Exposure Effects on the Productivity of Commercial Bombus impatiens (Hymenoptera: Apidae) Quads During Bloom in Watermelon Fields

In light of population declines of honey bees (Apis mellifera L.), research has refocused attention on alternative pollinators and their potential to fulfill pollination services within economically important agricultural crops. Bumble bees are one such alternative, and within the past 20 yr, these pollinators have been reared and sold as commercial pollinators. Investigation into their use has been limited and more research is needed to improve pollinator effectiveness in field settings. Quad pollination units of the commercially reared native bumble bee species, the common eastern bumble bee (Bombus impatiens Cresson), were monitored and evaluated for productivity during peak watermelon [Citrullus lanatus (Thunberg) Matsumura & Nakai] bloom in southern Delaware. Differing colony exposures including various shade structure designs and natural shade were compared to assess the quality of the shade in regards to bumble bee activity during watermelon bloom. Quads receiving different nest treatments were evaluated on the basis of foraging activity and colony weight gain. Results indicated that colonies within quads provided with artificial or natural shade had significantly more foraging activity, weighed more, and produced more cells than colonies in quads placed in the field with no shade. Colonies within quads provided with artificial and natural shade peaked later in terms of foraging and weight gain, suggesting that growers could extend harvest to take advantage of later markets and possible movement into fields that were planted later.