Management factors strongly affect flower-visiting insects in intensive apple orchards

Context: Pollination is an essential ecosystem service, and primary pollinators such as insects are largely declining. Agricultural intensification is one of the main drivers of such decline. The globally relevant apple production depends on this service. Apple orchards are often cultivated intensively over large monocultural landscapes, which are unsuitable for many pollinating species. Identifying and implementing appropriate management measures for pollinators is key to maintaining crop productivity and promote biodiversity. Objective: We investigated the abundance of flower-visiting insects in intensive apple orchards in northern Italy. We assessed whether the abundance of flower-visiting insects, underpinning pollination, is affected by seasonal and weather patterns, and by fine-scale management variables. Methods: We sampled 70 sites scattered all over the study area and counted five times flower-visiting insects (assigning them to broad taxonomical groups) at three randomly selected plots per site between April and September. We distinguished between insects visiting wildflowers and apple blossoms and assessed their response to ground and orchard management, and to variables describing the weather and season progression. Results and conclusion: Honey bees were the dominant group (followed by wasps and ants, flies and syrphids), and their abundance negatively affected that of wild bees. Hour, date, and temperature (and the interaction between the latter two) were important for many groups and overall insect abundance. The presence of spontaneous flowers on the ground (both abundance and richness) positively affected the total number of insects on both wild and apple flowers, and of many single groups of flower-visiting insects. A taller grass sward positively affected many groups and all flower-visiting insects. Frequent mowing tended to promote the number of apple flowers’ visitors, probably due to the lack of other flowers, but it also resulted in a negative effect on honey bees foraging on wildflowers. The presence of anti-hail nets negatively influenced the abundance of all insects and of many groups visiting flowers. Significance: Management and conservation efforts should focus on ground vegetation and specific management practices (tillage, netting) to support more diverse pollinator communities, increasing biodiversity and lowering the dependence of apple yields on a single pollinating species. The presence of wildflowers and plant species richness in the ground cover is crucial, as it was a major driver of the pollinators’ community. Enhancing the ground vegetation in orchards through sustainable management appears to be an effective management practice to sustain wild pollinators and, potentially, the pollination of apple trees.