harvested fruits had less taste Storage conditions had very small effect on taste.
Storage of blueberries
F.P.M.M. Roelof s
Mature and immature fruits of Bluecrop and Coville were put in store at 1 °C for 3, E and 7 weeks. Storage conditions were combinations of 21, 10 and 5% oxygen and 0 5, 10 and 15% carbon dioxide. Bluecrop had less rotten fruits than Coville. Carbon dioxide impressed rotting mos effectively. Immature fruits were less susceptible to rotting. The oxygen level hac almost no effect on rotting. Bluecrop lost its firmness more quickly than Coville. Mos soft fruits were found after storage at 15% carbon dioxide. The high carbon dioxidi
68 A.R. 1997 Fruit Research Station
3vel also affected taste; oxygen had no effect. The acid concentration was lowest in ruits stored at high carbon dioxide levels. kdvised storage condition (after 1 year of research): 1 °C, 10% oxygen and 10% arbon dioxide.
Differences between Cox mutants
'.P.M.M. Roelofs and H. de Putter. rom two weeks before until two weeks after the estimated optimum harvest date (3 o 30 September), fruits were picked each week from 2 trees (with normal bearing) of 0 Cox's O.P. mutants (T 12, La Vera, Roelse, Van der Rijdt, Flikweert, EMLA, Queen ox 4, Queen cox 13, Queen cox 91 and Queen cox Heines). The fruit diameter and lush area of all fruits (AWETA) was measured; quality and maturity was measured on sample of 25 fruits. The other fruits were stored at 4 °C, 1.2% oxygen and < 0.5% arbon dioxide until 17 February. After storage, weight loss was measured and fruits i/ith external disorders were removed. Quality measurements were recorded after a /arming up period of 1 day, after 1 week of shelf life at 10 °C and after another week t 20 °C. he differences between the mutants were not large. Roelse, Queen Cox 13 and Queen lox 91 had the highest scores. The 2 Queen cox mutants were a little firmer than oelse. or more definite conclusions more replications are necessary. toil Science and Plant Nutrition nprovement of the advisory system for the fertilization of trawberries and other small fruitcrops grown in the open
1.P. van der Maas and M.C.J, op 't Hof
everal fertilization strategies were tested in 1997 for the strawberry (planted in June) n their efficiency of the nitrogen use: fertilization according to NBS (additional trogen fertilization bases on soil nitrogen amounts) and the use of GFT-compost or ow release fertilizers (Agroblen). In 1996 comparable strategies were studied and also ie use of chicken manure pellets.
oduction
ie average production over two years of the treatments with KAS/NBS (treatment 3 id 4) and Agroblen Special (treatment 5) was significant higher (p<0.05) than eatment one (see 49). The effect of organic manure (treatment 2) incomparison with
69 A.R. 1997 Fruit Research Statioi treatment one was nearly significant. Differences in production resulted fron differerences in fruit load.
Table 49. Results of 1996 en 1997 Year Treatment* Result** Organic Nitrogen Yield Firmness Nitrogen in Leaf Plant matter kq/m2 fruit leaf colour volume 1996 1. - - 2.65 0.265 68 3.00 3.0 13.1 2. VRM/29 - 2.82 0.230 73 3.29 3.5 13.9 3. - KAS/NBS 3.07 0.219 84 3.45 4.0 15.7 4. VRM/29 KAS/NBS 3.02 0.232 84 3.38 5.5 15.5 5. VRM/29 Agrob.Sp. 3.06 0.236 84 3.37 5.3 15.4
1997 1. - _ 2.04 0.132 87 2.67 5.3 10.2 2. GFT/18 - 2.13 0.133 86 2.66 5.4 9.5 3 - KAS/NBS 2.27 0.127 105 2.83 6.3 11.1 4. GFT/18 KAS/NBS 2.13 0.129 101 2.75 6.4 10.5 5. GFT/5 Aqrob. Sp 2.11 0.132 110 2.78 6.1 10.8 * In 1996 29 ton cow manure(VRM)/ha, calcium ammonium nitrate (KAS according to NBS (for amounts see table 50) and Agroblen Speciaal (1 g/plant); in 1997 18 or 5 ton GFT-compost/ha. ** Yield: total of class 1 and 2; Firmness in kg; Nitrogen in the fruit in mg N/100 fresh weight and in leaf g/100 g dry weight; leaf colour: visual assesment; plar volume just before harvest in L/plant.
Nitrogen uptake and growth
Corresponding with the higher fruit load also increased plant volumes for th treatments 3 till 5 were found (see table 49). Through more growht more flower bud developed. The increase in growht was probably induced by an increased nitrogen so nitrogen content and nitrogen uptake (higher leaf contents for the bigger plants). Als the leaf colour was darker green for these plants although the correlation between lei colour and nitrogen content was not strong: also mangenese and magnesium uptak was inportant for leaf colour.
Soil nitrogen
Increased soil mineral nitrogen amounts for the KAS/NBS-treatments are shown figures 1 and 2. The soil nitrogen measurements for the slow release fertilizi (treatment 5) were only carried out in 1997. The amounts were lower than for tr KAS/NBS treatments although the nitrogen uptake was simular. This can be explaine by the local availability of nitrogen, the slow release of nitrogen and the fact that tr soil close to the Agroblen pellets was not sampled to avoid sampling of the pelle themselves. The simular nitrogen uptake can be explained by local high nitroge contents and/or the direct uptake of released nitrogen through which the soil nitroge amount is not increased. The last proces was also found in 1996 with cow manure:«
70 A.R. 1997 Fruit Research Station creased nitrogen uptake in comparison with non treated plants (see table 49) though the soil nitrogen levels were not increased (see figure 1). The GFT-compost- eatment in 1997 did not show this, which could probably be explained by the lower lease of nitrogen or the unfavourable growing conditions in 1997. ptimal soil nitrogen amounts ccording to NBS the optimal nitrogen amounts in the soil for a strawberry crop anted in june are 65, 70 and 65 kg N/ha in the first 30 cm of the soil respectivily at anting and 5 and 8 weeks after planting. Figure 1 shows that the use of 3 ton nicken manure pellets resulted in 80 to 100 kg N/ha in the first 4 weeks. This higher trogen level did not result in an improved production in comparison with the 30 kg /ha of the NBS-treatments in this period (later in the season the amounts were Dmparable). From this can be concluded that the nitrogen requirements according to BS are "on the safe side". able 50. The nitrogen balances for 1996 and 1997 ear Treatment* Nitroge balance (kg N/ha) Organic Nitrogen Input Output Storage matter Organic** Fertilizer Total 1996 1. - 0 0 0 18 - 18 2.VRM/29 235 0 235 21 + 214 3. - KAS/NBS 0 60 60 27 + 33 4. VRM/29 KAS/NBS 235 68 303 26 + 277 5. VRM/29 Agrob. Sp. 235 73 308 27 + 281 6. Chicken M. KAS/NBS 75 43 118 28 + 90
397 1. 0 0 0 26 _ 26 2. GFT/18 184 0 184 19 + 165 3. KAS/NBS 0 90 90 25 + 65 4. GFT/18 KAS/NBS 184 71 255 23 + 232 5. GFT/5 Agrob. Sp. 51 85 136 26 + 110 Chicken Manure pellets: 1500 kg/ha, for other information see table 49 straw exluded
trogen balance
ie largests posts in the nitrogen balance are the applications of organic manure (see ble 50). Fertilization according to NBS or the use of Agroblen does not result in an fferent increase of the nitrogen storage. The 29 ton cow manure and the 18 ton GFT- impost are maximum allowed amounts (for GFT 18 ton per two years or 9 ton per iar). With the application of 5 ton GFT-compost the maintainance of the organic atter content of the soil was achieved. With cow manure 7 ton/ha was needed suiting in a comparable nitrogen input for both organic resources (51 and 57 kg/ha), l relatively low increase in storage of 110 kg N/ha with 5 ton GFT-compost in 1997 as achieved without loss of production. With 1500 kg chicken manure pellets
71 A.R. 1997 Fruit Research Statio
nn
100
_ 80 (0 sz 2 ~ 60 V Ol o Z 40
20
i i i i i i i i i t i i i 4-6 18-6 2-7 16-7 30-7 27-8 X-As
+. Treatment 1 _».Treatmen t 3+4 ^ Treatment 2 e Treatment 6 I
Figure 1. Dynamics of soil Nitrogen amount in the 0-30 cm layer of the soil i 1996 (for further explanation see text)
on
100 TO 80 - c 0) 60 o yS\ z 15 40 c
20
n i > i i . i ^^S^A 3-6 16-6 30-6 14-7 28-7 11-8 24-8
g. Treatment 1 a Treatment 3+4^. Treatment 2 +.Treatmen t5 1
Figure 2. The amount of nitrogen (N-mineral) in the first 30 cm of the soil 1997 (explanation legenda: see text).
72 A.R. 1997 Fruit Research Station
(amount aimed at maintainance of the organic matter content of the soil) the increase in storage was even lower: 90 kg/ha (also without loss of production). However when the nitrogen content of the soil sufficient is at planting the use of chicken manure pellets would lead to leaching of nitrogen as nitrogen is released very fast after application By aiming the amount of the applied organic resource at the organic matter requirement and by giving nitrogen fertilizer according to NBS or giving slow release fertilizers the surplus of nitrogen in the nitrogen balance can be reduced significantly without loss in production. This also holds for the use of chicken manure pellets.
