Research Article Received: 29 October 2012 Revised: 12 March 2013 Accepted article published: 30 March 2013 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/ps.3543 Two pear accessions evaluated for susceptibility to pear psylla Cacopsylla bidens ( ˇ Sulc) in Israel † Liora Shaltiel-Harpaz, a* Victoria Soroker, b Rika Kedoshim, a Roy Hason, a Tamar Sokalsky, a Kamel Hatib, c Irit Bar-Ya’akov c and Doron Holland c Abstract BACKGROUND: The pear psylla, Cacopsylla bidens ( ˇ Sulc), is one of the most damaging pests of commercial pear orchards in Israel. Psylla control is a major obstacle to efficient integrated pest management, necessitating research on cultivars with natural resistance to pear psylla. Recently, two pear accessions (Py.760-261 and Py.701-202) from the local Newe Ya’ar fruit tree live collection were identified as having apparent resistance to pear psylla. Our goal was to evaluate the resistance of these two accessions relative to the commercial cultivar Spadona Estiva, and to identify whether the resistance mechanisms in the former interfere with insect colonisation of the plant (antixenosis) or inhibit insect growth, development, reproduction and survival (antibiosis). RESULTS: Settlement and development of C. bidens was evaluated under natural conditions (pear orchard), semi-natural conditions (potted plants), and on detached branches and leaves (laboratory). Our results indicate that the selection Py.760-261 is 10 times more resistant than Spadona while Py.701-202 is five times more resistant. CONCLUSIONS: The resistance mechanism in both accessions appears to be antibiosis affecting nymph survival. These resistant accessions may be used as rootstock or as a source of resistant genes in breeding programmes. c  2013 Society of Chemical Industry Keywords: pear psylla; Cacopsylla bidens; resistant accessions; antibiosis; oviposition 1 INTRODUCTION The psyllids (Hemiptera: Psyllidae) are monophagous phloem- feeding insects. 1 – 3 Seven species of pear-feeding psyllids are present in North America, Europe, and other temperate and subtropical regions 4 of which most notably Cacopsylla pyricola F¨ orster, C. pyri L. and C. bidens ( ˇ Sulc) are pests of commercial pears. High-density populations of these insects can cause premature leaf and fruit drop, diminish plant growth, and reduce fruit size. In addition, their honeydew promotes sooty mould on leaves and russetting on fruits. 5 Pear psylla are also considered vectors of pear pathogens such as the bacterium Erwinia amylovora Burrill, which causes fire blight, 6 – 8 and Candidatus Phytoplasma pyri, causing pear decline disease. 9 C. pyricola is the vector in northern America 10 and C. pyri in Europe 11 Since the pear psylla rapidly acquires inherited resistance to pesticides, 12 the range of efficient chemicals for its control is narrowing down and the applied concentrations are constantly increasing, while consumers demand lower pesticide application in the orchards. Indeed, psylla control is one of the major obstacles to efficient integrated pest management (IPM) in pear orchards, 13 providing the impetus for research on cultivars with natural resistance to pear psylla, with potential for use as a genetic source for breeding projects or as a source of natural deterrents. Substantial research has been done on pear cultivars resistant to the two most common pear psyllids in Europe and northern America: C. pyri and C. pyricola. 14 – 18 However, hardly any work has been done on pear cultivars resistant to C. bidens. This species is the common pear psylla in Israel, and was also reported in Lebanon, Moldova, Romania, France, and Italy but is not considered a pest in western Europe. 19 In the climatic conditions of the Middle East C. bidens can establish nine generations per year, and it probably does not undergo real reproductive diapause but rather temperature-mediated quiescence (Soroker et al., unpublished). Resistance to pear psylla (Cacopsylla species) has been found mainly in Asian pear species Pyrus betulifolia Bunge, P. calleryana Decne., P. fauriei Schneid., P. ussuriensis Maxim. and ∗ Correspondence to: Liora Shaltiel Harpaz, Migal Galilee Research institute, P.O. Box 831, Kiryat Shmona 11016, Israel. E-mail: lioraamit@bezeqint.net † This paper is the first in a series of studies examining resistance of pear varieties to pear psylla. a Migal Galilee Research institute, P.O. Box 831, Kiryat Shmona 11016, Israel b Department of Entomology, Agricultural Research Organization, The Volcani Center, P.O.Box 6, Bet Dagan 50250, Israel c Unit of Deciduous Fruit Tree Sciences, Newe Ya’ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel Pest Manag Sci (2013) www.soci.org c  2013 Society of Chemical Industry