Hypersensitivity in apple to feeding by Dysaphis plantaginea: effects on aphid biology

Effects on rosy apple aphid (Dysaphis plantaginea) of hypersensitivity to aphid feeding in apple were assessed in a series of insectary experiments in 1980–82. Hypersensitive plants rapidly produced tissue necroses at aphid feeding sites. Inoculation with apterae demonstrated that, in comparison with aphids on susceptible plants, aphids on hypersensitive plants showed symptoms characteristic of host antibiosis, including increased mortality, failure to reproduce and slower development. Embryo number indicated that fecundity of surviving adults was lower on hypersensitive plants and mean relative growth rate of aphids was reduced. Hypersensitivity did not prevent colonisation by gynoparae returning from the summer host, nor subsequent egg-laying. It conferred, however, a strong resistance against colonisation after egg-hatch the following spring. The potential of hypersensitivity as a field-resistance is discussed.