Selection of persistent insecticides for control of Chilo suppressalis in rice seedling stage

The toxicities of 9 commonly used insecticides against the 4th-instar larvae and neonates of Chilo suppressalis were tested by Potter Tower Spraying and Residues on Artificial Diet,respectively.The results showed that abamectinn and chlorantraniliprole were higher in toxicity to C.suppressalis,and followed by hexaflumuron,ethofenprox,chlorpyrifos and phenthoate,but monosultap,triazophos and profenofos were lower.Then,the three insecticides,chlorantraniliprole,abamectin,chlorprifos,were selected as representatives to treat rice seedlings for checking their persistent effect on the neonates inoculated in time course.The results showed that treatment with 5 000 times dilution of 20% chlorantraniliprole SC could keep the rice seedlings from infestation for 14 days,and high doses(1 000 times dilution)could keep for 28 days.One thousand time dilution of 1.8% abamectin EC could keep no infestation for only 7 days,which could be extended to 14 days when 500 times dilution was used.The persistent control effect of 40% chlorprifos EC was poorest of the three insecticides.Only 84.3% in 7 days was observed when 1 000 times dilution was applied.However,the corresponding control effect could be enhanced to 100%,89.5% by using 300 times dilution.It was concluded that chlorantraniliprole and abamectin had good persistent control effect,which could be further enhanced by the use of high doses.Thus,under the prerequisite for no phyto-toxicity,high doses of these two insecticides were suggested for the control of the first generation of C.suppressalis by handling rice seedlings before transplant to enhance the control effect and minimize the following field insecticide sprays.