Residual Life and Toxicity to Honey Bees (Hymenoptera: Apidae) of Selected Insecticides Applied to Cotton in Arizona

Abstract

The residual life and toxicity to foraging honey bees, Apis mellifera L., of 17 insecticides (12 pyrethroids, 4 organophosphates, and 1 formamidine) applied to cotton, Gossypium hirsutum L., in Arizona were examined over time up to 21-d after application in a series of four tests during a 3-yr period (1985-1987). Organophosphate residues disappeared rapidly from cotton leaf surfaces with 5% at 15 d after application. Residues remaining from the September applications were higher than from the July applications. The addition of chlordimeform to permethrin did not significantly affect the residual life of permethrin nor did it affect the significance of the cis -and trans -isomer relationships to each other. It did, however, change the significance of the isomer relationships to other pyrethroids. Honey bee mortalities of 85-100% from leaves freshly treated with organophosphates were higher than from any other insecticides except for bifenthrin emulsifiable concentrate (100%) and wettable powder (95%) and permethrin with chlordimeform (95%) and without chlordimeform (89%), Except for encapsulated methyl parathion, the insecticides tested were safe for forager bees 3 d after application. One day after application permethrin plus chlordimeform gave 84% mortality compared with 47% with no chlordimeform. This synergism was not seen on subsequent days. On two occasions, bee mortality was greater from cyfluthrin-treated leaves the day following treatment than immediately after treatment. This contradicts data from residues where insecticide levels were higher immediately after treatment than the day following treatment.