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- Author or Editor: P. H. Westigard x
- Journal of the American Society for Horticultural Science x
Abstract
Roots of most of the primitive Pynus species were infested with pear root aphid Eriosoma pyricola Bak. and David., and increase or decrease in number noted 30 days later. Although seedling populations varied somewhat, P. amygdaliformis, P. elaeagrifolia, P. syriaca, P. betulaefolia, P. calleryana, P. koehnei, P. ussuriensis, and P. nivalis can be considered resistant. P. communis, P. cordata, P. gharbiana, P. pashia, P. Fauriei, and P. pyrifolia were either susceptible or very variable in resistance. Only P. bucharica, P. dimorphophylla, and P. mamorensis had no resistant seedlings in the lots tested. Interspecific hybrid populations were predictable though variable in resistance.
Abstract
Field and laboratory studies of host preference and resistance of Pyrus species and cultivars to the pear psylla, Psylla pyricola, were conducted in Southern Oregon from 1964–1968. Asian species were generally less attractive to oviposition than those from Asia Minor, North Africa or Europe. Attractiveness of P. pyrifolia and P. communis cultivars was higher than for P. ussuriensis.
Susceptibility of Pyrus was based on differences between total egg deposition and resulting nymphal populations. Using this nymph/egg ratio the results indicated that Asian material was more resistant than material from Asia Minor or Europe. The Asian species P. fauriei and P. calleryana exhibited both a high degree of unattractiveness to oviposition and resistance to nymphal development.