Roles Of Volatiles On The Host Selection Of Chilo Suppressalis Walker,Cnaphalocrocis Medinalis Guenee And Their Parasitoids Cotesia Chilonis Matsumura,Cotesia Ruficrus Haliday

The mediation role of volatile chemicals on the orientation of two herbivores, rice striped stembore(SSB), Chilo suppressalis Walker, rice leaf folder(RLF), Cnaphalocrocis medinalis Gueene and their larval parasitoids Cotesia chilonis Matsumura, Cotesia ruficrus Haliday were studied. The volatile chemicals from various plant-herbivore-complexes were collected and identified using SPME-GC-MS The results are summarized as follow:1) The orientation behavior of the female adults of SSB and RLF to the volatiles from rice plants treated differently were studied with a behavioral observing chamber and the preference of the female for oviposition between different rice plant-herbivores complexes was also studied with an egglaying chamber. The adult females both SSB and RLF were attracted by the volatiles from the rice plants significantly. The female adults of SSB and RLF preferred the volatile from healthy rice plants to that from the rice plants damaged by SSB or RLF larvae and laid more eggs on the healthy plants except that the RLF adult females had the same preference to volatiles from RLF damaged rice plants as to that from the healthy rice plants and laid the same amount of eggs between the two plants. In one choice test, the 1st and 3rd instar larvae of SSB were significantly attracted to the volatiles from both healthy and herbivores damaged rice plants. But in double choice test, the preference of larvae to the volatiles between them was of no significant difference.2) The orientation response of C. chilonis and C. crucifirus to the volatiles from rice plant, two herbivores, their frass and their damaged rice plants were studied with a Y type tube. The females of the two parasitoids were remarkably attracted by the volatiles from all above sources. They were able to differentiate between the volatiles from the rice plants with herbivores and that from the rice plants without herbivores and much more wasps selected theformer. The volatiles from the herbivores being damaged rice plants were more attractive to the two wasps than that of the healthy plants with herbivores (not infest). It suggested that wasps were not only attracted by the volatiles from the rice plants, herbivores and their frass, but also by a synergism among the volatiles from the rice plants, herbivores and herbivores damaged rice plants. Between the volatiles from the healthy rice plants and the mechanically damaged rice plants, the buffer treated plants and the plants treated with the salivary of one of the two herbivores, the numbers of wasps to both side were not significantly different. It suggested that the mechanical damage and the salivary of the two herbivores could not induce the rice plants to emitted off volatiles to attract the two parasitoids.3) The intra- and interspecific interactions between the two parasitoids were studied with a Y type tube. The female wasps of C. chilonis were not able to differentiate the healthy SSB larvae from the parasitized larvae according to their volatiles except the larvae parasitized by C. chilonis for 5d.4) More than 30 components were trapped from headspace of rice plants infected by the herbivores with solid phase micreoextraction (SPME), among which 25 components were identified with GC-MS. They were 10 aliphatic saturated hydrocarbons, 11 terpenes, 2 aldehydes, one unsaturated aromatic hydrocarbon and one ketone. Some kinds of terpenes were newly found in rice plants. The amounts of volatiles and relative contents of these components in different rice plants were analyzed by GC. The amounts of volatiles from the SSB or RLF damaged rice plants and the larvae removed rice plants were much more than that from the healthy or mechanically damaged rice plants. The relative contents of some terpenes such as Caryophyllene, p-Sesquiphellandrene, Dodecatriene, P- Humulene, l,6,10-Dodecatrien-3-ol in SSB damaged rice plant volatile were much higher. The relative contents of Ul, Cyclohexene-l-methyl-4-(5-methyl-l-methylene-4-hexenyl), p-Humulene, Naphthalene,...