Influence upon honeybees of chronic exposure to very low levels of selected insecticides in their diet
J. L. Nation, F. A. Robinson, S. J. Yu And A. B. Bolten
Several sizes of hive were treated for colony viability and ease of manipulation when colonies of honeybees were confined within screened cages. Hives containing either a single standard frame (1742 cm2 ) or a single miniature frame (431 cm2) were acceptable, but hives containing a single standard frame were used in our experiments because they were easier to manipulate and produced more brood that could be used for other experimental purposes. A small colony was established in each of several 1·8 x 1.8 x 2.0-m screened cages. Pollen cakes containing 0.017 ppm permethrin, 0.16 ppm malathion, 5.12 ppm methoxychlor, 10 ppm difiubenzuron, 0.17 ppm carbaryl or no pesticide were fed to the colonies to determine the effects on the bees of chronic exposure. During a test period of 10 weeks only methoxychlor caused a significant reduction (P<0.05) in quantity of brood reared, amount of pollen cake consumed, and amount of sucrose syrup stored in the colonies. Diflubenzuron at 10 ppm caused greater than 50% reduction in the amount of syrup stored compared to control colonies, but it did not cause reduction in consumption of pollen or in the quantity of brood reared. In general, colonies fed insecticides accumulated debris and dead bees on the hive bottom because of reduced house-cleaning. Colonies fed methoxychlor or malathion were particularly susceptible to invasion by wax moth.