Evaluation of bee susceptibility to several reduced-risk and microbial pesticides

With bee health and population declines now a worldwide concern, research on acute and sub-lethal toxicity of pesticides to bees is critical to ensure sustainable agroecosystems. We evaluated the toxicity of several reduced-risk pesticides and biopesticides used or projected for use in lowbush blueberry (Vaccinium angustifolium) to Bombus impatiens Cresson (bumble bees) and Megachile rotundata Fabricius (alfalfa leafcutting bees), managed species often used by growers for pollination. Bee susceptibility in the laboratory depended greatly on the pesticide to which bees were exposed and the bee species. The ascending order of toxicity to leafcutting bees through direct contact exposure was Belt (flubendiamide; essentially non-toxic) < Imidan (phosmet) < Delegate (spinetoram) ≤ Success (spinosad) < Decis (deltamethrin). The same trend was observed for bumble bees, albeit at higher lethal concentrations. In addition, bumble bees were much more susceptible to Delegate and Decis through ingestion than direct contact. Sub-lethal micro-colony studies were conducted on bumble bees using the microbial biopesticides Serenade (Bacillus subtillis) and Botanigard (Beavaria bassiana) and the reduced-risk insecticide Movento (spirotetramat). Movento caused high mortality after a week and Serenade reduced drone production when ingested. Serenade, Botanigard and Movento had no significant impact on micro-colony development when applied topically. The responses of these bee species to different products emphasize the importance of avoiding generalities when drawing conclusions on the hazards of pesticides to various bee species.