EFFECTS OF SELECTED INSECTICIDE FORMULATIONS, PHASED APPLICATION AND COLONY MANAGEMENT STRATEGIES ON HONEY-BEE MORTALITY IN PROCESSING SWEETCORN

These studies were undertaken to evaluate different strategies for red ucing losses of honey bees (Apis mellifera) due to the use of insectic ides in commercial sweetcorn (Zea mays) production fields. The strateg ies were: (1), insecticide application timed to avoid peak flowering p eriods in sweetcorn; (2), insecticide formulation, including carbofura n, encapsulated methyl parathion, permethrin and a tank mix of carbary l plus parathion; (3), the use of pollen traps to prevent contaminated pollen coming into the hive; and (4), feeding (engorgement) of coloni es with sugar syrup immediately following insecticide application to r educe honey bee foraging. Timing of insecticide applications was ineff ective and a practical impossibility. Bee mortality was less with perm ethrin than with the other materials tested. Pollen traps and colony f eeding may reduce bee mortality under some circumstances; however, the se strategies proved unreliable and further study is needed. The data show that bees foraging on ragweed (Ambrosia spp.) adjacent to sweetco rn fields, rather than on sweetcorn, may be responsible for generating the excessive bee losses associated with sweetcorn. The results furth er indicate that circumstances in each field are unique due to prevail ing conditions at each site, e.g. clean cultivation, competing resourc es, insecticide tank mixes, and other nearby applications. Finally, we find it highly significant that we were unable to induce high levels of bee mortality by applying our test compounds at the rate given by t he manufacturers.