Aphid proliferation in orchard alleys and canopy predator aggregation in eastern German apple orchards

1. European apple (Malus domestica) orchards face persistent threats from aphid infestations, which can severely compromise fruit yields.

2. In this study, we compared aphid communities in two microhabitats (tree canopy and orchard alley) in commercial apple orchards under organic and integrated pest management (IPM), in relation to aphidophagous predator abundance at three stages of the growing season: early fruit development, fruit maturity and post-harvest.

3. We sampled eight organic and eight IPM apple orchards in eastern Germany using standardised canopy beating of apple trees and suction sampling in the orchard alleys.

4. Our results indicate no significant differences in aphid infestation between organic and IPM orchards, regardless of the sampled microhabitat. However, aphid communities in the tree canopy of organic orchards exhibited greater evenness across species than those of IPM orchards. Eriosoma lanigerum consistently dominated canopy aphid communities across both management systems, highlighting the need for targeted management practices for this pest. Additionally, aphidophagous predator abundance in the tree canopy increased over time and showed a positive association with aphid abundance. Aphid community structure varied significantly across sampling periods and microhabitats. Differences between organic and IPM orchards were observed during the early fruit development phase in orchard alleys, with higher levels of infestation in organic orchards. Aphid taxa such as Macrosiphum euphorbiae, Dysaphis spp., Aphis spiraecola and Rhopalosiphum insertum contributed to these differences.

5. Our findings provide a better understanding of the temporal dynamics of aphid communities in apple orchards in eastern Germany, highlighting the importance of microhabitats and host plant phenology.