North-Western Journal of Zoology Vol. 6, No. 1, 2010, pp.54-62 P-ISSN: 1584-9074, E-ISSN: 1843-5629 Article No.: 061106

Measuring population density ( pyri L. and C. pyricola Förster): review of previous methods and evaluation of a new technique

Gábor JENSER1, Éva SZITA1* and János BÁLINT2

1. Plant Protection Institute of Hungarian Academy of Sciences, P.O. Box 102 H-1525 Budapest Hungary. 2. Department of Horticulture, Sapientia University, Faculty of Technical and Human Sciences, 1/c Shigisoarei st. Tirgu-Mures, Romania. * Corresponding author: É. Szita, Plant Protection Institute of Hungarian Academy of Sciences, P.O. Box 102 H-1525 Budapest Hungary, E-mail: [email protected]

Abstract. Following the survey of the proposed and applied methods the wash-down procedure has been evaluated to collect the pear psylla larvae (Cacopsylla pyri Linnaeus and C. pyricola Förster) in order to establish their population density. To select the larvae the shoots or flowers should be washed-down by water containing 1% detergent. To concentrate larvae, the detergent solution was strained through filter paper. After that it is possible to count exactly the number of larvae by using dissection microscope. By this way the total number of the developing larvae occurring in the flowers or on the shoots could be established. By the application of this method, it is possible to obtain real data about the absolute population density and its changes, as well as the susceptibility or tolerance of the pear cultivars to pear psylla. The data provided by the wash-down method was compared with the traditional limb beating method.

Keywords: methodology, wash-down method, absolute density estimation, Cacopsylla pyri, Cacopsylla pyricola

Introduction the most dangerous species in North America (Alston & Murray 2007, Horton 1994, Horton et High psylla population densities in pear orch- al. 1992) and in Great Britain (Hodgson & ards have been reported over many decades in Mustafa 1984, Solomon et al. 1989). Mixed Europe, with the first outbreaks occurring in populations of these species were reported the early 1950s in France (Bonnemaison & from The Netherlands (Trapman & Blommers Missonnier 1955, 1956). Psylla infestation is the 1992, Van der Blom et al. 1985). These two most important pest management problem of species are almost equal in size and have pear-growing districts in Europe (Geoffrion similar life strategies. The reasons of its high 1984, Gobin et al. 2005, Jenser 1988, Pasqualini population density and the possibilities of the et al. 2003, Erler 2004b). prevention of damage are studied since that Two Psylla species have caused severe time. The development of control strategies, economic damage in pear orchards since the effects of insecticides, causes of insecticide beginning of commercial pear production. resistance, role of the predators in population While Cacopsylla pyri (Linneaus, 1758) is the dynamics, and the effect of phytotechnique main pest in most of Europe (Berrada et al. (Atger & Lemoine 1984, Brunner 1984, Pfeiffer 1996, Civolani & Pasqualini 2003, Erler et al. & Burts 1983, Westigard et al. 1980) were 2007, Jenser 1988), C. pyricola (Förster, 1848) is investigated continuously, and the individual

©NwjZ, Oradea, Romania, 2010 North-West J Zool, 6, 2010 www.herp-or.uv.ro/nwjz Oradea, Romania Pear psylla collecting methods 55 number or the changes of the population den- during a relatively short time. These can be sities have been established by the different distinguished from methodological point of methods. view by the dimension of collecting tools, This paper presents a review of the which can be two- and three-dimensional. methods used for collecting pear psyllids. A Two-dimensional methods: beating tray methods. description of the wash-down method is The two-dimensional collecting tool is a textile presented, along with a comparison with the sheet stretched on a rectangular or round traditional limb-beating method. frame, called beating tray or frappage. The

