Chemcal Identification And Effcts Of Oviposition-Deterring Pheromones(ODPs) From Eggs Of The Cotton Bollworm, Helicoverpa Armigera (Hübner) (Lepidoptera: Noctuidae)

As a world-wide pest, the cotton bollworm Helicoverpa armigera (Hiibner) is undoubtedly an important cotton pest in China. There were serious outbreaks in the cotton area of Northern China from 1990 to 1994 because of resistance to synthetic chemical insecticides. As a new method of the cotton bollworm management, oviposition-deterring pheromone (ODP) had some benefits. This method, for example, had no poison to non-target creatures and no pollution to environment. In recently research, ODP of the cotton bollworm was found to be associated with tarsi of adult female and the larval frass. The chemical component of the ODP was plamitic and oleic acid. Is ODP also originated from eggs? Where is the production site of this pheromone? In this paper, I intend to answer these questions.1. EAG response was studied to egg and the hexane extract to the surface of eggs. It was found that the EAG response of female of the cotton bollworm to egg smell and hexane extract smell was 3.5716 and 6.0712 mV respectively, significantly greater than that to control (1.9362 mV). Similarly, the male was 3.8484 and 7.3558 mV respectively, comparing to only 1.5452 mV to control. The result showed that there were some EAG active chemicals associated with conspecific eggs and could be extractable with hexane.2. The hexane extracts to egg surface and egg yolk were analyzed for lipid classes by spotting an aliquot on an 8 10cm thin-layer chromatography plate (TLC). After coloration with Iodine vapor, one band was visualized. This band had similar Rf value to a blend of synthetic fatty acids and demonstrated that this band should be fatty acids. When the hexane extracts to egg surface and egg yolk were separated into Iodine-colorated band and Iodine-uncolorated mixture and re-collected from TLC plate,only the former exhibited significant EAG response by both female and male adults of cotton bollworm. Thus indicated that the EAG active chemicals in hexane extracts from eggs was actually the fatty acids.3. After derivatization with BSTFA, the Iodine-colorated band from the hexane extract to egg surface was analyzed by GC-MS. The main components were four fatty acids: myristic, palmitic, stearic, oleic acid, with composition of 0.66, 0.22, 0.11 and 0.01.4. The EAG response and deterring effects of the four synthetic fatty acids were determined. Both female and male adults of cotton bollworm exhibited significant EAG response to each of the four fatty acids and to a blend of palmitic and oleic acid. Among the four fatty acids, plamitic, oleic acid and a blend of plamitic and oleic acid elicited greater EAG response than myristic and stearic acid. The oviposition-deterring effect of synthetic blend of the four fatty acid was tested at the ratio found on the surface of eggs (myristic : palmitic : stearic : oleic=0.66 : 0.22 : 0.11 : 0.01). The blend significantly deterred oviposition in the cotton bollworm. ODI and the average deterrent rate were 0.3507 and 0.48 respectively. It is concluded that the natural oviposition-deterring pheromone from the cotton bollworm eggs is a mixture of myristic, palmitic, stearic, and oleic acid.On my thesis, the active components of oviposition-deterring pheromones were identified on the surface of eggs in Helicoverpa armigera. Their bioactivity was studied too. This research is important for potential application.