Andreev, R., & Kutinkova, H. 2004a Resistance to aphids and scale insects in nine apple cultivars.. Journal of Fruit and Ornamental Plant Research 12 (Sp. Iss. SI): 215-221.

Notes: From 2001 to 2004, nine apple varieties were evaluated in terms of their resistance to infestation by three species of aphid and three species of scale insect. 'The cultivars evaluated were 'Bell Golden', 'Cooper Sel. 4', 'Granny Smith', 'Melrose', 'Morspur Golden Delicious', 'Mutsu', 'Primrouge', 'Starkrimson' and 'Vista Bella'. The aphid species studied were Dysaphis plantaginea Pass., Dysaphis devecta Walk. and Aphis pomi De Geer, all from the family Aphididae. The scale insects studied were Diaspidiotus perniciosus Comst. And Lepidosaphes ulmi L. from the family Diaspididae, and Eulecanium mali Schr. from the family Coccidae. The trial was carried out in a fourteen-year-old orchard which belongs to the Agricultural University at Plovdiv, Bulgaria. The resistance of the cultivars to a particular pest were based on the the level at which their shoots were infested with that pest. The cultivar most resistant to infestation by aphids was 'Bell Golden', followed by 'Starkrimson', 'Melrose', 'Morspur Golden Delicious', 'Mutsu', 'Cooper Sel. 4', 'Granny Smith', 'Vista Bella' and 'Primrouge'. All of the cultivars were infested by scale insects during the winter, but to varying degrees. The cultivar most resistant to infestation by scale insects was 'Starkrimson', followed by 'Morspur Golden Delicious', 'Bell Golden', 'Melrose', 'Granny Smith', 'Vista Bella', 'Primrouge', 'Mutsu' and 'Cooper Sel. 4'. Starkrimson' was resistant to infestation by both aphids and scale insects.