white textile-covered tray is held beneath a tree Review of the methods for determining pear limb, and the limb is hit three times with a psylla population density (Cacopsylla pyri and rubber hose. Dislodged psylla and other ani- C. pyricola) mals which fell on the tray are counted or Yellow sticky-board trap for pear psylla detection collected by aspirator immediately in the was developed by Kaloostian and Yeomans in orchard. 1944 (Kaloostian 1961). This method was Authors used beating trays in large variety examined and estimated by several authors of size and shape. Burts and Retan (1973) (Adams & Los 1989, Horton 1993, Kaloostian developed the most widespread beating tray 1961, Krysan & Horton 1991, Brown et al. type which is 45 x 45 cm (18 x 18 inch; area ~ 2009). Significant differences were established 0.2 m2) in size. This procedure was applied by by Adams and Los (1989) regarding the several authors (Burts & Brunner 1981, Daniel effectiveness of yellow sticky traps placed at & Wyss 2004, Deronzier 1984, Erler 2004b, different heights, orientations and quadrants of Horton 1994, 1993, 1994, Horton et al. 1992, pear trees. Hue and intensity of reflection 2008, Krysan & Horton 1991, Paulson & Akre appear to be important for eliciting positive 1992, Pfeiffer & Burts 1983, Stratopoulou & reflection response by pear psylla adults to Kapatos 1995, Westigard & Moffitt 1984). visual traps. The greatest captures occurred for Alston and co-workers (Alston & Murray 2007, hues with reflection peaks in the 520 to 600-nm Alston & Reding 1998, 2003) published a pesti- range of the spectrum (Adams et al. 1983). cide program against pear psylla for farming Seasonality of the catch and flight activity of practice: 0.2 adult psylla/tray was suggested as pear psylla (C. pyricola) was observed by treatment threshold under monitoring of psylla several authors (Civolani & Pasqualini 2003, population with Burts and Retan’s (1973) Erler 2004b, Horton 1994, Krysan & Horton beating tray method. Beating tray with 0.25 m2 1991), and diurnal difference was reported by area was used by several authors as well (Horton 1993). Intraorchard changes in distri- (Deronzier 1984, Rieux & D'Arcier 1983, Rieux bution associated with leaf fall were investi- et al. 1992, Trapman & Blommers 1992). Herard gated by Horton et al. (1993). Reduced catch (1985, 1986), Herard and Chen (1985), Miliczky can be observed under cool weather conditions (2005) and Brown et al. (2009) applied 0.5 m2 (Horton 1994). tray in their surveys. Some researchers used beating trays with unique size: Civolani and Limb beating or limb jarring to collect Pasqualini (2003) used 55 cm x 25 cm (area ~ specimens from trees and shrubs has been 0.14 m2) frappage in Italy, Severin and co- known for a long time and in several varia- workers (1984) applied 40 cm x 40 cm (area tions. It is possible to take a high number of 0.16 m2) sized one in France, while Santas samples and to establish the density of psylla (1987) in Greece worked with 1 m x 1 m (area 1 adults and other with these methods m2) sized beating tray. The authenticity of the

