Responses Of Striped Flea Beetles Phyllotrta Striolata(F.) To Their Body And Host Volatiles

The striped flea beetle, Phyllotreta striolata(Fabricius)(Coleoptera:Chrysomelidae), is an important pest species of cruciferous vegetables. Although various high dosage synthetic insecticides, such as chlorpyrifos, phoxim, malathion have been used to protect field vegetable, efficient and acceptable methods of controlling this insect are still lacking because of the development of the insecticide resistance and environment pollution.Hence, safe and environment friendly methods are needed to cope with these ongoing problems. A major strength of pheromones is their effectiveness as part of integrated pest management(IPM) schemes, because of their compatibility with biological control agents and other beneficial invertebrates such as bees and spiders.The objective of this research is to identify the aggregation pheromone of the Southern China population of P. striolata; to identify the attractive compounds against P. striolata from volatiles of host plant Brassica juncea; and to find out how host plant volatiles interact with the pheromones to attract P. striolata by choice experiments in laboratory and field. Methodology and findings are summarized:1. Volatiles of male and female adults of striped flea beetle were collected by solid-phase microextraction(SPEM) method respectively, and then identified and compared with GC-MS technology. The results showed that male and female volatile chemicals belonged to alkanes, olefins and alcohols. The main components belonged to alkanes and olefins. Among them, 2- isopropyl-5- methyl-1- enanthol and 2,4- two methyl-1- decene were most abundant in both male and female. But the substances from male and female had a lot of differences. There were 12 kinds of volatiles existed only in the female, and 25 only in male. In addition, the contents of the same chemicals from male and female were also different.2. Volatiles of the striped flea beetle- fed and un-fed leaves of host plants mustard(Brassica juncea Lee) were also collected and compared by SPEM and GC-MS methods.The chemicals belonged to esters, oximes, alkanes and aldehydes. Among them, esters and oximes were most abundant. The substances from fed and un-fed leaves also had a lot of differences. Two substance, dimethyl phthalate and diethyl phthalate were both in high content and present in both fed and un-fed leaves.3. EAG test was used to select the male specific compounds. The result showed that isopulegol and nonanal could cause electroantennogram responses of P. striolata. The four arm olfactormeter was then used to determine the olfactory response of striped flea beetle adults to these compounds. The results showed that the two substances had different effect in different concentration and flow rate, and the reactions of male and female to the same concentration and flow rate of same substance were also different. Isopulegol performed significant attractive effect on females in the flow rate of 150 m L/min and concentration of10?L/m L; Nonanal had significant repellent effect on female at the flow rate of 100 m L/min and the concentration of 10?L/m L, while showed some attractive effect on male under the flow rate of 200 m L/min, concentration of 0.1 and 1 ?L/m L.4. EAG was also used to test the responses of P. striolata against the host plant compounds. It was found that dimethyl phthalate, dibutyl phthalate and diisobutyl phthalate caused electroantennogram responses. These 3 substances were further tested for the olfactory response of P. striolata adults. The results showed that dimethyl phthalate and dibutyl phthalate had significant attractive effect in specific concentration and flow rate,and the reactions of male and female to the same concentration and flow rate of same substance were also different. While diisobutyl phthalate did not cause any attractive or repellency reaction of P. striolata.5. The effective compounds from body and host volatiles were mixed and the attractive effect of the mixtures were detected. The results showed that the mixture of dimethyl phthalate with isopulegol and the mixture of dimethyl phthalate with dibutyl phthalate had significantly attractive effect in specific concentration and flow rate, and the reactions of male and female to the same concentration and flow rate of same substancewere also different. While other two mixtures(isopulegol with dibutyl phthalate and isopulegol, dibutyl phthalate with diisobutyl phthalate) did not cause any attractive or repellency reaction of P. striolata.6. The effective substances and their mixtures which had been determined in the laboratory were finally tested in the field. Results showed that different material had different effect on P. striolata. The mixture of isopulegol, dimethyl phthalate and dibutyl phthalate had significant attractive effect compared with control. The attraction effect of this mixture was better than its single compounds.