The research in 1996 was partly funded by CIOM (Centre for Information and Promotion Manure applications)
Optimizing the water supply in relation to fruit quality and other aspects of apple and pear growing
M.P. van der Maas and M.C.J, op 't Hof
Because of the relationship between the soil water supply and growth it the application of water sometimes creates unnecessary growth problems. Anticipating on growth with the water application is only is not valid under wet soil conditions. Under dry conditions however much can be gained by adjusting the water application to the growht status of the tree and the water status of the soil.
Regrowth in 1997
In determining the water application one must not only take into account the fruit and ähoot growth (see annual reports of 1995 an 1996) but also the potential for regrowth if the shoots. From a pot trial from 1995 it became clear that the drier the soil the Tiore shoot growth was reduced but also the stronger regrowth was when the soil water supply was strongly increased in the beginning of august. When however the Dressure head of the soil water was maintained at a minimum around 45 kPa no significant regrowth was found after water application to a pressure head of 7 kPa. In a ield trial in 1997 this findings were affirmed. In a 20 year old pear orchard the egrowth varied from 25 till 43% depending on the water application in 1996 and 1997. The drought in 1997 started developing in the end of July followed by rain in the înd of august. Regrowth of the shoots manifested itself in alle treatments. The Jifference between treatment 1 and 2 was caused by water application in 1996: withholding water results in a lower growth potential over the years and thus also in a ower regrowth potential. The difference between treatment 2 and 3 can be explained jy the water application in 1997. The application started two weeks before the rain ell. The soil was already drying for three weeks while the moment of ending of growth was relatively short. Because of this the water application resulted probably in extra egrowth in comparison of the rain two weeks later. It was assumed that when the water application had been started earlier the regrowth would have been less than the
73 A.R. 1997 Fruit Research Statior regrowth of treatment 2. Regrowth decreases the flower bud production. Besides this regrowth increases the risk for mildew with apple and scab.
Requirements for the water status of the soil
Based on research to the effect of soil water supply on fruit en shoot growth, regrowtr of shoots and flower bud production requirements for the dryness of the soil are defined for two growing conditions: low and high fruit load. The dryness of the soil i; expressed in pressure head (10 kPa: soil is moist; 100 kPa: soil is relatively dry; 100C kPa: soil is very dry and tree dies). The requirements are shown in table 52 and refer tc average values for the whole rooting zone (parts with higher root densities hav« account proportionally more). When a strong stimulation of vegetative growth \: required the pressure head must be lower depending on soil texture (sandy soil: 5-1( kPa and heavy clay soil: 25 kPa).
How dry is the soil?
Besides the soil water requirements one must know the actual water status of the soi in order to determine the water application. One option is to use the compute progamme IRRY developed by FPO and Bodata for calculation of the pressure head ii the rooting zone. For the calculation meteorological data on global incoming radiation temperature and precipitation is needed. These can be easily obtained from the loca weather stations for the scab control when an extra light sensor is installed. Besidei this a dercription of the soil profile and the rooting zone and regular ground water leve measurements are needed. The pressure head calculations need to be checked twice i season by Watermark measurements. In 1997 IRRY was expended by a seperati calculation of soil evaporation and a differentiation of the water uptake over the rootinc zone based on root distribution and the posibility to perform the calculations for rootinj zones with wet and dry soil columns (e.g. for fertigation). The soil water pressure head can also be measured alone by Watermark. Then mon sensors are needed (the pressure head in all parts of the rooting zone must be known) one must measure at more moments (10 to 20 times per season depending on th< weather) and measurements need to be analysed to calculate the right wate application. Description of the soil profile is stil necessary. The amount of Watermarl sensors that are needed is depending on the spatial variability. For the planting year and the practice of root cutting and growing on ridges is n< version of IRRY available.
Table 51. Water application and reqrowth with Conference Treatment Water application in Regrowth 1997 1996 1997 (% of the shoots 1 no no 25 2 yes no 36 3 yes ves 43
74 A.R. 1997 Fruit Research Station
Table 52. Requirements for dryness of the soil (kPa pressure head) for apple and pear Fruit load May June July Auq. Sept. Oct. Low 50 50 30 30 50 70 Hiah 30 50 30 30 30 30
75 A.R. 1997 Fruit Research Station
Crop Protection
Testing of insectides, fungicides and bactericides in fruit growing
B. Heijne, R.H.N. Anbergen en W.A.G.M. Jansen
Application of Zolone-Flo to apple may be phytotoxic
B. Heine and R.H.N. Anbergen
Spring 1 996 WAs characterised by dry weather and temperatures below average. On e number of fruit farms phytotoxicity was reported after spray applications in May of thai year. The phytotoxic effect was associated with treatment of Zolone-Flo. Also the below average temperature was thought to be affecting the injury reported. It was said that tht injury was more severe as the temperature was lower during, or shortly after, the spra\ application. On the cultivars Golden Delicious, Jonagold and some summer varieties mor« injury was seen than on the cultivars Elstar, Cox's Orange Pippin and Belle de Boskoop The following research is actuated by the injury reported. The aim of the research is tc verify the phytotoxic effect of a Zolone-Flo treatment in the blossom period of apple anc to prove whether this effect is influenced by a low temperature and the cultivar under trial
In 1997 three trials were carried out. Two-year old trees, planted in pots, were grown ur. to full bloom in a greenhouse or in a growth chamber. When in full bloom severa concentrations of Zolone-Flo were applied to the trees. After the spray treatment a numbe of trees was kept under cold conditions for one night. In the the following two weeks th« leaves, petals, stamens and pistils were examined for signs of injury. In some of the treatments injury was seen. It was concluded that Zolone-Flo is sufficiently potent in potency to injure the leaves and flowers of apple under certain conditions. I appeared that the cultivar Cox's Orange Pippin was less sensitive to the treatment thar the cultivar Golden Delicious.The dosage of Zolone-Flo was not related to the amount o injury that occurred. In addition, the injury was not related to the cold treatment given t( the sprayed trees. The two lots of Zolone-Flo reacted in the same way.
It is hard to understand why the injury to the leaves and flowers of apple is not related t( the dosage of Zolone-Flo applied. One would expect a relation between dosage an( amount of injury. The lack of this relationship and the fact that for many years n< phytotoxicity of Zolone-flo to leaves and flowers of apple is reported, could indicate tha injury only occurrs due to a combination of factors. In this respect a combination of th( following factors may be of importance: A high susceptibility of the trees in times of rapid leaf development, when many new, ven susceptible leaves are present. A low relative humidity, both by day and night.
76 A.R. 1997 Fruit Research Station
Low temperatures A treatment of Zolone-Flo The results of the present tests do not indicate which factor is the most important.
Control of rust in plum caused by Tranzschelia pruni-spinosae var. discolor in 1996 and 1997
B.Heijne and R.H.N. Anbergen
Rust in plum is caused by the fungus Tranzschelia pruni-spinosae var. discolor. Brown pustules with spores on the under-side of the leaves and yellow spots on the upper-side are symptomatic of the disease. The diseased leaves drop early. In recent years rust in plum has been a recurrent problem. Chemical control of the disease is unknown. Therefore, n 1996 and 1997 atria l was carried out to test the efficacy of some fungicides. Some of the fungicides were tested in both years. Each trial was comprised of four treatments. The fungicides were applied three times. In The Netherlands no fungicide is allowed for control of rust in plum. Therefore, the fungicide treatments are indicated by a letter. In 1996 the first spray was applied on 27th June. The other sprays were applied at a weekly interval. In 1996 the third spray of all treatments was not applied, due to fruit russeting caused by fungicide treatment A esulting from the first two spray applications. In 1997 the tree sprays per treatment were applied at weekly intervals in July.
Ml the treatments resulted in a small, acceptable amount of visible residue on the leaves. Dn fruit the residue was hardly visible. The treatments did not cause any injury to the eaves. However, in 1996 treatment A caused considerable fruit injury, but only to that jart of the fruit actually hit by the spray. The injury was comprised of small and larger specks and even brown to black spots on parts of the fruit where the spray droplets were jried up. The larger spots were somewhat sunken. On the whole, the fruit skin gave an mpression of brown discoloration on a green background. Even after one application of :reatment A the symptoms were visible, but not so pronounced and not so black in discoloration. Unfortunately, in 1996 no rust symptoms occurred, not even on the jntreated trees. In 1997 treatment A was not repeated;th e other treatments did not cause any sign of phytotoxicity on leaves and fruit. In 1997 rust symptoms did occurr and on 9th September rust on leaves on long shoots was assessed by a rating from 0 to 3, in which ) = no symptoms; 1 = slight attack (<10% of leaves); 2 = moderate attack (10% - 50% of leaves); and 3 = severe attack (>50% of leaves). In Table 56 the average rating )er treatment is shown. Theleave s on the untreated trees were severely attacked by the rust fungus and early leaf Irop was extensive. The treatments were effective, but not significantly different from iach other. Contrary to the results in 1996, residue was hardly visible on the leaves in 1997. The ipplication of relatively large spray droplets in 1996, and with hardly any rainfall in the ummer of that year, has led to the visible residue.
