The Trapping Mechanism Of Vetiveria Zizanioides On Sesamia Inferens(Walker)and Its Application In Rice Field

Sesamia inferens(Walker)(Lepidoptera:Noctuidae)is a polyphagous insect pest and widely feeds on gramineous plants,including rice,bamboo,maize,sorghum,wheat and so on.In recent years,S.inferens has gradually become a major threat to rice production in the Yangtse delta.At present,the control of S.inferens is primarily dependent on the application of insecticides.However,the insecticides could not reach the damage position so that the control efficiency is not very perfect.The strong insecticide selection pressures accelerate the produce of insect resistance to pesticide and lead to environment pollution.Hence,it is important to find a safety and efficiency control measure for S.inferens.Vetiver(Vetiveria zizanioides),as a trap plant of Chilo suppressalis(Walker)has been studied,however,there was no report on the ecological fitness of S.inferens to vetiver and rice.In this study,we investigated the oviposition habitat of female adults,feeding tropism and feeding amount of larvae,the effect of vetvier on the the survival rate of S.inferens and the activities of four digestive enzymes,three detoxifying enzymes and one target enzyme.In addiotion,we further assessed the integrated control efficiency of vetiver and other control measures.The results were as follows:1.The taxis of S.inferens to vetiver and rice The habitat of female adults between vetiver and rice was investigated underlaboratory conditions.The results indicated that 66,67%female adults selected vetiver to lay eggs after 72 h.The egg average values were 286.50±50.28 and 70.88±26.02 on the vetiver and rice,respectively.The egg number on vetvier was 4-fold higher than that on the rice.In addition,the neonates and 3rd instar larvae prefer to vetiver and 79.17%neonates and 71.25%3rd instars larvae selected vetiver as their food afer 72 h.2.The effect of vetiver on the development of S.inferensWe determined the effect of vetvier on the development and mortality of S.inferens.Our results indicated that the survival rate of S.inferens on vetiver is significant lower than that on the rice.The developmental duration of S.inferens on vetiver was higher than that of on the rice and the developmental duration prolonged 1 d for each instar.The weight of each instar larvae on vetiver was significant lower than that of on the rice.Our results indicated that vetiver can significant reduce the population and restrain the development of s.inferens.In addition,the feeding amount of 3rd instars larvae on vetiver was 20 mg higher than that on the rice.For the AD and RCR,the S.inferens on the rice were much higher than that on the vetiver,and these results also indicated that the development of 3rd instars larvae was inhibited by vetiver.3,The effect of vetiver on the enzyme activities of S.inferensWe used vetiver and rice to feed on S.inferens and determined the activities of four digestive enzymes,three detoxification enzymes and one target enzyme during 1st to 4th instar larvae of S.inferens.Our results showed there were significant differences in the specific activities of digestive enzymes,including protease,amylase,trehalase and sucrose enzymes.For the detoxification enzymes,specific activity of GSTs in the 2nd to 4th instar larvae fed on vetiver was significantly higher than that fed on rice.However,the specific activities of P450 and CarE had no significant difference in each instar larvae of S.inferens.For the target enzyme,the specific activities of AChE showed significant differences in the 1st to 3rd larvae,and in the 2nd larvae fed on vetiver,the AChE acti,vity was 2.9-fold higher than that on the rice.4.The assessment on the integrated control efficiency of vetiver and other control measuresWe assessed the the integrated control efficiency of vetiver and other control measures in the field.Our results indicated that the vetiver can trap S.inferens effectively.And 3 m close the distance to the vetiver,the control efficiency was best.These results further verified our results in the laboratory.If vetiver as the trap plant combined with other control measures,such as sex attractant,the control effect will be better.