Cultivar-mediated effects on apple–Dysaphis plantaginea interaction

The question of whether food webs are resource or predation controlled is crucial for the development of sustainable IPM strategies in agriculture. Many IPM studies focus on top–down control, while little is known about bottom–up effects. Here, we unravelled the bottom–up interactions between rosy apple aphid (RAA) Dysaphis plantaginea and 13 apple cultivars in north-eastern Belgium. Population dynamics, apple leaf damage, preference and performance measurements were used to determine the interactions between RAA and apple cultivars. Seasonal abundances and RAA-infested shoots were significantly affected by the cultivar. The cultivars Fuji, Granny Smith, Jonagold and Cripps Pink harboured clearly higher numbers of aphids compared to other cultivars, especially Red Delicious. Regarding leaf damage degree, Fuji was significantly the most impacted, while the lowest damage was recorded on Red Delicious. The potential apparent competition among apple cultivars was evaluated using RAA overlap diagrams. By acting as a potential source of RAA, a particular cultivar can considerably affect other nearby cultivars. In host selection bioassays, significant differences in the choice behaviour of RAA were found in the laboratory for different apple cultivars. Other important findings from the reproduction–offspring performance bioassays revealed that while Fuji stimulated high production of nymphs, their development remained retarded on Fuji, compared to especially Boskoop on which significantly lower numbers of nymphs occurred. Our study provides a promising insight into the importance of studying apple–RAA interactions within an eco-friendly RAA management tactic.