Comparison of honey bee (Hymenoptera: Apidae) mortality as a result of diurnal and nocturnal applications of dimethoate
1990
Byrne, D.N. | Waller, G.D.
Applications of dimethoate in Arizona are currently being made to citrus orchards at night to reduce the hazard to pollinating honey bees, Apis mellifera L. Over a 9-d period, an application of dimethoate sprayed during the day produced a mean number of 13,414 dead honey bees per colony, but an application sprayed at night produced a mean loss of 6,735 honey bees per colony. Over the same 9-d period, colonies in an unsprayed orchard had a mean loss of only 1,792 honey bees. At one point, pollen collection was reduced by 100% in two sprayed orchards but was unchanged in an orchard that was not sprayed. Colonies in an orchard sprayed during the day lost a mean of 9.2 frames of honey bees, whereas those in an orchard sprayed at night lost a mean of 4.2 frames. Colonies in an unsprayed orchard, however, gained a mean of 3.2 frames of honey bees. Honey bee mortality from applications sprayed at night, although significantly lower than the applications sprayed during the day, is probably still at a level unacceptable to beekeepers.
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