The native pollinators of an apple orchard: variations and significance

Observations on native and domestic insect pollinators were carried out during the blossom period from 1978 to 1980 in a semi-dwarf apple orchard in Ontario. Weather conditions and numbers of blossoms per tree were also recorded. Apis mellifera was the most frequent pollinator for all years. The Anthomyiidae (Diptera) ranked second for 1978 and 1979, but in 1980 the Andrenidae and Halictidae were of greater importance than the Diptera. The efficiency of the pollinators was determined by analysis of the pollen carried on their bodies. Hymenoptera had more pollen on their bodies than the Diptera. Among the Hymenoptera, the Andrenidae and the pollen-gathering Large Andrenidae had the greatest amount of fruit pollen on their bodies. Among the Diptera, the Syrphidae had the greatest amount of fruit pollen. The effectiveness of the pollinators was evaluated by measuring fruit set, seed set and the effective pollination period. There was no significant difference in fruit set between years inspite of adverse weather in 1979. Native insects were important pollinators, particularly in unfavourable weather.