FIELD AND LABORATORY TESTS ON THE EFFECTS OF CYHALOTHRIN ON ADULTS OFAPIS-MELLIFERA, MEGACHILE-ROTUNDATA AND NOMIA-MELANDERI

The toxicity of cyhalothrin to adults tended to be least to the alkali bee Nomia melanderi (LD50 = 0.036 mu g/bee), intermediate to the hone y bee (Apis mellifera) (0.022 mu g/bee) and greatest to the alfalfa le afcutter bee (Megachile rotundata) (0.002 mu g/bee), both in topical t ests and in residue tests. Adding an adjuvant to cyhalothrin sprays ch anged the toxicity of cyhalothrin to bees in residue bioassay studies with varying results with adjuvant and species of bee. Cyhalothrin at as little as 2 ppm in syrup feeders caused a reduction in honey bee vi sitation. Spraying cyhalothrin at 0.028 kg a.i/ha on flowering alfalfa resulted in significant reductions in populations of alfalfa leafcutt er bees at nesting blocks.