77 A.R. 1997 Fruit Research Station
Table 56. Average rating of rust on plum leaves on 9thSeptembe r 1997 Treatment Rate (0 - 3) 1. untreated 2.7 b 2. B 1.3 a 3. C 1.6 a 4. D 1.4 a
LSD 0.06 0.5 F-test ** *
In 1996 treatment A was used in the trial because of a well-known effect on other rust fungi. However, the fruit russeting of the plum fruit was not acceptable. It is unclear whether this effect is due to the active ingredient or to the formulation of the product. In 1997 all three other fungicides were effective. In case of rust on plum, the correct timing of the spray applications is difficult. Two of the fungicides do have only a preventative action, whereas the third one does have a curative action too. Besides, the length of the infection period is unknown. In most years the rust symptoms on the leaves become visible after the pick of the fruit. However in some years most of the rust symptoms are already visible during picking. Therefore the sprays were applied well before the picking period, so as to allow a fair length of time before picking. Maybe in some years spray applications after the picking period are sufficiently effective. Such a spray scheme with effective fungicides does have a better chance of approval.
Biological control of diseases
B. Heijne and W.A.G.M. Jansen
Biological control of Botrytiscinerea in a belated strawberry culture
W.A.G.M. Jansen
The research was carried out in co-operation with the IPO-DLO institute at Wageningen Botrytis cinerea is the main fruit rot fungus. In practice, serious attack can result in a fruii loss of up to 30%. Several fungicides do have an approval for control of Botrytis ir strawberry. For some of these fungicides (the dicarboximides) a reduced efficacy iî reported. Demands for environmental safety of pesticides and high costs for pesticide development resuit in a restricted availability of new ones. At the same time the possibility of alternated use of different active ingredients diminishes and as a result the chance o fungal resistance to the fungicides increases. This gives reasonable ground for testinç alternatives of chemical control. Thus, biological control of Botrytis is a welcome alternative in sustainable strawberry growing. In the experimental garden at Breda the antagonistic effect of the fungus Ulocladiun atrium onBotrytis cinerea in strawberry was successfully tested, despite a rather low leve
78 A.R. 1997 Fruit Research Station of Botrytis attack. Regular spraying with the antagonist from planting time up to the end of blossoming was as effective in controlling Botrytis fruit rot as a routine spray scheme with Rovral/Eupareen. Applying the antagonist only in the blossom period was not effective.
Testing of insecticides and acaricides
New pesticides for control of codling moth, Cydia pomonella
.M.E. Schenk, H. Veijer and M.L. Joosse n integrated fruit growing in The Netherlands codling moth is controlled almost exclusively y the insecticides Dimilin (a.i. diflubenzuron), Nomolt (a.i. teflubenzuron) and Insegar (a.i. enoxycarb). Resistance of the codling moth to Dimilin has been reported from Spain and southern France. Locally in The Netherlands control of codling moth by Dimilin is not fable 57. Treatments for control of codling moth at Wilhelminadorp Mr. Treatment Active ingredient Dosage Application time I untreated Dimilin 480 g/L diflubenzuron 0.02% 5-7 days after the catch of the 1st moth in a feromone trap (= ± 50 - 70 degree days after the start of the flight, repeated application at a 3 weeks interval as long as the flight period continues). Product A Product B Product C Product D Gusathion- spuitpoeder 25% azinphos-methyl 0.15% 14-17 days after the catch of the 1st moth in a feromone trap (= ± 130 degree days after the start of the flight, repeated application at a 2 weeks interval as long as the flight period continues). Asepta Carpo- 6.7x1012 granulöse virusine virus/L 0.15% 14-17 days after the catch of the1 st moth in a feromone trap ( = ± 130 degree days after the start of the flight, repeated application at 2 weeks interval as long as the flight period continues).
79 A.R. 1997 Fruit Research Station adequate anymore. Besides several other explanations, reduced effectiveness of Dimilin is suspected. Therefore research was carried out to test other pesticides and control methods.
In 1997 one trial was carried out in the orchard of the Research Station at Wilhelminadorp and one in an orchard of a fruit grower at Lewedorp. In 1996 a high incidence of codling moth fruit injury occurred in both orchards: at Wilhelminadorp and at Lewedorp respectively there were >10% and >12% injured apples. In the orchard ai Wilhelminadorp, Dimilin has never been applied. In 1996 in the orchard at Lewedorp there was one application of Dimilin, one of Insegar and two of azinphos-methyl. In this orcharc at Lewedorp control of codling moth by Dimilin was not adequate in the last years. Each trial comprised of 8 treatments (see Table 57). The trials carried out conformed with the directives EPPO nr. 7 and PD 1 13. At Lewedorp product D in treatment 6, was replaced by an extra application of Asepta Carpovirusine at a dosage of 0.038% at the same application time as the product in treatment 8. The results in Table 58 show that the codling moth population at Wilhelminadorp is stil susceptible to Dimilin and control by that product was adequate. The other treatments were also effective at Wilhelminadorp, epecially the application of product D anc Gusathion-spuitpoeder. At Lewedorp Dimilin was not effective as in previous years. Aseptc Carpovirusine and product A were equally effective, but less so than the products B anc C and Gusathion-spuitpoeder. Gusathion-spuitpoeder and product C were equally effective Fruits were assessed for russeting of the skin and sorted in 4 classes: class 0 = no skir russeting, class 1 = up to 10% of the skin russeted, class 2 = 11-30% of the skir russeted, and class 3 = >30% of the skin russeted. An index of the russeting wa; calculated by the formula: Russeting index = class 0x1 + class 1 x3 + class 2 x5 + class 3 x7 The results are summarized in Table 59. It turned out that none of the treatments hadé negative effect on skin russeting.
Table 58. Codling moth fruit injury at picking time in % of number of fruits (inclusive dropped fruits) Treatment Wilhelminadorp Lewedorp untreated 3.9 c 18.7 e Dimilin 0.02% 0.5 ab 19.2 e product A 0.7 b 7.4 d product B 0.4 ab 3.9 bc product C 0.0.55 a abb 2.6 ab product D 0 a Gusathion spuitpoeder 0.15% 0 0 a a 1.8 a Asepta Carpovirusine 0.038% - 5.8 cd Asepta Carpovirusine 0.15% 0.3 ab 8.0 d
F-test M 1) ANOVA after transformation of values.
80 A.R. 1997 Fruit Research Station fable 59. Fruit russeting (index, see text) "reatment Wilhelminadorp Lewedorp jntreated 346 a 358a pimilin 0.02% 346 a 358a »roduct A 348 a 324a »roduct B 356 a 333a )roduct C 355 a 338a »roduct D 351 a Susathion spuitpoeder 0.15% 346 a 355a ksepta Carpovirusine 0.038% - 354a ^septa Carpovirusine 0.15% 345 a 337a
.SD 0.05 nc nc :-test ns ns n both trials the effect of the treatments on predatory mites has been investigated. The lumber of predators was counted before the treatment applications on 15th May and after he applications on 21thAugus t (Lewedorp) and 3rd September (Wilhelminadorp). In May he numbers were low at both locations and these did not differ significantly between the »lots. However, the second counting after the treatment applications did show distinct lifferences in numbers of predatory mites (Table 60). At Wilhelminadorp Gusathion puitpoeder had a negative effect on the population, whereas the products C and D timulated the growth of the population. At Lewedorp product A was the most harmful to he predatory mites, followed by Gusathion spuitpoeder. At Lewedorp in 4 out of the 5 ilots treated with Gusathion spuitpoeder rust mites and spider mites were present. The lew products B and C were not harmful to the predatory mites.
'able 60. Average number of predatory mites per 25 leaves at the second sample date reatment Wilhelminadorp Lewedorp ntreated 20 b 24 bed )imilin 0.02% 32 b 18 be roduct A 23 b 10 a roduct B 19 b 21 be roduct C 54 c 36 d roduct D 65 c ïusathion spuitpoeder 0.15% 12a 16 ab ^septa Carpovirusine 0.038% - 20 bc vsepta Carpovirusine 0.15% 32 b 27 cd
-test * * * ) ANOVA after transformation of values
81 A.R. 1997 Fruit Research Station
Number of moths versus week number
192 02 12 22 32 42 52 6 272 82 93 03 13 23 3 34
Figure 3. Number of codling moth caught in a feromone trap at Wilhelminadorp
Number of moths versus week number
192 02 12 22 32 42 52 62 72 82 93 03 13 23 33 4
Figure 4. Number of codling moth caught in a feromone trap at Lewedorp
82 A.R. 1997 Fruit Research Station he results show that the codling moth population at Wilhelminadorp is still susceptible to »imilin, probably due to the fact that Dimilin has never been applied in this orchard in the ast. At Lewedorp however, Dimilin was no longer effective, despite 5 applications at a iree weekly interval. The result of this trial confirms the suspicion that the effect of »imilin is reduced at several locations in The Netherlands. Dimilin is an important ïsecticide for integrated fruit growing. At locations with a reduced effect its role should e taken over by Asepta Carpovirusine. Besides, Asepta Carpovirusine has an advantage ver Dimilin in that is not harmful to earwings. On the other hand Asepta Carpovirusine as to be applied more frequently than Dimilin and that is not in the interest of fruit rowers. The results show that potentially the products B, C and D do fit into an itegrated pest control management. At least they were not harmful to predatory mites, owever, more research is needed to test their effects on the orchard fauna, before these roducts can be incorporated into the integrated pest control management. iology and control of apple scab
. Heijne and R.H.N. Anbergen esting of fungicides for a curative control of apple scab
spring the weather circumstances favourable for the apple scab fungus, Venturia wequa/is, are the main factor for the onset of a scab epidemic in commercial orchards, i the years 1993 and 1994 spring was characterized by long, wet periods. Besides other onditions, this prolonged wetness did result in a serious amount of scab in these years, l 1996 two new fungicides were approved for apple scab control in The Netherlands: cala (active ingredient pyrimethanil) and Score (active ingredient difeconazol). is claimed that these fungicides do have apreventativ e and curative action and therefore an be applied in a curative/preventative spay scheme. In 1996 the efficacy of both jngicides and some others was tested in atria l in which they were applied only after an ifection was recorded. The trial was carried out conforming to the directive EPPO nr. 5. pplications were made within 2-3 days after the scab infections. A minimum interval of ne week between the applications was taken into account, but for Score the minimum iterval was only 2 days. The fungicides under trial are summarized in Table 61. able 61. Fungicides under trial: name of product and active ingredient and application dosage roduct Active ingredient Dosage per 100 L ntreated water cala 40% pyrimethanil 75 ml core 10 WP 10% difeconazol 50 g
troby 50 WP 50% kresoxim-methyl 20 q
83 A.R. 1997 Fruit Research Station
Overview of infection data, according to Mills-3
Infections 2 17 22 25 8 11 2224 29 2 4 7 10
May June July
20 28 12 27 2' 9
Sprayings *) only sprayed with Score
Figure 5. Schematic time axis on which on the upperside the recorded infections are marked and on the underside the spray applications.
