# Seasonal and Interannual Variability in the Insect Pest Damage and Beneficial Insect Populations Across Apple Orchards of Different Ages

## TL;DR

This study examines how seasonal and yearly changes affect insect pests and beneficial insects in apple orchards of different ages and structures.

## Contribution

The study reveals that beneficial insects are more influenced by orchard structure than pest populations, which are driven by seasonal and climatic factors.

## Key findings

- Pest populations are primarily driven by seasonal and climatic factors.
- Beneficial insects are shaped more by local habitat features and orchard structure.
- Weak correlations between pests and their natural enemies suggest predators depend on more than just pest abundance.

## Abstract

Insect pest management in apple orchards increasingly relies on biological control strategies to sustainably suppress pest populations while minimizing environmental and chemical inputs. The study objectives were to determine how season, year, orchard structure, and apple varieties influence the occurrence of insect pests and beneficial insects, and to assess the strength of correlations between pest damage and natural enemies, and among natural enemy taxa. Experiments were performed in two consecutive years in three different-aged orchards, and on 11 varieties, where insect damage and the number of natural enemies were observed. All sites were managed according to integrated pest management (IPM) guidelines, and no unmanaged or untreated control plots were included. The main pests were the codling moth, the summer fruit tortrix, the leafminer moth, and the apple blossom weevil; however, their damage could be maintained at low levels. Among natural enemies, aphidophagous arthropods dominated. Pest populations are primarily driven by seasonal and climatic factors, while beneficial insects are shaped more by local habitat features and orchard structure. Our findings should be of broad interest to entomologists, agroecologists, and practitioners of sustainable fruit production.

Apple is one of the most important fruits worldwide; in addition, it constitutes nearly 60% of Hungary’s total fruit production. Presently, the challenge in pest management is not only the decreased range of pesticides, but also the deeper knowledge of natural enemies occurring in fruit plantations, and in their neighborhood. Our objective was to study how season, year, orchard structure, and varieties influence the occurrence of insect pest damage and beneficial insects in apple. We also investigated the strength of correlations between pest damage and natural enemies, as well as among the different natural enemy taxa. The experiment was conducted in three apple orchards, and the damage of insect pests and the number of natural enemies were monitored across ten trees/varieties/sectors/dates. All sites were managed according to integrated pest management (IPM) guidelines, and no unmanaged or untreated control plots were included. Significant differences were observed among orchards and years for all taxa, except Cydia pomonella (L.) among orchards and Orius spp. among years. Pest populations are primarily driven by seasonal and climatic factors, while beneficial insects are shaped more by local habitat features and orchard structure. No effect of the varieties on insect damage could be detected, whereas the abundance of beneficial organisms differed significantly among varieties in more cases. The weak correlations between pests and their natural enemies suggest that the presence and activity of predators depend not only on pest abundance but also on other interrelated ecological factors in intensive apple orchards. The damage caused by C. pomonella could also be kept at a low level in all orchards when appropriate pest management technology is applied.