North-West J Zool, 6, 2010 56 Jenser, G. et al. data provided by this type of method depends (1995), Jenser et al. (2009) and the second considerably on weather condition. When author of the present paper. temperature increases, most of the adults Both the application of the sticky board away (Deronzier & Atger 1980). Therefore it is traps and beating tray provide accurate infor- necessary to take the sample in the morning mation about the changes of pear psylla popu- (Deronzier & Atger 1980, Erler 2004b, Horton lation density. A few of the authors provide 1994). information on the correlation of catch data of different collecting methods. Adams and Los Three-dimensional methods: beating umbrella (1989) concluded that Lightning Yellow and methods. Using three-dimensional limb beating Arc Yellow sticky traps were more highly and methods the dislodged insects fall into a more consistently correlated with the occur- funnel-like structure instead of a flat sheet. rence of pear psylla eggs and nymphs on pear This funnel-like structure is often called spurs and sooty mold blemishing on fruit than “beating umbrella”. Due to its vertical exten- were counts obtained by beating tray. In the sion, this method is much less temperature- investigations of Krysan and Horton (1991) and wind-sensitive and much more suitable for correlations between trap catches and beating collecting fast moving or flying beneficial tray numbers tended to be non-significant, organisms (e.g. spiders, pirate bugs) than the while Horton (1994) found it to be significant. two-dimensional methods mentioned above. The amount of collected insects generally The psylla eggs were counted on the shoots and makes necessary the laboratory process. leaves using a binocular dissecting microscope Steiner (1962) investigated the arthropod by Jenser (1988), Adams and Los (1989), populations occurring in the orchards, used a Stratopoulou and Kapatos (1995), Erler (2004c), plastic funnel with an aperture of 0.25 m2 Erler and Cetin (2005, 2007) and Erler et al. instead of textile umbrella. A glass vessel of (2007). A few of the authors investigated and 335 cm3 was used for gathering the specimens counted both the eggs and larvae (Brunner at the bottom of the funnel. Fauvel et al. (1981) 1984, Pasqualini et al. 2003, Scutareanu et al. used the same technique, they filled the 1999, Mari et al. 2009). Counting the eggs and gathering vessel with a small amount of 70% larvae on the shoots provides real data, but the alcohol. Rieaux (1999) mentioned this method sample must be taken into the laboratory and it above as “Fauvel’s funnel method”. Bouyjou et is necessary to complete the counting within a al. (1984) used this technique for predator and short time. At the same time this procedure is prey population density estimation in pear rather time-consuming. orchards. Solomon et al. (1989) applied a gauze The corrugated cardboards could provide as funnel of 0.3 m2 area and brushed down the overwintering places for both the specimens of dislodged insects into a collecting jar. Winkler- pear psyllids and predators (Bogya 1995, type umbrella is a textile funnel 70 cm in Bogya et al. 1999, Civolani & Pasqualini 2003, diameter combined with a textile tube at its Horton et al. 2002, Jenser 1988). The corrugated bottom. The bottom of the textile tube can be cardboards of equal size should be placed at closed with a piece of string. Dislodged least on the trunk of 25 trees of the same can be collected directly into the textile cultivar. The corrugated cardboards must be tube (ca. 15 cm in diameter) and then put into a removed after the end of the falling of the plastic bag until preparation. The tube can also leaves, when the air-temperature is permanent- be combined with a colleting jar tied on it. ly under 0 °C. Before counting the collected Winkler-type umbrella (without collecting jar) adults must be killed or refrigerated. The num- was used by Bogya et al. (1999), Markó et al.

