Effect Of Insect-derived Volatiles,Ultra-sonic Wave,and Host Contact Experience On The Ovipositional Behavior Of Helicoverpa Armigera

Helicovera armigera is one of the most serious crop pests.Along with the spread of transgenic cotton in North China,H.armigera has been effectively controlled.However,H.armigera is a highly polyphagous species and still remains as a serious threaten to crops such as maize,tobacco,tomatoes and sunflowers,and not all of these crops are permitted to genetic improvement.Therefore,green prevention and control techniques based on behavioral regulations of mating,oviposition and feeding are still necessary options.Oviposition behavior is closely related to the damage of H.armigera,so the author studied the effect of insect-derived volatiles,ultra-sonic wave,and host contact experience on the ovipositional behavior of H.armigera.The main results are summarized as follows:1.I tested the effect of odors emitted from H.armigera females or males at different densities on the total eggs laid and oviposition choice response of females in bioassay setups of different lengths.The result shows that the stimulation of colony rearing on oviposition only held true in several special treatment combinations.Among the 19 treatments with male moths as odor source,there was only one case showing significant oviposition attraction(50 cm,4 male moths as odor source)and one significant oviposition repellent(12.5 cm,8 male moths as odor source).Among the 20 treatments in which female moths were used as odor source,4 cases showed significant eggs’distribution difference,and all of them were attractive(12.5 cm,4 or 16 virgin female moths as odor source;25 cm,2 females as odor source;50 cm,8 females as odor source).Between-group comparison shows that total eggs laid by subject females laid the most eggs with 16 females placed in 12.5 cm length bioassay setup as odor source,which was a very special combination of conditions.A male placed in 6 cm bioassay setup was another specific combination that stimulated the subject female moth to lay eggs.Further tests using moth pairs or sex lure as odor sources show that all of these treatments did not significantly affect ovipositional choice response or total eggs laid of a subject female.2.I tested the effects of ultra-sonic waves with 100 dB intensity,0-36 kHz frequencies and different trigger modes on the eggs laid of H.armigera mated females.It was found that trigger mode was the most significant parameter affecting eggs laid.Among them,the least number of eggs laid by H.armigera was in the ultra-sonic environment of swept-frequency signal and sinusoidal wave.3.I tested the ovipositional choice response between cotton and tobacco leaf options of females exposed to cotton leaves,tobacco leaves or a mixture of both leaves.The following conclusions were found:(1)both tobacco leaves and cotton leaves could induce positive ovipositional preference;(2)Induction strength of tobacco was much stronger than cotton;(3)compared with the subject H.armigera exposed to a single leaf type,the ovipositional choice response of the subject H.armigera exposed to mixed leaves tended to be intermediate;(4)It took up 6 days to induce a statistically significant ovipositional choice response,covering the main oviposition stage after emergence.In addition,laboratory bioassay setup restricted the subject to exposure to other plant leaves,so the positive experience effect seems not likely occurs in nature.