According to the Mety weather station no ascospore infections occurred in March an< April 1996. The first ascospore infection took place on 2nd May. Figure 5 summarizes ii a schematic way the ascospore infections and the spray applications. In all treatments ( sprays were applied, except for the Score treatment in which an extra spray was applie« on 2ndJuly . The first spray was applied on 4th May and the last one on 9th July. After th< trial period all trees were sprayed at a weekly interval with Captosan 83 WP at adosag i of 120 g per 100 L. To most of these Captosan applications Nimrod was added at dosage of 50 g per 100 L for control of powdery mildew. Results are summarized in Table 62 (leaf scab), Table 63 (fruit scab), and Table 64 (leave with powdery mildew). Upwards of 45% of the untreated leaves were scabbed. All treatments reduced the sea incidence significantly and more or less to the same extent. Only Score 10 WP was slightl less effective than the other products. All treatments reduced fruit scab incidence toe Also in this case differences in effect between the products were small, but signif.icam
84 A.R. 1997 Fruit Research Station able 62. Average number of sampled leaves per plot and the average leaf scab incidence on 14"1 June 1996 'reatment Number of sampled leaves % scabbed leaves ntreated 615 45.6 cala 618 0.7 a core 10WP 625 3.8 b 549 0.7 a 607 1.4 a 520 0.2 a troby 50 WP 612 1.7 ab
SD 0.05 2.0 test ** * able 63. Average number of sampled fruits per plot and the average fruit scab incidence on 17th July reatment Number of sampled leaves % Scabbed leaves ntreated 135 46.2 c cala 114 2.1 c core 10 WP 110 1.8 be 86 0.7 abc 159 0.4 ab 129 0 a troby 50 WP 88 0.3 ab
SD 0.06 1.6 test « ** *
able 64. Incidence of leaves with powdery mildew on 14th June reatment % leaves with powdery mildew ntreated 30.2 cala 22.5 core 10 WP 5.9 14.5 23.3 c 29.4 c troby 50 WP 7.3 ab
5D 0.05 7.8 test * * *
severe incidence of powdery mildew, caused by Podosphaera leucotricha, occurred in e trial field. Assessments were made on 14th June. Upwards of 30% of the untreated
85 A.R. 1997 Fruit Research Statior leaves were attacked by powdery mildew. The treatments with Score 10 WP, Stroby 5 WP and product A were effective.
The weather in the spring of 1996 was extremely dry. It is very rare that ascospor infections of scab do not occur in March and April. The infections at the end of May wer the main cause of the onset of the scab epidemic. In general, 1996 was a year in whic scab could easily be controlled. Trees in the untreated plots had only 46% leaf sea incidence in June and that is rather low for the time of the year. Due to this low incidence difference in curative efficacy between the products could hardly be measured. May b the relatively cool temperatures at the end of May have caused Score 10 WP to b somewhat less effect towards leaf scab. Contrary to this the effect of Scala on fruit sea seems to be somewhat less good. The same experience was met in Belgium. Stroby 5 WP is thought to be a fungicide with only a preventative action on spore germination, fi a later stage Stroby 50 WP also checks the production of conidia. Between some of the applications rather large intervals occurred: up to 16 days in th period 4th to 20th May. In these 16 days three new leaves per long shoot were producec The youngest one had definitely no fungicide residue on its surface. Thus it can b concluded that the infections on 17th May could only be controlled curatively. Duet o the fact that in 1995 no fungicides were applied for control of powdery mildew an in 1996 the first spray for control of this disease was applied mid-July, the infectio pressure was very high. Besides, in 1996 the weather circumstances were very favourab for powdery mildew attack. Product A did control powdery mildew to some extent. N specific mildewcide was tested. It is assumed that the fungicides under trial gave on moderately control of powdery mildew.
Development of a propagation and production culture of strawberr in the open without chemical soil disinfection
W.A.G.M. Jansen
Crop rotation of strawberry and Tagetespatula (African marigold) for control of tr nematode Pratylenchus penetrans
Injury thresholds for Pratylenchus penetrans in a three month' culture of strawberry fric plants must be at a higher level than 20 nematodes per 100 ml sandy/loam soil or ths 212 nematodes in 10 gram root mass. These amounts of Pratylenchus penetrans at tf start of a trial did not reduce the production in a three month culture of strawberry fric plants in two consecutive years on the same field in the absence of chemical sc disinfection, and despite an increase of the nematode population in these two years.
If chemical soil disinfection is no longer allowed, problems with notably the nematoc Pratylenchus penetrans can be expected in modern culture of strawberry on sandy soil It is well-known that Tagetes patula reduces the population of Pratylenchus penetran Thus, crop rotation with strawberry and Tagetes patula is an attractive alternative fi chemical soil disinfection. The question is how long the Tagetes crop has to be grown
86 A.R. 1997 Fruit Research Station he field for an effective control of the nematodes. Besides, the earliest and latest possible owing date in view of the planting time of the strawberries, has to be known. In 1996 rials were started in which the effect of late sowing dates on nematode population levelopment was tested in combination with the duration of the culture. In 1997 these rials were extended to testing the effect of early sowing dates in combination with the luration of the culture. owing in August 1996 resulted in a fair amount of Tagetes crop. However, that crop loted only 20-25 cm in depth, whereas the root zone of strawberry is on average 40 cm depth. Sowing Tagetes in September definitely does not results in a full-grown crop; lese plants rooted only 5-8 cm in depth. Sowing in early spring 1997 (March and April) Iso did not result in a full-grown Tagetes crop. These plants had to be covered for rotection against night frost in mid-April. Unfortunately that protection by acove r of agryl loth failed and the Tagetesplant s were killed by the frost. Besides, the protection of the lants by cloth at an early stage prevented the application of a herbicide and as a result fair amount of weeds were grown between the Tagetesplants . At later sowing dates in 997 the Tagetes plants grew well and gave a good crop and root mass. i three month' culture of Tagetes in the autumn of 1996 (August-October) reduced the evere soil infestation by Pratylenchus penetrans (179 nematodes per 100 ml soil) to a ery low level (2 nematodes per 100 ml soil). However, sowing later than in August can suit in a variable amount of crop, depending on the weather circumstances. Late in utumn, growth retards and besides, Tagetes is very susceptible to frost injury.
l 1997 a three month' growth of Tagetespatu/a in the spring (May-July) reduced the opulation of Pratylenchus penetrans from 85 per 100 ml soil to 5 per 100 ml soil. A two ïonth' growth in the spring (June-July) reduced the population from 58 per 100 ml to 0 er 100 ml. Due to the large variation in nematode density per soil sample only the general onclusion can be drawn that a Tagetes crop grown for 2-3 months in spring is capable f reducing the nematode population to an acceptable low level.
iology and control of canker
Heijne and R.H.N.An berg en
ontrol of canker on apple (caused by Nectriagalligena) b y a combination of fungicide jplications and chemically induced accelerated leaf drop in 1995 and 1996
preceding years it was proved that application at the onset of leaf drop of Ca-chelate Ethrel accelerates this leaf drop. A combination of an acceleration of the leaf drop and )plication of fungicides may result in an improved control of canker, caused by Nectria illigena. In theory this improvement could be achieved by a shorter period in which leaf :ars susceptible to infection are present. In this shorter period the leaf scars can better i covered up with fungicides
87 A.R. 1997 Fruit Research Statior
Prunings with sporulating cankers were hung in the top of the trees before the start of th leaf drop as infection sources and these cankers stayed there during the leaf drop perioc Fungicide sprays were applied at 10% leaf drop stage either combined or st combine with Defoliant (10% Ca-chelate). The second application of the fungicides took place s the stage of 90% leaf drop. To all sprays a surfactant (0.1% Agral LN) was added Th trial was comprised of 16 treatments and these were applied in both the autumn of 199 and 1996 to the same trees. The number of cankers was counted in June 1996 and i May 1997. After the first spray application at 10% leaf drop this leaf drop was speeded up in thos plots where Defoliant had been applied. The progress of the leaf drop was assessed in i plots of the trial field and the average percentage of leaf drop per treatment in Novembi 1995 is summarized in Table 66. Due to differences in leaf drop progress, the date c which the second fungicide spray was applied differed for the distinct treatments.
