Toxicity of insecticides to diamondback mothPlutella xylostella(L)

Abstract

Abstract Dosage-mortality relationships for permethrin, fenvalerate, methamidophos, and carbaryl against diamondback moth, Plutella xylostella (L.) were determined under laboratory conditions by caging larvae on broccoli leaf discs, which had been sprayed under a Potter tower, and by spraying adults directly. LC50 values were determined at 48 h. The toxicity of permethrin and fenvalerate to third instar larvae was 10 to 160 times more than methamidophos and carbaryl respectively. Permethrin and fenvalerate were 2 to 260 times more toxic than methamidophos and carbaryl respectively. The effect of post-treatment temperatures of 15°C and 25°C on the toxicity of the 4 insecticides to larvae was also determined. A marked increase in toxicity of pyrethroids, and decrease in toxicity of carbaryl, was observed at 15°C.