The effects of a new pyrethroid insecticide WL‐85871 on foraging honey bees (<i>Apis mellifera</i> L.)

Abstract

Abstract Emulsifiable concentrate formulations of WL‐85871 (‘Fastac’) at 10 and 20 g a.i. ha −1 , parathion‐methyl (MEP) at 500 g a.i. ha −1 , and phosalone at 1200 g a.i. ha −1 were individually applied to flowering mustard during June and July 1982. The applications were made by tractor‐mounted boom‐and‐nozzle equipment to small plots in Normandy, France. Before each application, bee hives were placed adjacent to the mustard plots and fitted with either a pollen trap or a dead‐bee trap. The application of both dose rates of WL‐85871 and phosalone resulted in no increase in bee mortalities and no discernible effect on pollen collection or long‐term hive development. In contrast, the application of MEP resulted in substantial bee mortalities, reduced pollen collection and adversely affected hive development. Both dose rates of WL‐85871 caused a sharp decline in foraging activity immediately after application, followed by a return to normal activity within a few hours. A prolonged gradual reduction in foraging activity occurred throughout the afternoon period after the phosalone application; with MEP, foraging activity fell rapidly to a very low level and remained so for the rest of that day and the following day. It was concluded that the ground application of WL‐85871 at 10 and 20 g a.i. ha −1 had no direct effect on honey bee survival and no observable effect on hive development.