Table 65. Apple canker control treatments: products, active ingredients and dosac Code Product Active inqredient Dosaqe per 100 L 0- untreated water - 0 + untreated + Defoliant Ca-EDTA(10%) 2000 g TL- Topsin-M low thiophanate-methyl 25 ml TL + Topsin-M low + Defoliant thiophanate-methyl 25 ml + 2000 g TH- Topsin-M high thiophanate-methyl 100 ml TH + Topsin-M high + Defoliant thiophanata-methyl 100 ml + 2000 g CL- Captosan low captan 62.5 g CL + Captosan low + Defoliant captan 62.5 g + 2000 g CH- Captosan high captan 250 g CH + Captosan high + Defoliant captan 250 g + 2000 g DL- Delan low dithianon 12.5 ml DH- Delan high dithianon 50 ml KHL- Funguran-OH low copper hydroxide 200 g KHH- Funguran-OH high copper hydroxide 300 g at 1st; 500 at 2nd KOL- Brabant Koperoxychloride 50% WP copper oxychloride 200 g low KOH- Brabant Koperoxychloride 50% WP copper oxychloride 300 g at 1s'; 500 hiqh at 2nd
Table 66. Averaqe % leaf drop n November 1995 after the first spray application Treatment code Date 0- 0+ TL- TL+ TH TH+ CL- CL + CH- CH+ S- S + 12 14 45 27 44 26 70 31 69 22 67 7 15 20 30 82 46 84 49 91 45 88 39 92 34 48 27 79 100 90 100 92 100 90 100 87 100 76 94 29 - . - 82
88 A.R. 1997 Fruit Research Station t is remarkable that both Captosan and Topsin-M, applied without Defoliant, accelerated the leaf drop to some extent in comparison with untreated (water). As expected, 2% Defoliant, on its own and in combination with afungicide , accelerated the leaf drop by far Tiore. Remarkably: Topsin-M, but not Captosan, at a low dosage in combination with Defoliant accelerated the leaf drop less than Topsin-M at a high dosage.
Fable 67. Effect of treatments on cankering, expressed as average number of cankers, excluding those directly under the inoculum source M Dode Treatment June 1996 Mav 1997 0- untreated 7.2 d 16.3 cd D + untreated + Defoliant 7.7 cd 21.5 d 1"L- Topsin-M low 3.2 bed 9.8 abc rL+ Topsin-M low + Defoliant 3.0 ab 9.3 abc m- Topsin-M high 1.2a 6.3 a FH + Topsin-M high + Defoliant 1.3 a 5.0 a :L- Captosan low 3.7 abc 8.0 ab :L+ Captosan low + Defoliant 3.2 ab 7.0 ab 3H- Captosan high 4.2 bed 7.5 ab 3H+ Captosan high + Defoliant 2.7 abc 9.2 abc 3- 1s' Score - Defoliant; 2nd Topsin-M 4.3 abed - 3 + 1s' Score + Defoliant; 2nd Topsin-M 2.1 ab - DL- Delan low 2.3 ab 10.3 abc DH- Delan high 4.2 bed 13.8 bed CHL- Funguran-OH low 3.2 ab 7.2 ab CHH- Funguran-OH high 3.3 abed 6.0 a COL- Brabant Koperoxychloride low 1.8 ab 5.7 a COH- Brabant Koperoxvchloroide hiqh 5.0 bed 6.7 ab Statistics: one-factorial ANOVA
Theresult s of the treatments on cankering are summarized in Table 67. The cankers direct jnder the inoculum were excluded from the countings, because in that part of the tree all ontrol failed. Presumably the infection pressure was too high in that part of the tree and herefore the number of cankers was not related to the treatment. The other cankers were nore scattered over the tree as in an orchard under normal circumstances with low noculum pressure. both years more cankers were present in trees that did not receive a fungicide ipplication in autumn. Differences in cankering between the fungicide treatments were ow, although in trees systematically treated with Topsin-M the number of cankers was ower than in the trees treated with any other fungicide. For a better interpretation of the esults a two-factorial ANOVA was carried out and the results of this arrangement are ummarized in Tables 68 and 69. he results in Table 68 show that application of Defoliant has no effect on cankering, xcept for the combination with Score in the first year. In the first year Topsin-M in the ligher dosage was more effective than Captosan. In the second year the application of )elan resulted in more cankering than the application of the other fungicides (Table 69).
89 A.R. 1997 Fruit Research Station
The acceleration of the leaf drop by an application of Topsin-M or Captosan, both withou Defoliant, is not accompanied by leaf scorching. In practice this phenomenon o acceleration of the leaf drop is never noticed, despite the broad use of Captosan ii summer and of Topsin-M in the autumn. The underlying mechanism is unknown. Tha mechanism should also explain why the higher dosage of Topsin-M, but not that o Captosan, effects the acceleration more than the lower dosage.
Table 68. Effect of Defoliant on cankering, expressed as average number of cankers excluding those directly under the inoculum source M + Defoliant Defoliant May 1997 untreated 11.5 e 9.8 de 18.9 c Topsin-M low dosage 4.3 ab 5.8 bed 9.6 b Topsin-M high dosage 3.8 ab 2.2 a 5.6 a Captosan low dosage 5.8 bc 6.2 bed 7.5 ab Captosan high dosage 5.3 bc 6.7 bed 8.3 b Score 3.9 ab 7.9 ede -
F-test (after root transformation): fungicide ** * ** * Defoliant ns ns interaction ** * ns M Statistics: two-factorial ANOVA, as factors fungicides with or without Defoliant
Table 69. Effect of fungicides on cankering, expressed as total number of cankers excluding those directly under the inoculum source 1) Delan Topsin-M Captosan Funguran- Brabant OH koper- oxychloride 16.9 b 12.1 a 11.6a 9.4 9.8 a
F-test (after root transformation): fungicide dosage ns interaction ns ') Statistics: two-factorial ANOVA
In the spring of 1997 significantly more cankers developed than in the spring of 199' (Table 67). Presumably the extremely dry autumn and winter of 1995/96 was not ver favourable for infection. The fact that the lower dosage of the fungicides applied in 199 was hardly less effective than the higher dosage, underlines this view. Besides, interactio occurred between fungicides on the one hand and dosage on the other. Despite the higher incidence of canker in 1997, the fungicides hardly differed in the effect. Differences in dosage effect did not occurr. Maybe due to a high infection pressur in the autumn of 1996 the higher dosage of each of the fungicides still was not effectiv enough. Apart from that, as expected, Delan was less effective than the other fungicide
90 A.R. 1997 Fruit Research Station
,nth e autumn of 1996. Already research at Gorsem, Belgium and past research by J.F. van Dijke in the centre of The Netherlands shows that Delan was less effective on canker than or instance captan. t seems that the effectiveness of Funguran-OH (copper hydroxide) does not differ from hat of copper oxychloride. This is contrary to results obtained by Graf (1985) in Germany, n his trials copper hydroxide was more effective on canker than copper oxychloride. 3robably the amount of copper ions is decisive for the effectiveness. The percentage of :opper ions in Funguran-OH and in Brabant Koperoxychloride are similar: respectively 32 and 29. Despite the leaf drop acceleration by Defoliant in both years, the amount of cankering was lot reduced. Maybe the timing of the different fungicide spray schemes is to be blamed or that. The fungicide application at 10% leaf drop stage covered the leaf scars present it that time. Due to the effect of Defoliant on the leaf drop process, indeed the second ipray was applied earlier than normal, but maybe still came too late to prevent all leaf icars being infected. Dnth e other hand it is true that in all treatments 100% leaf drop was achieved in more >rles s the same time. Thus, the total length of the leaf drop period was not shortened by Defoliant, but relatively more leaves dropped in the first days after the application and the everse was true at the end of the leaf drop period.
Biological control of strawberry diseases
N.A.G.M. Jansen
Jiological control of powdery mildew in a belated strawberry culture n strawberry growing powdery mildew can result in a reduction in plant growth and, as i resul,t in crop loss. Warm weather favours the growth of the pathogen. Demands for mvironmental safety of pesticides and high costs for pesticide development result in a estricted availability of new ones. At the same time the possibility of alternated use of lifferent active ingredients diminishes and as a result the chance of fungal resistance to he fungicides increases. These are reasonable grounds for testing alternatives of chemical ontrol. Thus, biological control of powdery mildew is awelcom e alternative in sustainable trawberry growing. In 1997 a trial was set up to test the effectiveness of some liopesticides for control of the disease. Unfortunately powdery mildew did not occur in the rial field and therefore the effectiveness of the biopesticides could not be judged.
biological control of pests in strawberry and bush and cane fruits
V.A.G.M.Jansen
ampling methods for thrips in a belated culture of strawberry under glass
l strawberry growing thrips do injure the fruit and this can result in a considerable loss f crop.In open flowers thrips feed on the receptacle and at a later stage on the fruits too.
