Effects Of Chlorpyrifos On The Population Of Striped Flea Beetle Phyllotreta Striolata (F.)

At present, chemical treatments play a significant role in the control and management of Phyllotreta striolata. In recently, the trend of higher resistance and lower insecticide efficiency were occurred in control of P. striolata. In this study, we have measured the stimulation effects of Chlorpyrifos to the reproduction and host plants of P. striolata. Also, the killing effect of Chlorpyrifos on natural enemy and the population of P. striolata.were also studied in this study. The results were as follows:The developmental duration of the resistant population is shorter than the sensitive population, developmental duration of 1-3 instars the resistant population is shorter than the sensitive population with 1.21 days lag. The survival rate of the resistant population were higher than the sensitive population,the survival rate of 1 instar resistant population were higher than the sensitive population by 9.55%. From the life table, we can observe that the survival rate at 1-3 instars plays an important factor in population tendency index of P. striolata. Significantly higher survival rate was found in the resistant larva population compared with the sensitive population.The usage of Chlorpyrifos causes the decrease in soluble sugar and chlorophyll contents of Brassica campestris L, which affect the photosynthesis capability and the growth of host plants. Also, the usage of Chlorpyrifos causes the increase in soluble protein content, and causes the decrease in amino acid contents, cystine, methionine, tyrosine contents. In addition, we found that the usage of Chlorpyrifos has the restrain effect on the growth of host plant. Significantly higher restrain effect was found in the plant growth with high concentration of Chlorpyrifos. And phytotoxicity phenomenon was observed in host plant with usage of Chlorpyrifos.Feeding selective experiment showed that the usage treatment of Chlorpyrifos has the restrain effect on P. striolata to B. campestris L , however, the non-selective feeding experiment showed that the usage treatment of Chlorpyrifos has no restrain effect on P. striolata to B. campestris.According to the field investigation, vegetables are seriously damaged by P. striolata and the individual quantity accounts for 86.35% of arthropod individual in vegetable field, which causes lower Community's multiplicity and the uniformity in the vegetable field. Araneae, Ummeliata insecticeps is the major predator and its individual quantity accounts for 51.16% of predator individual in vegetable field. The population of predator has positive effect on P. striolata. And the usage of Chlorpyrifos has little effect to U. insecticeps, which is useful to natural enemy resource in vegetable field. The rational interplanting has the positive effect on the control of P. striolata population, which resulted in decrease in the population of herbivorous pests. Also, rational interplanting leads to the stability in arthropod community of vegetable field and the reasonable proportion between pests and insect natural enemy, which is not easier to cause the eruption of herbivorous pests.