North-West J Zool, 6, 2010 Pear psylla collecting methods 57 ber of the adults collected by the corrugated litter samples. They work on the principle that cardboard might provide relatively appropri- insects and other that normally live ate information about the density of the over- in soil and litter will respond negatively to wintering population (Jenser 1988). By using light and heat. Therefore, a light source is used this information it is possible to determine the to force the arthropods to move downward, intensity of the application of the insecticides where they will fall into a funnel and then into in springtime. Our and V. Markó (pers. comm.) a container of ethanol. The Berlese funnel was experiments revealed that during the vegeta- used by Stäubli and co-workers (1992) to tional season only a few psylla larvae can be extract the larvae of C. pyri with good results. found in the cardboards. Salticid and philodro- Trapman and Blommers (1992) gathered 25 mid spiders from the canopy and the herba- growing twigs per row for processing this ceous layer of the orchards had sheltered for method in order to estimate the densities of moulting and egg laying occasionally. Lace- juvenile pear suckers and pirate bugs. wings (Neuroptera) also used the cardboards Organdy bags were used to provide rough for transforming into a pupa. estimates of absolute pear psylla densities The mite brushing machine or leaf brushing (Horton 1994, Horton et al. 1993). Large machine developed by Henderson and organdy bags (ca. 1 m long, 0.25 m in diameter) McBurney (1943) is a technology that can open at one end were carefully dropped over reduce the time required to obtain either pear shoots. Bags were closed around the absolute counts or estimates of arthropods on shoots, and the shoots were clipped off at the leaves from samples. Macmillan (2005) gives a base of the bag. Samples were taken into the detailed description of this method: “All mite laboratory and psylla specimens were counted. brushing machines operate on the same This method is temperature sensitive, and principle. Two rollers with overlapping soft collections were made in the morning when bristles counter-rotate. Plant leaves are passed psylla adults were inactive. between the rollers and the direction of rotation of the rollers sweeps the surface of the Description of a new technique: leaf in a downward direction, knocking the wash-down method material free from the leaf surface, including Only few antecedents of the wash-down arthropods”. For further information in method can be found to different application and evaluation of this useful tool groups in the literature, but not for any psyllid see Macmillan (2005). The mite brushing species. Jones and Prendergast (1937) worked machine is suitable for removing psylla larvae out a method of obtaining a density index of from their first-instar stage. The population citrus red mite, and it was also applied for densities of psylla larvae were estimated with predatory mites and thrips (Boller 1984, Hill & this method by Westigard and Moffitt (1984), Schlamp 1984). For the examination four times Burts (1988) and Paulson and Akre (1992). ten bunches/ 4 x 10 of flowers, sprouts or Investigating leaves of growing shoots (the shoots (10 cm long) should be sampled. Since proximal leaf, the distal leaf and three leaves pear psylla species prefer to lay eggs on young, from the middle), Burts (1988) reported that 0.3 succulent foliage, significant differences occur larvae per leaf had produced detectable fruit in the density of the eggs and larvae on the russet. green shoots and on the shoots with terminal Berlese funnel is a widespread technique for bud (Basky 1978, Brunner 1984, Burts 1984, Fye extracting arthropods mainly from soil and 1982). According to our examinations inside