91 A.R. 1997 Fruit Research Station
Average number per blue and yellow catch plate versus data
28/8 4/9 11/9 18/9 25/9 3/10 9/10 16/10 23/10 30/10 6/11
1 = thrips blue 2 = thrips yellow
Figure 6. Development of the thrips population in 1997 measured by catch plates astrap .
Average number of thrips, predator mites and predator bugs per flower versus data 10 9
28/8 4/9 11/9 18/9 25/9 3/10 9/10 16/10 23/10 30/10 6/11
1 = thrips 2 = predator mites 3 = predator bugs
Figure 7. Development of the population of thrips and natural ennemies in flowers i 1997. Flowers are beaten in the hand
92 A.R. 1997 Fruit Research Station
Average number of thrips, predator mites and predator bugs per flower versus data
10
9
28/8 4/9 11/9 18/9 25/9 3/10 9/10 16/10 23/10 30/10 6/11
1 = thrips 2 = predator mites 3 = predator bugs
igure 8. Development of the population of thrips and natural enemies in flowers in 1997. Flowers are dipped in alcohol ks a result the fruits bronze. The development of a thrips population is tracked by ountings of thrips on blue coloured catch plates. This method gives no information on the opulation of natural ennemies of thrips. A trial was set up to test several sampling lethods for both thrips and natural enemies. It is hoped to find a sampling method that ives a quick insight into the development of the population of thrips and natural enemies, o that corrections can be made in good time for control of the insect pests, hunting of thrips in flowers after dipping the flowers in alcohol (Figure 8) gives an insight ito the population development comparable to that by counting thrips on blue and yellow atch plates (Figure 6). Counting thrips in flowers after beating the flowers in the hand oes not give such a good insight into the population development (Figure 7). Regular ounting thrips in flowers after dipping the flowers in alcohol gives an earlier insight into ie population development than counting thrips on plates. Besides, dipping flowers in Icohol gives insight ito the population development of the predatoty mite Amblyseius cucumeris and the redatory bug Orius. It is remarkable that the yellow plates caught more thrips than the lue ones. Maybe this is due to the fact that the main part of the population was tobacco irips. Californian thrips are more attracted by blue catch plates. Unfortunately no ilationship could be established between numbers of thrips and crop injury, because no jury was noticed.
93 A.R. 1997 Fruit Research Statior
List of chemicals
Trade name Common name
Growth Regulators Amid Thin 8.4% a-naftylacetamide (NAAm) ATS (ammoniumthiosulphate) 99-100% pure powder BAS 125 10W 10% prohexadione-Ca D4017 10% benzyladenine Fruitone NA 100 g/l oc-naphthylacetic acid (NAA) Pommit Ekstar 110 SL 8% K-salt NAA + 3% urea Sevin SL 480 g/l carbaryl Tween 20 (wetter) Polyethylene sorbitan monolaureate
Fungiciden en Herbiciden 2,4D 2,4D Brabant Koperoxychloride 50% koperoxychloride Captan sp 83% WP 83% captan Delan flowable 750 g/l dithianon Diuron 80% diuron Exact 50 g/l triadimenol Eupareen spk 50% tolylfluanide Finale 200 g/l glufosate Funguran-OH 50 WP 50% koperhydroxide Gusathion sp 25% azinfos-methyl MCPA MCPA Pallitop 37% nitrothal-isopropyl Pirimor 50% pirimicarb Roundup 36% glyfosate Scala 400 g/l pyrimethanil Score 10% difenoconazol Simazin simazin Spruzit 40 g/l pyrethrum Stroby WG 50% kresoxim-methyl Topsin M sp 70% thiofanate-methyl Topsin M fluid 500 g/l thiofanate-methyl
Insecticiden Asepto Carpovirusine Cydia pomonella granulosevirus Delfin Bacillus thuringiensis Dimethoaat 400 g/l dimethoaat Dimilin sp 25% 20% diflubenzuron
94 A.R. 1997 Fruit Research Station
Cilval 400 g/l vamidothion *AK3+ 4 feromoonverwarring fruitmot/bladroller 1AK 4 250 mg 2-11-tetradecenylacetaat Jndeen 50% propoxur 'oione-Flo 500 g/l fosalone
95 A.R. 1997 Fruit Research Statioi
List of Entries
Apple - X6690 - clones/mutants 45 - Zuzana - cultivars 37 - diseases 7! - 21-69 - canker 8 - 11W-12-11 - mildew 8 -A 933/190 - scald 40,8 - Ahra - pollination 3 - Ahrista - regrowth 7 - Aurin de Bistrita - rootstocks 1 - Baugêne -AR 10.2.5 - BN 26/261 -C 6 - BN 32/41 - M.9 -Celeste (Delcorf Schuhmann) - M.27 - Cox's Van Bemmel - MAC-39 -CPRO 88022-A-13 - Mark -CQR10T17 - P.2 -CRR1T73 - P.22 - Creston -P.59 - Cwastresse - P.60 - D:0106 -P.81 - DCABO 81.417.002 -P.92 - DCABO 81.417.016 - Supporter 4 (Pi 80) - Delearty - V 605-1 - Delgobel - V 605-3 - Deloran - Voinesti 1 - Denar - Voinesti 2 - Double - taste test 4 - E 55/52 - water supply 7 - FAW7167 Blueberry - Jarka - cultivars 6 - Katka - delayed harvest 6 - Marina - fertilization 6 - McShay Canker 8 - NPV-1 Cherry (see Sweet cherry) - NY 632 Cultivars -NY 65707-19 - apple 3 - NY 75441-67 - blueberry 6 -PX 9176 - cherry 5 - Reinette de Blenheim - pear 4 - Shampion - plum E - Slovakia
96 A.R. 1997 Fruit Research Station
- strawberry 54 - BP 9667 - quincelCycron/a oblong a) 16 - Diana Diseases - Erika - strawberry 86,91 - Etrusca - apple 76 - Giolu - canker 87 - HW614 - mildew 85 - HW 616 - scald 40,83 - HW617 - plum - HW 620 - rust 77 - ISF 80.51.72 Economics - ISF 80.66.82 - integrated fruit growing 63 - ISF 80.108.72 - root pruning 64 - ISF 84.3262.40 Environment - ISF 84.3336.40 - nitrogen 69 - Nitra Fertilization -Vila - strawberry 69 - production 49 - cow manure - regrowth 73 - slow release fertilizers - rootstocks 14 - GFT-compost - BA 29 Flowering 8 -C.132 Fruit thinning (see Thinning) - Kwee MC Fruit quality 19 - OHxF 333 (Brokmal) Fruit russeting -OH 11 - Delblush 33 -OH 20 Fungicides 76 -OH 33 - Nectria galligena - taste test 49 - Podosphaera leuctrich - tree form 21 - Tranzschelia pruni-spinosae Pesticides 76 var. Discolor - Captosan Venturia inaequalis - Delan 3rowth regulators (see also Thinning) 19 - Funguran-OH apple - Koperoxyhloride pear - Scala Hazelnut 16 - Score nsects - Stroby Cydia pomonella 79 - Topsin-M -ight perception 19 Mildew 85 - Dimilin Nematodes (see Pratylenchus - Carpovirusine penetrans) 86 - Gusathion Dptimum harvest date 65 - Zolone flo ear cultivars 47 - azinfos-methyl - Beurré Kustendil - captan - BP 9292 - diflubenzuron
97 A.R. 1997 Fruit Research Station
- difenoconazol - Agvambari - dithianon - Balady Awad - fosalone - Bencikli - koperhydroxide - Bourgeault - koperoxychloride - BQ 6-35 - kresoxim-methyl - Ekmek - pyrimethanil - Gukuz Gobeke Pests - 1/18 - apple - 1/21 - codling moth 79 - I/30 Planting density 23 -I/50 - apple - Leskovacka - Golden Delicious - Morava - Jonagold - Rea's Mammoth Planting system 17 - Ronda - apple - Sobu - cherry - Vranja - pear Root pruning 21 Plum 50 Scald 40,82 - cultivars Storage - Elisa - Delblush/Tentation® 6: - lalomita - Santana 6£ - Silvia - optimum harvest time 69 - V72521 - mutants - Violetta - cultivars 6E - WJ63 - apple - rootstocks 15 - Ahrista - Ferlenain - Braeburn - Hollywood - Braestain - Ishtara - Delbuena - Jaspi - Delmoip - Marianna 2624 - Golden Delicious - Marianna GF8-1 - GoldRush - Myruni - Topaz - P 8-13 - blueberry 6i - Prunus blireana - cherry 65 - Prunus dasycarpa - pear 6! - Reine Claude Strawberry - St. Julien A - biological control 9 - VVA-1 - cultivars rust 77 - Elsanta selections 5! Pollination/Self pollination 34 - everbearers 5- Pratylenchus penetrans 86 Sweet cherry Precipitation 7 - cover 2 Quince (Cydonia oblonga) 16 - cracking 2: - cultivars - cultivars 5i
98 A.R. 1997 Fruit Research Station
