Tolerance of some scab-resistant apple cultivars to the rosy apple aphid, Dysaphis plantaginea

Rosy apple aphid (RAA), Dysaphis plantaginea Passerini (Homoptera: Aphididae), is a major apple pest that is normally controlled by insecticide sprays. The use of tolerant cultivars to reduce damage of this aphid would contribute to a non-chemical crop protection. This study evaluated the susceptibility of nine scab-resistant apple cultivars (‘Dayton’, ‘Freedom’, ‘Galarina’, ‘GoldRush’, ‘Jonafree’, ‘Liberty’, ‘Priscilla’, ‘Redfree’ and ‘Williams’ Pride’) to RAA. Greenhouse trials and field observations were conducted for 2 years. Significant differences were observed among cultivars in aphid abundance and damage level 21 days after an infestation in the greenhouse. ‘GoldRush’ and ‘Galarina’ did not show typical leaf-rolls induced by RAA and were considered tolerant to this aphid species. Some cultivars showed low susceptibility while the cultivars ‘Jonafree’ and ‘Redfree’ turned out to be highly susceptible. Aphid abundance and damage levels were positively correlated. Field surveys confirmed greenhouse results. Growing cultivars resistant to scab and tolerant or only slightly susceptible to RAA would reduce pesticide use and increase opportunities for sustainable apple production.