THE RESIDUAL TOXICITY TO HONEYBEES OF SOME INSECTICIDES ON CLOVER FLOWERS: LABORATORY STUDIES
S A MANSOUR, A D ALI AND M K AL-JALILI
Residual toxicity to adult honeybees (Apis lIIellifera) of 10 insecticides sprayed on clover (Trifolium alexalldrillulII) at field rates recommended in Iraq was assessed by a simple laboratory method in which caged bees were fed a blend of SO clover flowers in SO ml25% sucrose syrup. For 6 of the insecticides tested, morrality was over 90% in bees fed with syrup blended with flowers collected on the day of spraying. Thereafter mortality declined with time to a negligible level in bees fed syrup blended with flowers collected 7 days after spraying. The rate of decline varied somewhat with the insecticide. Insecticides were compared for hazard to honeybees on the basis of the time required for mortality recorded in a 24-h period to decline to 20%. With this criterion, carbaryl, fenitrothion, propoxur, methomyl and diazinon were the most hazardous of the insecticides tested; dicofol and fen valerate were least hazardous and pirimiphos-methyl, chlorpyrifos and phenthoate were intermediate.