- 13S-49-24 Tree form - Adriana - pear 21 - Botond - sweet cherry 21 - Colney /GM.9 Thinning - Hartland - apple 26 - Karina (kas) -ATS - Kordia /GM61/1/1 - Amid-Thin - Kordia /W158 - carbaryl - Kozerska - D4017 - Lapins - Ethrel A -J.I. 11.343 - NAA - Na 12/21 - NAAm -Na 18/27 - Sevin SL - Nadino pear - Newstar -ATS 29 - Oktavia (kas) - D4017 - Ruby - Fruitone-NA - Salmo - NAA - Sam /Edabriz Walnut 16 - Sam /GM.61/1/1 Watersupply - Sasha /GM.9 - apple 73 - Sel. V. d. Ende - mildew - Somerset - regrowth - Star - IRRY - Starking H.Giant pear 73 - Summit /GM.9 - regrowth - Sunburst - scald - Sweetheart - Watermark - Sylvia - Techlovan - Techlovan (kas) - V 69062 -V 690618 - Vernon -Vit 2.14.91 -Vit 4.9.91 -Vit 7.1.91 -Vit 4.8.91 - Vittoria - fruit weight 21 - harvest time 52 - minerals 22 • taste 22 - tree form 21 ragetes 86 remperature 7
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Publications
Awad, M., A. de Jager and L. van Westing - Het beste van de appel wordt vaak weggegooid. (The best part of the apple is öfter throwing away) Fruitteelt 87(1997)27:14-15
Balkhoven-Baart, J.M.T. - ATS beloftevol dunmiddel voor pruimen. (ATS, a promise for plums) Fruitteer 87(1997)13:14-15 - ATS een nieuwe bloemdunner voor Elstar. (ATS a new thinning agent for E/star Fruitteelt 87(1997)16:12-13 - Schurftbestrijding in het najaar werkt. (Scald control in autumn is successful) Fruit teelt 87(1997)41:8-9
Balkhoven-Baart, J.M.T. and Th. Veens - Spuiten van dunmiddelen heeft voorkeur. (Spraying new chemical thinners preferable Fruitteelt 87(1997)16:14
Balkhoven-Baart, J.M.T. and S.J. Wertheim - Toelating nieuwe dunmiddelen moeilijk. (Admission new chemical thinners difficult Fruitteelt 87(1997)16:11. - Results of trials with the growth regulator Lex 8989 on apple and pear. Intern Versla« FPO Wilhelminadorp, november 1997: pp.8 - Thinning response of Elstar apple to the flower thinner ammoniumthiosulphate (ATS) Acta Horticulturae 463 (1997):481
Besseling, P.A.M. and M.L. Joosse - Biologisch fruit professioneel geteeld. (Biological fruit grown professionally) Fruitteel 87(1997)20:18-19 - Hoge prijzen noodzakelijk voor biologische fruitteelt. (High prices necessary fo biological growing fruit) Fruitteelt 87(1997)20:20
Bloksma, J. and P.J. Jansonius - Andere schimmels in schurftresistente rassen. (Other fungi in scald resistant cu/tivars Fruitteelt 87(1997)22:16-17
Blommers, L. - Feromoonverwarring eindelijk toegelaten. (Pheromone disruption finally admittec Fruitteelt 87(1997)17:16-17 - Fruitmotvirus voor degelijke biologische bestrijding. (Codling moth virus for biologia control) Fruitteelt 87(1997)20:12-13 - Teeltmaatregelen alternatief voor spuitvrije zones. (Growing measures alternative fc non-spraying zones) Fruitteelt 87(1997)49:10-11
100 A.R. 1997 Fruit Research Station
îootsma, J. 1997 het slechtste jaar in de rij. (1997 the worst year in row) Fruitteelt 87(1997)27:12-13 Boskoop sterker dunnen. (Boskoop need a stronger thinning) Fruitteelt 87(1997)16:19 Een vroege chemische vruchtdunning helpt. (An early chemical thinning helps) Fruitteelt 87(1997)16:18-19 Meer onderzoek nodig voor gedegen advies. (More research necessary for a good advice) Fruitteelt 87(1997)16:24-25 Onverwachte effecten bij dunning. (Unexpected effects with thinning) Fruitteelt 87(1997)16:18 Peren vroeg in productie. (Pears early in production) Fruitteelt 87(1997)2:12-13 Plantmateriaal: meer kiezen voor kwaliteit. (Plantmaterial: better choose for quality) Fruitteelt 87(1997)50:8-9 Smalle slanke spil vraagt goede start en verzorging.(Thin slender spindle asks for a good start and nursery) Fruitteelt 87(1997)1:20-21 Vroege bloei gunstig voor vruchtmaat. (Early bloom good for fruit size) Fruitteelt 87(1997)16:15
Drabbels, J.G. and M.J. Groot, Effect wortelsnoei verschilt per ras - FPO-onderzoek naar economische aspecten van wortelsnoei. (Results root pruning vary per cultivar - FPO-research for economical aspects of root pruning) Fruitteelt 87(1997)42:12-13
îroot, M.J. M.9 niet altijd de beste keuze - FPO-onderzoek naar economische aspecten onder stammenkeuze. (M.9 not always the best choice - FPO-research into the economical aspects of rootstocks) Fruitteelt 87(1997)19:18-19
3root, M.J., M.L. Joosse and P.A.M. Besseling Plantdichtheden en onderstammen economisch bekeken. (Economical aspects of planting densities and rootstocks) Fruitteelt 87(1997)1:18-19 KWIN goed te gebruiken in de praktijk - FPO en IKC-Landbouw geven een nieuwe Kwantitatieve Informatie Fruitteelt uit. (FPO and IKC publish a new Quantitative Information (KWIN)) Fruitteelt 87(1997)8:10-11
îroot, M.J. and A.M.E. Schenk Gangbaar MBT lijkt bij gelijke prijzen het beste - FPO-onderzoek naar economische aspecten van bedrijfssystemen. (Current fruit growing seems the best at equal prices - FPO-research into the economical aspects of various crop protection systems) Fruitteelt 87(1997)36:14-15
leijne.B. and R.H.M. Anbergen Bladvalversnelling geen voordeel bij kankerbestrijding. (Leaf abscission no benefit with canker control) Fruitteelt 87(1997)34:20-21
101 A.R. 1997 Fruit Research Station
Heijne, B. , R.H.M. Anbergen, J.M.T. Balkhoven-Baart and Th.S.G.M. Veens - Schurftbestrijding in het najaar werkt.(Scald control in autumn successful) Fruitteelt 87(1997)41:8-9
Jager, A. de and J. Blaszczyk - Vruchten aan meerjarig hout zijn het langst te bewaren. (Fruit on old wood can be stored longer) Fruitteelt 87(1997)26:12-13
Jansen, W.G.A.M. - Mogelijkheden voor oogstspreiding blauwe bes. (Possibilities for different harvest times bleuberry) Fruitteelt 87(1997)6:16-18 - Rijprot aanpakken vanaf bloei tot pluk. (Ripe rot control from bloom till harvest) Fruitteelt 87(1997)18:14-15
Jansonius, P.J., J. Bloksma, B. Heijne and R.H.M. Anbergen - Infectiedruk beperken met schaar, frees en zaag. (Infection control with pruning shears, rotary cultivator and saw) Fruitteelt 87(1997)40:10-11
Joosse, M.L. and M.J. Groot - Hazelnoot: alternatief met kanttekeningen - FPO-onderzoek naar economische perspectieven van hazelnoten. (Hazelnut: alternative crop with side-notes - FPO research into the economical aspects of hazelnuts). Fruitteelt 87(1997)47:22-23
Kemp, H. - FPO-onderzoek naar nieuwe pruimenrassen. Pruimenrassen voor de praktijk. (FPO research on new plum cultivars. Plum cu/tivars for practical growing) Fruitteeh 87(1997)34:16-18.
Kemp, H. and M.C.A. van Dieren - FPO-onderzoek naar rassen van appel. Het nieuwe is beter, maar niet altijd (1). (FPO research on apple cu/tivars. The new ones are better, but not always) Fruitteeh 87(1997)1:13-15. - FPO-onderzoek naar mutanten van appel. Het nieuwe is beter, maar niet altijd (2) (FPO-research on apple mutants. The new ones are better, but not always) Fruitteel 87(1997)1:16-17. - FPO-onderzoek naar rassen van peer. Oude rassen moeilijk te overtreffen. (FPO research on pear cu/tivars. The old cu/tivars are hardly to beat) Fruitteel 87(1997)2:10-11.
Koeken, J.P.G., S.J. Wertheim and E.A.M. van Remortel - Bloemdunning van 'Elshof' met ATS. I. Invloed van temperatuur en relatieve lucht vochtigheid. (Flower thinning of 'Elshof" with ATS. I. Influence of temperature ant relative air humidity) Intern Verslag FPO Wilhelminadorp, augustus 1997 :pp.11. - Bloemdunning van 'Elshof' met ATS. II. Invloed van relatieve luchtvochtigheid bi normale bloeitemperatuur. (Flower thinning of 'Elshof" with ATS. II. Influence o relative air humidity with normal flower temperature) Intern Verslag FPO Wilhelmina
102 A.R. 1997 Fruit Research Station
dorp, augustus 1997: pp.11.
