The toxicities of 11 kinds of insecticides to the diamondback moth,Plutella xylostella and its natural enemy Erigonidium graminicolum

The toxicities of 11 kinds of insecticides to the 3rd instar larvae of the diamondback moth(DBM),Plutella xylostella(L.),and its natural enemy Erigonidium graminicolum(Sundervall),were assayed under laboratory conditions.The results demonstrate that Bt,fipronil,chlorfenapyr,spinosad and diafenthiuron could kill 100% of DBM larvae,followed by chlorfluazuron and cartap which killed 90.0% and 87.5%,respectively.Diafenthiuron,Bt,tebufenozide and chlorfluazuron both showed lower initial and persistent toxicities against E.graminicolum larvae;mortality was 30% after being subjected to a toxic film of these pesticides for 48 hours.In contrast,the other 8 kinds of insecticides,except for avermectin,alpha-cypermethrin and cartap,caused 20% mortality of E.graminicolum adults.Based on these results,Bt,diafenthiuron,spinosad are the best pesticides to control P.xylostella,especially when E.graminicolum is abundant.