Pear psyllids (Cacopsylla spp., Hemiptera: Psyllidae) are major pests of European pear (Pyrus communis L.) in orchards in most temperate regions where the crop is grown (Berrada et al., 1995; Westigard et al., 1970). In North America, the only species present is Cacopsylla pyricola (Förster), whereas in Europe, Cacopsylla pyri (L.) and, in the more northern regions, Cacopsylla pyrisuga (Förster) are also major pest species. Both adults and nymphs feed primarily in the vascular tissue of the leaves, petioles, and succulent shoots. Prolonged feeding in the phloem by nymphs affects the plant directly by inducing necrosis and premature defoliation. The nymphs excrete excess sugar as honeydew, which can cause russeting of young fruit. Sooty mold fungus grows on the honeydew, resulting in reduced photosynthesis and marked fruit. The insect is also the vector of the pear decline phytoplasma (Hibino et al., 1971). Pear psylla have rapidly developed resistance to commonly used pesticides such as pyrethroids (Pree et al., 1990), azinphosmethyl, endosulfan, Perthane, and fenvalerate (Follet et al., 1985), and biological controls are not always sufficiently effective (Shaltiel and Coll, 2010).
Host resistance and pear psylla behavior have recently been reviewed by Bell and Puterka (2003) and Nin et al. (2012). The behavioral and physiological responses of arthropod pests to resistant host genotypes are termed modes of host plant resistance, as distinct from the underlying mechanisms of resistance. Major modes of host plant resistance are as follows: 1) antixenosis, which can be observed in terms of difficulty in orientation and reduced settling (i.e., host finding), adult and nymphal feeding, and oviposition; 2) antibiosis, which delays development, increases mortality, reduces fecundity, and reduces egg hatch; and 3) tolerance, or the ability to withstand infestation without damage. The combination of these effects determines the overall level of pest colonization and damage to the host plant.
Resistance within the genus Pyrus to pear psylla has been demonstrated in the East Asian pear species P. betulifolia Bunge, P. calleryana Decne., P. fauriei Schneid., P. ussuriensis Maxim., and P. ×bretschneideri Rehd., in P. ussuriensis × P. communis hybrids (Harris, 1973; Harris and Lamb, 1973; Pasqualini et al., 2006; Quamme, 1984), in P. pyrifolia (Burm.) Nakai × P. communis hybrids (Braniste et al., 1994; Robert et al., 2004, 2005), and in a few genotypes of the European “snow pear,” P. nivalis Jacq. (Quamme, 1984; Westigard et al., 1970). Cultivars within the European pear species, P. communis L. with moderate to high levels of resistance include the old Italian cultivars Spina Carpi (Quarta and Puggioni, 1985; Briolini et al., 1988), Doyenne du Poitiers, and D’Aoǔt Lamer (Robert et al., 2004, 2005), and 15 landrace cultivars from Eastern Europe (Bell, 1992, 2003; Bell and Stuart, 1990). Two wild pears of uncertain parentage were found in Israel to have reduced susceptibility to C. bidens (Šulc) (Shaltiel-Harpaz et al., 2014). A high level of nymphal feeding resistance has also been identified in ×Sorbopyrus auricularis (Knoop) C. K. Schneid. (Bell, 1992; Bell and Stuart, 1990), an intergeneric hybrid of possible use as a rootstock for pear or as a parent for the development of a novel fruit type. These studies identified antibiosis and ovipositional and feeding antixenosis as modes of resistance.
Nymphal feeding antixenosis has been associated with increased mortality and delayed development of nymphs (Bell, 1991; Butt et al., 1989; Puterka, 1997) in a limited number of both P. communis- and P. ussuriensis-derived cultivars and breeders selections. The purpose of this study was to further characterize host resistance in additional germplasm of interest for breeding.