Maas, M.P. Van Watergeven kan problemen oplossen én veroorzaken. (Water applications can solve and create problems) Fruitteelt 87(1997)11:1 8-20
Maas, M.P. van and M. op 't Hof Efficiënt onigaan met stikstof. (Effecient use of nitrogen) Fruitteelt 87(1997)46:20,21
Meijer, R.J.M. Eufrin, stimulator van samenwerking in Europees fruitonderzoek. (Eufrin, stimulator of co-operation in European fruit research) Fruitteelt 87(1997)8:14-15 Fruitteeltpraktijkonderzoek in ander vaarwater. (Fruit research in another berth) Fruitteelt 87(1997)35:16-17 FPO Randwijk groeit gestaag. (Randwijk grows steadily) Fruitteelt 87(1997)35:18
Nieuwkoop, P. van LEI-DLO herziet voorspelde resultaat. (LEI-DLO reviews predicted result) Fruitteelt 87(1997)23:12-13
FJoelofs, F.M.M.P. Bewaring kersen biedt perspectieven. (Storage of cherries opens new perspectives) Fruitteelt 87(1997)6:10-11 Schilkwaliteit lijkt sleutel voor oplossing schilvlekjes. (Quality of skin key to solution of skinspots) Fruitteelt 87(1997)22:12-13 Voorspellingssysteem schilvlekjes beschikbaar. (Prediction system for skinspots available) Fruitteelt 87(1997)33:16 taelofs, F.P.M.M. and H. Kemp. Santana (CPRO-9): een resistente bewaarbare kwaliteitsappel. (Santana (CPRO-0: a scab resistant storable quality apple) Fruitteelt 87(1997)17:20-21.
Schenk A.M.E. Gangbaar MBT lijkt bij gelijke prijzen het beste. (Accepted MBT the best with equal prices) Fruitteelt 87(1997)36:14-15
Schenk A.M.E. and H. Veijer Betere stikstofvoorzienin g in biologische fruitteelt door ondergroei.fßette/" nitrogen supply in integrated fruit growing) Fruitteelt 87(1997)32:14-15
Schouten, H.J. and A.M.E. Schenk Resistentie tegen appelschurft op sommige plaatsen doorbroken. (Resistance against apple scab has run in some places) Fruitteelt 87(1997)31:14-15
"romp,J . Maturity of apple cv. Elstar as affected by temperature during six-week period
103 A.R. 1997 Fruit Research Station
following bloom. Journal of Horticultural Science 72(1997)5:811-819
Ventura, M. and A. De Jager - Determinazione "non- distruttiva" dei solii solubili mediante riflettanza "NIR": esperien- ze sulle mele. (Non-destructive determination of sugars by the NIR-methodj Rivista di Frutticoltura e di ortofloricoltura 59(1997)12:67-70
Wagenmakers, P.S. - Grote Elstar verwacht in 1997. (Big E/star expected in 1997) FruitteeH 87(1997)34:22-23 - Hoge bomen: hou ze smal. (High trees: keep them slender) Fruitteelt 87(1997)50:10 11 - Licht bestimmt Ertrag und Qualität. Apfelanlage. (Light influences behaviour anc quality. Apple plantings). Obst und Garten 116(1997)12:444-445
Wertheim, S.J. - FPO-onderzoek aan kersenonderstammen. Weiroot 10 en 13 voldoen beter dan Colt (FPO-research on cherry rootstocks Weiroot 10 and 13 satisfy better than Colt) Fruit teelt 87(1997)7:20-21. - Landelijke FPO-onderstammenproef. P.16, P.22 en B.491 voldoen aan gestelde eisen. (National FPO rootstock trial. P.16, P.22 and B.491 meet requirements) Fruitteel 87(1997)19:14-15,17. - FPO-onderzoek aan kersenonderstammen. Gisela 5, een goede kersenonderstam. (FPL research on cherry rootstocks. Gisela 5, a good cherry rootstock) Fruitteel 87(1997)33:17-19. - Chemical thinning of deciduous fruit crops. Acta Horticulturae 463(1997):445-462. - Hazelnut cultivars suitable for Northwest European conditions. Fruit Varieties Journal 51(1997)2:88-93. - The hazelnut in Northwestern Europe: past, present and prospects. Nucis Newsletter 6(1997):17-19. - Walnut cultivar evaluation in The Netherlands. Acta Horticulturae 442(1997):425-427
Wertheim, S.J. and J.H. Bootsma - FPO-onderzoek naar chemische dunning van Conference. Meer onderzoek nodii voorgedegen advies. (FPO research on Conference pear thinning. More researct needed for sound advice) Fruitteelt 87(1997)16:24-25,27.
Wertheim,S.J. and de Groene, J.M. - Gisela 5 is goed te vermeerderen. (Gisela 5 propagates welf) Fruittee 87(1997)46:14.
Wijk, L. van, H. Balkhoven and C. Zuidam - Nieuwe formulering vbc werkt op gewone dopluis. (New formula vbc effective o brown scale) Fruitteelt 87(1997)50:20-21.
104 A.R. 1997 Fruit Research Station i/Voets, J. - Genoeg middelen voor bestrijding dopluis. (Sufficient chemicals for brown scale control) Groenten en Fruit, vakdeel Fruit 7(1997)7:7-8 Schadelijke wantsen op appel. (Noxious bugs on apple) Groenten en Fruit, vakdeel Fruit 7(1997)9:6-8
/Voets, J. and M.M. Giezen Gangbare wantsenmiddelen voldoen zoals verwacht. (Common bug control chemicals work as expected against the mullein bug) Fruitteelt 87(1997)4:19-20 Zwarte appelwant s deed schade verspreid over het land. (Black apple capsid damage throughout the country) Fruitteelt 87(1997)9:22-23 Schade door toortswants moeilijk te voorspellen. (Damage by mullein bug is difficult to forcast) Fruitteelt 87(1997)12:20-21 rVoets, J. and H. Stigter Perescheutwesp doet denken aan bacterievuur. (Sawfly on pear shoots reminds of fire blight} Groenten en fruit, vakdeel Fruit 7(1997)25:4 Wegnemen scheuten remt verspreiding perescheutwesp (Pruning the shoots hampers distribution of the sawfly on pear shoots). De Boomkwekerij 10(1997)29/30:25
/Voets, J. and H. Veijer Pissebedden zoeken het ook hogerop (Sawbugs try it higher in the tree). Groenten en Fruit, vakdeel Fruit 7(1997)37:12-13
/Vustenberghs.H., L. Beddegenoots and H. Kemp Zoektocht naar nieuwe kersen werpt vruchten af. (Search for new cherries proves fruitful). De Boomkwekerij 10(1997)49:18-21. Kersen voor het jaar 2000 (1). Vijf rassen voor het basissortiment. (Cherries for 2000 (1). Five cu/tivars for the core assortment). Fruitteelt 87( 1997)43:10-12. Kersen voor het jaar 2000 (2). Interessante nieuwigheden verder getoetst. (Cherries for 2000 (2). Interesting novelties further evaluated). Fruitteelt 87(1997)44:12-13.
hu, L.H., O. Borsboom and J. Tromp The effect of temperature on flower-bud formation in apple including some morpholo gical aspects. Scientia Horticulturae 70(1997):1-8
105 A.R. 1997 Fruit Research Station
Bulletins and publications on fruit growing nr.6 Hazelnut growing (Dutch), 84 pp, 2nd ed., April 1988 f 16.50 nr.7 From cold stores towards ULO-storage, (Dutch), 72 pp, March 1991 f 14.00 nr.8 Blueberry, cranberry and lingonberry culture (Dutch), 72 pp, March 1991 f 11.50 nr.22 S.J. Wertheim (ed.): De Peer (Dutch), 344 pp, November 1990 f 75.00 nr.23 P.D. Goddrie: Index of top fruit cultivars: 25 years' research in brief, 1970-1995 (Dutch, English, German), 147 pp, december 1995 f 27.5C nr.24 M.J. Groot (et.al): Quantitative Information Fruit Growing 1996/1997 (Dutch), 181 pp, December 1996 f 80.0C nr.25 S.J. Wertheim: Rootstock Guide (English), 144 pp, December 1998 f 80.0C
Annual Reports till 1992 f 15.0C Annual Reports after 1992 f 27.5C
To order any of the titles listed above, transfer the appropiate amount (prices include postage by surface mail) to the account of Fruitteeltpraktijkonderzoek (FPO) at Rand wijk, account with Rabobank Midden-Betuwe at Zetten, nr. 133968960) or by interna tional postal money order in Dutch currency, payable to the Fruitteeltpraktijkonderzoel at Randwijk, The Netherlands. Please indicate clearly the items being ordered.
106 A.R. 1997 Fruit Research Station
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"hose who are interested in the work of the Fruit Resaerch Station and wish to keep an ictive touch with and support its research are invited to become a donor member. In eturn you receive annually an information package (see below). You can make a choice )f the following items.
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op Fruit (TF) annual Report, excursion guides top fruit, PO-Newsletter' O ƒ 60,= O ƒ 100,= O ƒ 100, = mall fruit (SF) jinual Report, excursion guides small fruit, PO-Newsletter' 0/60,= 0/100,= 0/100,= op and Small Fruit innual Report, excursion guides top and small 'uit, FPO-Newsletter' 0/85,= 0/125,= 0/125,=
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