6种药剂对黄野螟不同龄期幼虫的毒力测定及林间药效试验

[Objective]Heortia vitessoides is the most serious leaf-eating pest of Aquilaria sinensis.In order to screen the ideal insecticides for the control of H.vitessoides,six commercial insecticides were selected for indoor toxicity determination and forest efficacy test of different instar larvae of H.vitessoides.[Method]The toxicity and forest efficacy of beta-cypermethrin,Helicoverpa armigera nuclear polyhedrosis virus,chlorantraniliprole,dimehypo,matrine and trichlorfon to the second and fourth instar larvae of H.vitessoides were compared by leaf dipping method and spray method.[Result]Except for 0.3%matrine,the toxicity of other insecticides to the larvae decreased with the increase of instar.The toxicity of 0.3%matrine to the second and fourth instar larvae was the highest,and the LC50 was 0.485 and 0.388 mg·L-1,respectively.The toxicity of 4.5%beta-cypermethrin to different instar larvae was quite different.The toxicity of second instar larvae was 7.34 times that of fourth instar larvae,and the LC50 was 7.032 and 51.640 mg·L-1,respectively.The toxicity of 5%chlorantraniliprole was 4.46 times that of fourth instar larvae,and the LC50 was 19.362 and 86.278 mg·L-1,respectively.2 billion PIB/ml of Helicoverpa armigera nuclear polyhedrosis virus,18%bisultap and 30%trichlorfon had little difference in toxicity to different instar larvae.The difference between the second and fourth instar larvae was 1.16,1.35 and 1.31 times,respectively.The LC50 of the second instar larvae was 15.651,74.236 and 107.915 mg·L-1,respectively,and the LC50 of the fourth instar larvae was 18.173,100.375 and 141.871 mg·L-1,respectively.The results of forest efficacy test showed that the efficacy of several insecticides on the larvae of H.vitessoides increased with the increase of pesticide concentration.Except for 5%chlorantraniliprole,the mortality rate of other insecticides on the second instar larvae could reach more than 80.00%on average.Among them,the efficacy of 2 billion PIB/ml cotton bollworm nuclear polyhedrosis virus was the best,and the mortality rate was 90.37～100.00%.For the fourth instar larvae,0.3%matrine had the best efficacy,with a mortality rate of 95.56～100.00%,followed by 2 billion PIB/ml nuclear polyhedrosis virus of cotton bollworm,with a mortality rate of 70.00～100.00%.The efficacy of 5%chlorantraniliprole was the weakest,with a mortality rate of 0.00%at five concentrations.The efficacy of 4.5%beta-cypermethrin was also relatively weak,with a mortality rate of 10.00～58.89%.[Conclusion]The application effect of 6 kinds of pesticides in the young larvae stage was better than that in the old larvae stage.It was suggested that 0.3%matrine or 2 billion PIB/ml cotton bollworm nuclear polyhedrosis virus should be used to control the young larvae stage of H.vitessoides.