The Effect of DDT Dusting on Honeybees

Abstract

In an area 2 miles square near Blythe, Calif., containing a limited acreage of pollen and nectar sources and in which the honeybee population was controlled, the effects of DDT dusting on honeybees were carefully studied. The effects at the hives were studied by following changes in wt., pollen-collecting activity, flight lanes, size of cluster in early morning, number of dead bees in front of each hive, brood counts, and honey production. The effects were studied in the field by counts of bee and lygus population, visual observations, and mortality of field bees held in small cages. It was shown by marking that most of the bees from the exptl. hives were visiting one alfalfa seed field, and also that the majority of the bees in this field were from the exptl. colonies. This field was dusted 3 times with 30 lb. of 5% DDT dust per acre per application. It was demonstrated that such dusting of alfalfa in bloom has a detrimental effect on the production and activity of honeybees. Although this effect is definite it is small and is more than offset by the increased nectar flow when lygus bugs are controlled. The marked decline in bee populations in a dusted field immediately after treatment would seem to be largely due to repellent action of DDT dusts. Even though the effect on the bees is not great, dusting of alfalfa in bloom should be restricted to the essential minimum and should only be done in the early morning before the bees are active.