Effect on Honey Bees of DDT and thiodan applied from the air as sprays to Chou Moellier

Abstract

Summary A five-and-a-half acre crop of flowering chou moellier was sprayed from the air with a DDT emulsion at the rate of 2 lb of 1007c p.p.i. DDT in 7 gal water per acre. 1.2 lb of 100% thiodan in 7 gal water was applied from the air to one acre of a 25-acre flowering chou moellier crop. Both sprays were applied before bees from nearby apiaries commenced to visit the crops. Bees collected nectar and pollen extensively from the crops which were of maximum attractiveness. Honey bees were repelled by the DDT for 6 days after application, but there was no evidence that it repelled bumble bees. Some mortality occurred in field bees, but it was not very high and hives were not weakened and brood was not affected. It is considered that DDT emulsion, if applied before bees visit a flowering brassica crop, will cause only slight mortality. It should be valuable for use when a crop must be sprayed to save it from destruction by pests. Thiodan exerted no repellency and was more lethal to field bees than the DDT. Although no adverse effect on adult bees or brood was observed in the apiary it is considered that the hives would have been seriously affected if an area of more than one acre had been sprayed. Thiodan should not be applied to flowering brassica crops.