North-West J Zool, 6, 2010 58 Jenser, G. et al. the crown of the same trees, 80% of the eggs sampling because of the physical disturbance of other were laid on the growing shoots (Jenser 1988). limbs of a given tree. The sampling period of the wash- down method has begun two weeks later and finished Therefore, it is a basic requirement to take into earlier than that of the limb-beating method. consideration the conditions of the sampled The correlation between mean densities of wash- shoots. On the other hand, the samples con- down and limb beating protocol samples was evaluated taining both green shoots and terminals pro- by linear regression using Statistica 6 (2003) software. vide misleading results. In spring bunches of flowers, following that, in late spring and summer the green shoots (spurs), and in late Results and Discussion summer the terminals should be collected only. The sampled flowers, green shoots and termi- Mean densities of psylla larvae caught by nals are put into tightly closed plastic bag and wash-down method and mean densities of so it is safely transferred to the laboratory. The psylla adults captured by limb beating showed samples have to be stored in a refrigerator at 4 large variation in number during the 2 years – 5 °C until the processing. In order to select (Fig. 1). An extreme peak of psylla captures the larvae, the flowers, green shoots or occurred in the first part of May 2007 despite of terminals are dipped in water containing 1% of the application of the abamectin (Fig. 1B). The detergent, where they are soaked for 3 – 4 possible reason of the inefficiency in abamectin minutes. Afterwards, they should be shaken could be that the extremely cold weather (-2 strongly for 2 – 3 minutes to separate pear °C; www.met.hu) might have inhibited its psylla larvae from the surface of flowers, effect. The sampling data of this date were leaves and sprouts. Since a part of the larvae regarded as outlier, and therefore were exclud- leave the sample material, it is necessary to ed from the correlation analysis. Although wash out the plastic bag, and this water should highly variable, wash-down method captures be added to the water in the pot. To con- showed positive significant correlation to limb centrate the larvae, the water has to be strained beating counts in each sampling year (Fig. 2). through a filter-paper placed in a funnel. By The linear regression analysis of the captures this way all the larvae occurring on the for these two methods showed robust fit (Fig. 2 2 flowers, leaves and sprouts concentrate on the 2: r = 0.7598 in 2006; r = 0.9153 in 2007). filter-paper. By the application of this method Different types of limb-beating protocols we can establish the exact quantity of the proved to be efficient tools of relative popu- psylla larvae. lation density monitoring (Bogya et al. 1999, Civolani & Pasqualini 2003, Erler 2004b, Horton et al. 1992, Markó et al. 1995, Solomon Material and methods et al. 1989, Trapman & Blommers 1992). Pest management programs routinely compare the The pear orchard in the study was located in objective having develop an effective pest Legyesbénye, in the northern part of Hungary. The orchard is 20 ha in size and an IPM pesticide program monitoring system. Horton (1994) compared was applied (polysulfide, Vaseline® oil, abamectin, beating tray data (Burts & Retan 1973) to the diflubenzron). The investigations were carried out on data of an absolute density estimation method pear variety ‘Williams’ in the growing seasons of 2006 (Organdy bag method, detailed previously), and 2007 on 6- to 7-year-old trees. The psylla samples and his results suggested that beat trays could were taken biweekly. Two collecting methods were applied: the new wash-down method and limb-beating be used to estimate absolute densities. The by Winkler-type umbrella. 20 branches were sampled in wash-down method ab ovo results absolute 5 repetition in every sampling date by Winkler-type density estimation. The linear regression of the umbrella. Only one branch per tree was beaten at a given

