Spatial and seasonal patterns of potential orchard pollinators across a Lake Ontario gradient

Pollination in apple orchards depends on insect activity during a short and weather‐sensitive bloom period. Flower‐visiting insect assemblages may vary across orchard gradients in microclimate, bloom development and habitat structure, but fine‐scale spatial and seasonal patterns during apple bloom remain poorly understood.

We examined how flower‐visiting insects in a Lake Ontario apple orchard varied with distance from the lakeshore, trap height and apple flowering phenology.

With blue vane traps placed at approximately 10 cm and 1 m above the soil surface across transects spanning 23–1140 m from the lakeshore, we collected >14,000 insects during 11 weeks, of which 12% belonged to bee and fly genera classified as likely flower visitors. Temperature loggers were placed 10 cm belowground and at 1 m height.

Aboveground temperatures were consistently warmer than belowground, and inland warming was more evident at 1 m. Flies declined more steeply than bees with increasing distance from the lake and increased more rapidly through the season; both groups were more abundant and taxonomically richer in elevated traps. Among common genera, Lasioglossum, Agapostemon, Andrena and Apis corresponded most closely with apple bloom timing.

Potential pollinator assemblages were spatially and seasonally structured, with common bee genera tracking blooms more closely than flies. These results suggest that pollinator availability during apple bloom depends not only on the presence of flower‐visiting taxa in orchards, but also on their seasonal timing, flight height and spatial distribution during the narrow pollination window.