TOPICAL TOXICITY OF IMIDACLOPRID, FIPRONIL, AND 7 CONVENTIONAL INSECTICIDES TO THE ADULT CONVERGENT LADY BEETLE (COLEOPTERA, COCCINELLIDAE)

The relative toxicities (comparing LD(50) and LT(50)s) of two syntheti c pyrethroids (cypermethrin and fenvalerate), two organophosphorus ins ecticides (chlorpyrifos, diazinon), three carbamates (propoxur, carbar yl, bendiocarb), a phenylpyrazole representative (fipronil), and a het erocyclic nitromethylene representative (imidacloprid or NTN 33893) we re assessed with topical bioassays in the laboratory against the conve rgent lady beetle, Hippodamia convergens Guerin Meneville. LD(50) valu es decreased (i.e., toxicity increased) with an increased time after a pplication of a specific insecticide. The differences between the LD(5 0) values caused by various insecticides were significant. Among teste d insecticides, cypermethrin and bendiocarb were the most toxic; fipro nil was the least toxic. H. convergens responded differently to differ ent insecticides within the same class. Beetles exhibited similar resp onses to both organophosphorothionates chlorpyrifos and diazinon 24 to 72 h after application. Of the carbamates, propoxur was 2.4 and 3.5 t imes less toxic than carbaryl and bendiocarb, respectively. Of the pyr ethroids tested, cypermethrin was significantly more toxic than fenval erate. At 800 ppm, cypermethrin and bendiocarb were the fastest in kil ling H. convergens among the tested insecticides. The ranking of insec ticides in decreasing order of LT(50) values was as follows: fipronil > diazinon > chlorpyrifos > propoxur > carbaryl > fenvalerate and imid acloprid.