North-West J Zool, 6, 2010 Pear psylla collecting methods 59

Figure 1. Pear psylla mean densities in 2006 (A) and 2007 (B) in Legyesbénye, Hungary. The Y axis is divided into 3 parts with different scale units due to the large variation in catches. Grey line with grey squares = psylla larvae captured by wash-down method; black line with black squares = psylla adults captured by limb beating with Winkler-type umbrella.

wash down method and Winkler-type umb- on pear (and other tree orchard cultivars), rella method revealed that the latter method is where the majority of predators feed on im- also suitable to estimate absolute adult psylla mature stages on fruit pests. densities, similarly to Retan & Burts’s (1973) The major advantages of the wash-down beating tray method. This information can be method are the independence of the weather significant in the study of beneficial arthropods conditions (temperature, wind, rain) and the

North-West J Zool, 6, 2010 60 Jenser, G. et al.

Figure 2. Scatter plots and linear regressions relating mean catches of wash-down to limb beating in 2006 (A) and in 2007 (B).

daily rhythm of the examined psylla stages. Connecticut. Journal of Economic Entomology 82: 1448- Since practically every larvae developing on 1454. Alston, D.G., Murray, M. (2007): Pear Psylla. Utah State the flowers and shoots are extracted, the wash- University Extension, Extension Entomology Ent-62-07: down method provides suitable data about the 1-4. pear psylla population density and its changes, Alston, D.G., Reding, M.E. (1998): Pear Psylla. Utah State University Extension, Extension Entomology 98/1: 1-4. as well as about the effectiveness of the insecti- Alston, D.G., Reding, M.E. (2003): Pear Psylla. Utah State cides. This method could also provide signi- University Extension, Extension Entomology: 1-6. ficant data to judge the susceptibility or tole- Atger, P., Lemoine, J. (1984): Observations sur l’incidence de la variete et du mode de conduitedu poirier sur la rance of the pear cultivars to pear psylla spe- pullulation des psylles. IOBC/WPRS Bulletin 7: 241-244. cies. Berrada, S., Nguyen, T.X., Fournier, D. (1996): Comparative toxicities of some insecticides to Cacopsylla pyri L. (Hom., ) and one of its important biological control agents, F. (Het., Anthocoridae). Journal of Applied Entomology 120: 181-185. Acknowledgements. We would like to thank Judit Vajkóné Bogya, S. (1995): Kalitpókok (Clubionidae), mint a biológiai Tarjáni, Mihály Lampert and the directors of Pisák Ltd. for védekezés perspektivikus eszközei almagyümölcsösben. their kind help and collaboration during our surveys. Növényvédelem 31: 149-153. [in Hungarian] Financial support was held by the NKFP (Nr. 4/012/04). Bogya, S., Szinetár, C., Markó, V. (1999): Species composition of spider (Araneae) assemblages in apple and pear orchards in the Carpathian Basin. Acta Phytopathologica et Entomologica Hungarica 34: 99-121. Bonnemaison, L., Missonnier, J. (1955): Recherches sur le References déterminisme des formes estivales ou hivernales et de la diapause chez le Psylle du poirier (Psylla pyri L.). Adams, R.G., Domeisen, C.H., Ford, L.J. (1983): Visual trap Annales des Épiphyties ser. C 6: 457- 528. for monitoring pear psylla (Homoptera: Psyllidae) adults Bonnemaison, L., Missonnier, J. (1956): Le Psylle du poirier on . Environmental Entomology 12: 1327-1331. (Psylla pyri L.) morphologie et biologie méthodes de Adams, R.G., Los, L.M. (1989): Use of sticky traps and limb lutte. Annales des Épiphyties 2: 263-331. jarring to aid in management decisions for summer Bouyjou, B., Canard, M., Nguyen, T.X. (1984): Analyse par populations of the pear psylla (Homoptera: Psyllidae) in battage des principaux predateurs et proires potentielles

