Biological Activity Benzothiazole And Trans-2-hexenal Against Bradysia Odoriphaga(Diptera:Sciaridae)at Different Developmental Stages

The sciarid fly Bradysia odoriphaga (Diptera:Sciaridae) is a serious pest of the Chinese chive, Alliumtuberosum Rottle ex Spreng, in China. The larvae gather in the roots and stems of the plant, making them hard to control with common strategies and causing a huge yield loss of Chinese chives. Generally, applying organophosphate insecticides, such as chlorpyrifos and phoxim, are the main methods of pest control for Chinese chives. However, increased public concern over the residual toxicity of organophosphate insecticides and pesticide poisoning from eating Chinese chives has resulted in calls for new and less poisonous approaches to control this pest in recent years. In this paper, we studied the biological activity of volatile compounds of fungus benzothiazole and volatile compounds of plant trans-1-hexenal on different stages of B. odoriphaga, the fumigation activity against adult, eggs, larvae and nymph was studied under the laboratory conditions, and the adults’ respiration rate was tested using oxytherm. Futhermore, the role of these two VOCs in the behavior of adult B. odoriphaga was investigated using electro antennogram (EAG) and behavioral (olfactometer) techniques; the oviposition behavior was observed with the exist of these two VOCs; applying VOCs on yellow sticky card for trapping experiment to test the influence of trapping effect. The main results are as follows:1. Benzothiazole and trans-2-hexenal had good fumigation toxicity on different stages of B. odoriphaga, and benzothiazole has relative good poison activity. The results showed that the LC50values of benzothiazole against female and male adults were0.186-0.052and0.163-0.039μL/L at0.5-2.0h after treatment, respectively. After fumigation with0.01-0.13μL/L benzothiazole for24h, the egg hatching rate of B. odoriphaga at6d after treatment was4.83%-82.39%, while that of the control was96.97%. The LC50value of benzothiazole against the4th-instar larvae at6-72h after treatment was1.247-0.248uL/L. After fumigation with0.01-0.09uL/L benzothiazole for24h, the eclosion rate of pupae was8.17%-69.63%at5d after treatment, and that of the control was96.23%. The results showed that the LC50values of tran.s-2-hexenal against female and male adults were0.243-0.450and0.207-0.415 μL/L at0.5-2.0h after treatment, respectively. After fumigation with0.16-0.36μL/L trans-2-hexenal for24h, the egg hatching rate of B. odoriphaga at6d after treatment was37.82%-93.93%, while that of the control was94.62%. The LC50value of trans-2-hexenal against the4th-instar larvae at6-72h after treatment was6.430-2.077U.L/L. After fumigation with1.00-3.00μL/L trans-2-hexenal for24h, the eclosion rate of pupae was11.20%-84.40%at5d after treatment, and that of the control was97.60%.2. Respiratory rate of female and male adult in2.5h after dealing with the dosage of LC50concentration of each VOCs respectively, the results of these two VOCs were similar with the initial respiratory rate of treatment group was higher than that of control group, then that of treatment group decreased to the even level compared with control group, at last respiratory rate of female and male were lower than the control group significantly.3. The results of EAG experiment showed that both sexes of adult B. odoriphaga showed obvious EAG response to benzothiazole and trans-2-hexenal in0.05-500mu L/mL concentration range. Female adults elicited electroanten-nogram more sensitive response to benzothiazole than that of male adults, while male adults elicited electroantennogram more sensitive response to trans-2-hexenal than that of female adults.4. The role of benzothiazole and trans-2-hexenal in the behavior of this herbivores was investigated using Y-tube olfactometer, benzothiazole had good luring effect on adult at the dose of0.5μL, the luring rates on female and male adults were88.33%and78.33%; while trans-2-hexenal had repellent effect on adult at the dose of10.0μL, as shown by the deterrent rate on male and female adults were96.67%and98.33%respectively.5. These two kinds of VOCs has obvious effect on the oviposition behavior of B. odoriphaga in3,30,300μL, the egg number on the Chinese chive treated by benzothiazole were much higher than control; while the egg number on the Chinese chive treated by trans-2-hexenal were just the reverse.6. The results of applying300μL volatile compounds on yellow sticky card for trapping experiment shows:the sticky card which coated with benzothiazole luring more adults than control, while the result of trans-2-hexenal is just the opposite.