Effect Of Volatiles Emitted From Wilted Populus Nigra L.on Mating And Oviposition Of Helicoverpa Armigera(Hübner)

Wilted leaves derived from salicaceae have fairly strong attractiveness to noctuid moths.Four hypotheses had put forward to explain the mechanism,including providing a shelter or a mating site,attracting both sexes to feed,stimulating sex pheromone production of virgin females,stimulating oviposition of mated females.Although blending screening,carrier optimization,and trap design made a notable progess presently,the attractive mechanism remained unkown.Therefore,the author tested the effect of Populus nigra “Italica”" L.wilted leaves on on several behaviors of Helicoverpa armigera moths,and the results are summarized as follows.(1)Attracting rhythm.Odours emitted from Populus wilted leaves could attract both sexes when tested separately,and the response temporal pattern was similar between sexes.There were three attractive peaks at night,the first one peaked between 21:00 and 22:00,which declined temporarily at midnight,the second one peaked at 0:00-1:00,and the last one peaked at 3:00-4:30.Among them,the first peak was strongest.(2)Effect on mating.When tested separately,both the female moths and wilted Populus leaves could capture male moths.When the one were placed in the upstream chamber and another placed in the downstream chamber,the females played a primary role.However,when the females were placed upstreamly and the leaves downstreamly,number of males captured was extremely significant higher than leaves alone.We concluded that sex pheromone might be absorbed on the surface of the leaves,which prolonged its releasing time at night.(3)Field trapping.Neither H.armigera sex pheromone nor H.assulta sex pheromone could be synerged by Populus leaf extracts.The captures of H.armigera moths were not significantly differed as long as sex lure contained,which were significantly more than Populus extract used alone.Additionally,the floral attractant had generic attractiveness and could overcome the specific drawbacks of sex lures of both species.(4)Ovipositional choices.All plant species,including the non-host Populus and four main hosts(cotton,tobacco,tomato,and hot pepper)of H.armigera,could significantly stimulate egg-laying when paired with clean air.When populus leaves were paired with each host leaves respectively,the eggs deposited on the substrate with odour from populus leaves did not differ from that of tobacco,but were extremely more than those of the remained host leaves.(5)Effects of plant volatile environments and supplemental nutrition level on female lifetime eggs and longevities of both sexes.The significant factor affecting female lifetime eggs and longevities of both sexes was the concentration of sucrose solution,while plant volatiles hadn't any effects on these parameters.A middle leave of sucrose solution(5%)could produce the longest longevity and the most lifetime eggs.All together,neither our laboratory bioassay nor field trapping provided a evidence for the hypothesis of populus leaves affecting mating,however,populus leaves could be a control-released matrix for sex pheromone,thus prolonged the mating time window.The odours emitted from populus wilted leaves could attract egg-laying of the females,but could not affect the lifetime eggs or longevity.The lifetime reproduction mainly depended on supplemental nutrition level,whose determing role was even stronger than that of female body weight(determing factor of potential reproduction).