North-West J Zool, 6, 2010 Pear psylla collecting methods 61

en verger de poiriers non traite. IOBC/WPRS Bulletin 7: toille. Etude de l'influence de quelques facteurs sur 148-166. l'efficacite du battage. Agronomie 1: 105-113. Brown, R.L., Landolt, P.J., Horton, D.R., Zack, R.S. (2009): Geoffrion, R. (1984): Les psylles du Poirier - historique, Attraction of Cacopsylla pyricola (: Psyllidae) to importance economique. IOBC/WPRS Bulletin 7: 13-15. female psylla in pear orchards. Environmental Gobin, B., Bylemans, D., Peusens, G. (2005): Biological efficacy Entomology 38: 815-822. of kaolin against pear sucker Psylla pyri in winter and Brunner, J.F. (1984): The development, distribution and summer applications. IOBC/WPRS Bulletin 28: 193-197. sampling for the pear psyllids, Psylla pyricola. Henderson, C.F., McBurney, H.Y. (1943): Sampling technique IOBC/WPRS Bulletin 7: 81-96. for determining populations of the citrus red mite and its Burts, E.C. (1988): Damage threshold for pear psylla nymphs predators. USDA Circ. 671. (Homoptera: Psyllidae). Journal of Economic Herard, F. (1985): Analysis of parasite and predator Entomology 81: 599-601. populations observed in pear orchards infested by Psylla Burts, E.C., Brunner, J.F. (1981): Dispersion statistics and pyri (L.) (Hom.: Psyllidae) in France. Agronomie 5: 773- sequential sampling plan for adult pear psylla. Journal of 778. Economic Entomology 74: 291-294. Herard, F. (1986): Annotated list of the entomophagous Burts, E.C., Retan, A.H. (1973): Detection of pear psylla. complex with pear psylla, Psylla pyri (L.) (Hom.: Washington State University Cooperative Extension Psyllidae) in France. Agronomie 6: 1-34. Service, Mimeo 3069. Herard, F., Chen, K. (1985): Ecology of Anthocoris nemorum Civolani, S., Pasqualini, E. (2003): Cacopsylla pyri L. (Hom., (L.) (Het.: Anthocoridae) and evaluation of its potential Psyllidae) and its predators relationship in Italy's Emilia- effectiveness for biological control of pear psylla. Romagna region. Journal of Applied Entomology 127: Agronomie 5: 855-863. 214-220. Hodgson, C. J., Mustafa, T. M. (1984): Aspects of chemical and Daniel, C., Wyss, E. (2004): Efficacy of different insecticides biological control of Psylla pyricola Foerster in England. and a repellent against the European pear sucker IOBC/WPRS Bulletin 7: 330-353. (Cacopsylla pyri). Pp. 1-5. 11th International Conference Horton, D. R. (1993): Diurnal patterns in yellow trap catch of on Cultivation Technique and Phytopathological pear psylla (Homoptera: Psyllidae): differences between Problems in Organic Fruit-Growing. sexes and morphotypes. Canadian Entomology 125: 761- Deronzier, S. (1984): Dynamique des populations de Psylla 767. pyri L. en verger abandonné, dans le sud-est de France. Horton, D.R. (1994): Relationship among sampling methods Agronomie 4: 549-556. in density estimates of pear psylla (Homoptera: Deronzier, S., Atger, P. (1980): Éléments d’étude de la Psyllidae): implications of sex, reproductive maturity, dynemique des populations de Psylla pyri L. dans la and sampling location. Ecology and Population Biology Basse Vallée du Rhône: périod hivernale et printanière. 87: 583-591. Acta Oecologica 1: 247-258. Horton, D.R., Burst, E.C., Unruh, T.R., Krysan, J.L., Coop, Erler, F. (2004a): Laboratory evaluation of a botanical natural L.B., Croft, B.A. (1993): Intraorchard changes in product (AkseBio2) against the pear psylla Cacopsylla distribution of winterform pear psylla (Homoptera: pyri. Phytoparasitica 32: 351-356. Psyllidae) associated with leaf fall in pear. Annals of the Erler, F. (2004b): Natural enemies of the pear psylla Cacopsylla Entomological Society of America 86: 599-608. pyri in treated vs untreated pear orchards in Antalya, Horton, D.R., Debra, A.B., Hinojosa, T., Lewis, T.M., Miliczky, Turkey. Phytoparasitica 32: 295-304. E.R., Lewis, R.R. (2002): Diversity and phenology of Erler, F. (2004c): Oviposition deterrency and deterrent predatory arthropods overwintering in cardboard bands stability of some oily substances against the pear psylla placed in pear and apple orchards of central Washington Cacopsylla pyri. Phytoparasitica 32: 479-485. state. Annals of the Entomological Society of America 95: Erler, F., Cetin, H. (2005): Evaluation of some selective 469-480. insecticides and their combinations with summer oil for Horton, D.R., Guédot, C., Landolt, P.J. (2008): Attraction of the control of the pear psylla Cacopsylla pyri. male summerform pear psylla to volatiles from female Phytoparasitica 33: 169-176. pear psylla: effects of female age, mating status, and Erler, F., Cetin, H. (2007): Effect of Kaolin particle film presence of host plant. The Canadian Entomologist 140: treatment on winterform oviposition of the pear psylla 184-191. Cacopsylla pyri. Phytoparasitica 35: 466-473. Horton, D.R., Higbee, B.S., Krysan, J.L. (1994): Postdiapause Erler, F., Yegen, O., Zeller, W. (2007): Field evaluation of a development and mating status of pear psylla botanical natural product against the pear psylla (Homoptera: Psyllidae) affected by pear and nonhost (Homoptera: Psyllidae). Journal of Economic species. Annals of the Entomological Society of America Entomology 100: 66-71. 87: 241-249. Fauvel, G., Rambier, A., Balduque-Martin, R. (1981): La Horton, D.R., Higbee, B.S., Unruh, T.R., Westigard, P.H. techique du battage por la surveillance des ravageurs en (1992): Spatial characteristics and effects of fall density cultures fritiére et florale. I. Comparaison des resultats and weather on overwintering loss of pear psylla obtenus en verger de pommiers avec des entonnoirs (Homoptera: Psyllidae). Environmental Entomology 21: rigides de taille moyenne et avec des entonnoirs de 1319-1332.