BellR.L.1991Ovipositional antixenosis-based host resistance to the pear psylla in Pyrus germplasm of East European originHortScience26710
BerradaS.XguyenT.X.LemoineJ.VanpouckeJ.FournierD.1995Thirteen pear species and cultivars evaluated for resistance to Cacopsylla pyri (Homoptera: Psyllidae)Environ. Entomol.2416041607
ButtB.A.StuartL.C.BellR.L.1988Feeding behavior of pear psylla (Homoptera: Psyllidae) nymphs on susceptible and resistant Pyrus germplasmJ. Econ. Entomol.8113941397
ButtB.A.StuartL.C.BellR.L.1989Feeding, longevity, and development of pear psylla (Homoptera:Psyllidae) nymphs on resistant and susceptible pear genotypesJ. Econ. Entomol.82458461
FolletP.A.CroftB.A.WestigardP.H.1985Regional resistance to insecticides in Psylla pyricola from pear orchards in OregonCan. Entomol.117565573
HortonD.R.KrysanJ.L.1990Probing and oviposition-related activity of summerform pear psylla (Homoptera: Psyllidae) on host and non-host substratesEnviron. Entomol.2113191332
HortonD.R.KrysanJ.L.1991Host acceptance behavior of pear psylla (Homoptera: Psyllidae) affected by plant species, host deprivation, habituation, and eggloadAnn. Entomol. Soc. Am.84612627
LittellR.C.MillikenG.A.StroupW.W.WolfingerR.D.1996SAS system for mixed models. SAS Institute Inc. Cary NC
PasqualiniE.CivolaniS.MusacchiS.AncaraniV.DondiniL.RobertP.BaronioP.2006Cacopsylla pyri behaviour on new pear selections for host resistance programsBull. Insectology5912737
PreeD.J.ArchibaldK.W.KerrK.W.KoleK.J.1990Occurrence of pyrethroid resistance in pear psylla (Homoptera: Psyllidae) populations in southern OntarioJ. Econ. Entomol.8321592163
PuterkaG.L.1997Intraspecific variation in pear psylla (Homoptera: Psyllidae) nymphal survival and development on resistant and susceptible pearEnviron. Entomol.26552558
RobertP.ChaussetJ.Le LézecM.1999Larval development of Cacopsylla pyri (L.) [Homoptera: Psyllidae] on two resistant Pyrus genotypesIOBC WPRS Bull.22108991
RobertP.GuérifP.LemoineJ.Le LézecM.2004Criblage de génotypes du Pyrus vis-à-vis de la résistance au psylle du poirier Cacopsylla pyri (L.)Cahiers Agricultures13349354
RobertP.RaimbaultT.Le LézecM.SimardM.H.2005Resistance of some Pyrus communis cultivars and Pyrus hybrids to the pear psylla Cacopsylla pyri (Homoptera, Psyllidae)Acta Hort.671571575
SAS Institute Inc2013SAS 9.4. SAS Institute Inc. Cary NC
SaxtonA.M.1998A macro for converting mean separation output to letter groupings in Proc Mixed. In: Proceedings of the 23rd SAS Users Group International SAS Institute Cary NC. pp. 1243–1246
ScutareanuP.MaY.ClaeysM.DommisseR.SabelisW.1999Induction of a p-cumarouyl trihydroxy triterpene acid in psylla-infested and mechanically damaged pear treesJ. Chem. Entomol.2521772191
ShaltielL.CollM.2010Reduction of pear psylla damage by the predatory bug Anthocoris nemoralis (Heteroptera: Anthocoridae): The importance of orchard colonization time and neighboring vegetationBiocontrol Sci. Technol.14811821
Shaltiel-HarpazL.SorokerV.KedoshimR.HasonR.SokalskyT.HatibK.Bar-Ya’akovI.HollandD.2014Two pear accessions evaluated for susceptibility to pear psylla Cacopsylla bidens (Šulc) in IsraelPest Mgt. Sci.70234239
Singleton-SmithJ.ChangJ.F.PhilogeneB.J.R.1978Morphological differences between nymphal instars and descriptions of the antennal sensory structures of the nymphs and adults of Psylla pyricola Foerster (Homoptera: Psyllidae)Can. J. Zool.5615761584
van der ZwetT.CociuV.CzarneckiJ.NyekiJ.BlazekJ.1989Collecting Pyrus germplasm in Romania, Poland, Hungary, and CzechoslovakiaHortScience221521
WestigardP.H.WestwoodM.N.LombardP.B.1970Host preference and resistance of Pyrus species to the pear psylla, Psylla pyricola FöersterJ. Amer. Soc. Hort. Sci.953436