Cucurbit Genetics Cooperative Report 3:48 (article 28) 1980

Comparison of Squash and Honey Bees as Pollinators of Summer Squash

Vincent J. Tepedino

Utah State University, UMC 53, Logan, UT 84322

Observations and experiments were conducted to ascertain if the specialized squash bee Peponopis pruinosa is superior to the honey bee Apis mellifera as a pollinator of summer squash, Cucurbita pepo, var. Italian Black Zucchini. The study site was the Greenville Farm operated by Utah State University at North Logan, UT. Natural populations of P. pruinosa have been recorded there since 1953 and since honey bees are common, it was not necessary to import hives for experimental purposes. Three parameters contributing to pollination efficiency are: 1) the number of visits necessary to achieve pollination, 2) the preference of the bees for staminate or pistillate flowers, and 3) the average time spent foraging on a flower.

Bagging and controlled visit experiments showed individual visits to pistillate flowers by each species to be equivalent. Honey bees display a significant preference for pistillate flowers; squash bees prefer staminate flowers. Squash bees work the flowers more rapidly than do honey bees. When all parameters are considered, there appears to be little difference between the species as pollinators of squash. However, because of their earlier diurnal flight periods, squash bees were responsible for most pollinations before honey bees appeared in numbers on the plantings.