North-West J Zool, 6, 2010 62 Jenser, G. et al.

Jenser, G. (1988): A füstösszárnyú körtelevélbolha (Cacopsylla Santas, L. A. (1987): The predators' complex of pear-feeding pyri L.) tömeges elszaporodása. (On the mass appearance psyllids in unsprayed wild pear trees in Greece. of the pear psylla Cacopsylla pyri L). Növényvédelem 24: Entomophaga 32: 291-297. 107-111. [in Hungarian] Scutareanu, P., Lingeman, R., Drukker, B., Sabelis, M.W. Jenser, G., Süle, S., Szita, É.V.., Tarjáni, J. (2009): A (1999): Cross-correlation analysis of fluctuations of pear füstösszárnyú körte-levélbolha (Cacopsylla pyri Linnaeus) psyllids and anthocorid bugs. Ecological Entomology 24: elleni védekezés újabb követelményei és lehetségei. 354-362. Növényvédelem 45: 595-603. [in Hungarian] Severin, F., Bassino, J.P., Blanc, M., Bony, D., Gendrier, J.P., Kaloostian, G. H. (1961): Evaluation of adhesives for sticky Reboulet, J.N., Tisseur, M. (1984): Importance des board traps. Journal of Economic Entomology 54: 1009- heteropteres predateurs des psylles du poirier dans le 1011. Sud-Est de la France. IOBC/WPRS Bulletin 7: 140-145. Krysan, J.L., Horton, D.R. (1991): Seasonality of catch of pear Solomon, M.G., Granham, J.E., Easterbrook, M.A., Fitzgerald, psylla Cacopsylla pyricola (Homoptera: Psyllidae) on J.D. (1989): Control of the pear psyllid, Cacopsylla pyricola yellow traps. Environmental Entomology 20: 626-634. in South East England by predators and pesticides. Crop Macmillan, C.W. (2005): A protocol for using the mite Protection 8: 197-205. brushing machine for measuring densities of Willamette Stäubli, A., Hächler, M., Pasquer, D., Antonin, P., Mittaz, C. spider mites on grapes. California Polytechnic State (1992): Dix années d’experiences et d’observations sur ée University, San Luis Obispo. psylle commun du poirier. Revue Suisse Viticulture Mari, D., Ogurli, I., Prijovi, M., Peri, P. (2009): Arboriculture et Horticulture 24: 89-104. Effectiveness of Azadirachtin (NeemAzal-T/S) in StatSoft, Inc. (2003). STATISTICA (data analysis software controlling pear psylla (Cacopsylla pyri) and European system), version 6. www.statsoft.com. red mite (Panonychus ulmi). Pesticidi i fitomedicina 24: Steiner, H. (1962): Methoden zur Untersuchungen der 123-131. Populationsdynamik in Obstanlagen. Entomophaga 7: Markó, V., Merkl, O., Podlussány, A., Vig, K., Kutasi, C., 207-214. Bogya, S. (1995): Species composition of Coleoptera Stratopoulou, E.T., Kapatos, E.T. (1995): The dynamics of the assemblages in the canopies of Hungarian apple and adult population of pear psylla, Cacopsylla pyri L. (Hom., pear orchards. Acta Phytopathologica et Entomologica Psyllidae) in the region of Magnesia (Greece). Journal of Hungarica 30: 221-245. Applied Entomology 119: 97-101. Miliczky, E.R., Horton, D.R. (2005): Densities of beneficial Trapman, M., Blommers, L. (1992): An attempt to pear sucker arthropods within pear and apple orchards affected by management in the Netherlands. Journal of Applied distance from adjacent native habitat and association of Entomology 114: 38-51. natural enemies with extra-orchard host plants. Van der Blom, J., Drukker, B., Blommers, L. (1985): The Biological Control 33: 249-259. possible significance of various groups of predators in Pasqualini, E., Civolani, S., Corelli Grappadelli, L. (2003): preventing pear psylla outbreaks. Mededelingen van de Particle film technology: approach for a biorational Faculteit der Landbouwwetenschappen Rijksuniversiteit control of Cacopsylla pyri (Rhynchota: Psyllidae) in Gent 50: 419-424. Northern Italy. Bulletin of Insectology 55: 39-42. Westigard, P.H., Lombard, P.B., Allen, R.B., Strang, J.G. Paulson, G.S., Akre, R.D. (1992): Evaluating the effectiveness (1980): Pear psylla: Population suppression through host of as biological control agents of pear psylla plant modification using daminozide. Environmental (Homoptera: Psyllidae). Journal of Economic Entomology 9: 275-277. Entomology 85: 70-73. Westigard, P.H., Moffitt, H.R. (1984): Natural control of the Pfeiffer, D.G., Burts, E.C. (1983): Effect of tree fertilization on pear psylla (Homoptera: Psyllidae): Impact of mating numbers and development of pear psylla (Homoptera: disruption with the sex pheromone for control the Psyllidae) and on fruit damage. Environmental (Lepidoptera: Tortricidae). Journal of Entomology 12: 895-901. Economic Entomology 77: 1520-1523. Rieux, R., D'Arcier, F.F. (1983): Etude de la dynamique et de la Reparation spatiale des populations estivales de Psylla pyri L. et de quelques uns de ses predaturs en verger de poiriers. IOBC/WPRS Bulletin 7: 167-175. Rieux, R., Lyoussoufi, A., Armand, E., D'Arcier, F.F. (1992): Submitted: 01 November 2009 Dynamique des populations hivernales et post- / Accepted: 05 April 2010 hivernales du Psylle du poirier Psylla pyri (L.) (Homoptera: Psyllidae). Acta Phytopathologica et Published Online: 27 April 2010 Entomologica Hungarica 27: 545-549. Rieux, R., Simon, S., Defrance, H. (1999): Role of hedgerows and ground cover management on arthropod populations in pear orchards. Agriculture Ecosystems and Environment 73: 119-127.

North-West J Zool, 6, 2010