POTENCY, SPECTRUM AND RESIDUAL ACTIVITY OF FOUR NEW INSECTICIDES UNDER GLASSHOUSE CONDITIONS

Abstract

The toxicities of four classes of insecticides, emamectin benzoate (avermectin), chlorfenapyr (pyrrole), fipronil (phenylpyrazole), and tebufenozide (benzoylhydrazide) were compared using an artificial diet assay and a residual efficacy assay against several species of Lepidoptera. Emamectin benzoate was consistently the most toxic insecticide; it was 20- to 64,240-times more toxic than the other compounds tested. The LC90 values for emamectin benzoate ranged from 0.0050 to 0.0218 ug/ml for six species of Lepidoptera. Similarly, chlorfenapyr displayed consistent toxicity to all species, with LC90 values ranging from 1.9 to 4.6 ug/ml. The toxicities of fipronil and tebufenozide varied among the species tested. Fipronil LC90 values varied 501-fold (range, 0.64 to 321.3 ug/ml), while tebufenozide toxicity varied 113-fold (range, 0.24 to 27.1 ug/ml) among species tested. In residual efficacy tests conducted in the glasshouse, all compounds were effective (i.e., >90% mortality) at controlling Heliothis virescens on garbanzo bean at projected field rates and at 1/10 of projected field rates with fipronil and emamectin benzoate. Emamectin benzoate, chlorfenapyr and tebufenozide were effective at controlling Spodoptera exigua on sugar beet at projected field rates. However, mortality with fipronil was reduced to 20% or less at 7 to 14 days after treatment. All compounds at projected field use rates were effective against Trichoplusia ni on cabbage, although tebufenozide was the only compound effective at 1/10 of projected field rate for 14 days after treatment. However, tebufenozide was ineffective against Plutella xylostella at projected field use rates on cabbage while emamectin benzoate, chlorfenapyr, and fipronil were effective. The potential of these compounds for arthropod pest management are discussed.

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