| Diadegma semiclausum is a major larval parasitoid of the diamondback moth (DBM), widely distributed in the north of china. The parasitism of DBM by this parasitoid in the field was usual high, indicating high practical potential in the integrated management of DBM. selective toxicity of 12 insecticides and sublethal effect of abamectin to Diadegama semiclausum were studied, with the purpose of providing guideline for the reasonable use of insecticides and coordinating chemical and biological control of P. xylostella. The main results were as followed:(1)Selective toxicity of 12 insecticides to Plutella xylostella and Diadegma semiclausum.Toxicity of 12 insecticides to Plutella xylostella and its parasitoid Diadegma semiclausum was determined with leaf-dip method and vial residual film method, respectively, and the selective toxicity between P. xylostella and D. semiclausum were compared. The results showed that the order of selective ratio of 12 insecticides to Plutella xylostella and Diadegma semiclausum was lufenuron>chlorantraniliprole>sophocarpidine> abamectin> emamectin benzoate> pinetoram> diafenthiuron> indoxacarb> spinosad> chlorfenapyr> chlorpyrifos>beta-cypermethrin; Lufenuron showed highest positive selectivity to D. semiclausum and P. xylostella with the selective toxicity ratio (STR)> 1141.6, chlorantraniliprole showed higher positive selectivity with STR was 169.2. The four insecticides (sophocarpidine, abamectin, emamectin benzoate, spinetoram) showed moderately positive selectivity, and their STR was 19.8～57.0. Diafenthiuron, oxacarb, spinosad and chlorfenapyr showed low positive selectivity, and their STR was 1.9～6.6. Chlorpyrifos and beta-cypermethrin showed negative selective toxicity to D. semiclausum and P. xylostella, their STR were lowest with 9.0×10-3 and 0.9×10-3, respectively.(2) Bioactivity of 12 insecticides on adults and pupae of diadegma semiclausum. The toxicity of 12 insecticides on adults of diadegma semiclausum was determined by vial residual film method and feeding method, respectively; and on pupae of diadegma semiclausum was determined by impreanation method. The results indicated:chlorfenapyr, chlorpyrifos, beta-cypermethrin and pinetoram showed highest toxicity in adult contact and ingestion experiments, with 100% mortality; Emamectin benzoate, indoxacarb, diafenthiuron, sophocarpidine and spinosad showed higher toxicity, with 50%-99% mortality; Abamectin showed lower toxicity.with 49.2%,45.9% mortality, respectively and Lufenuron showed no effect. Pupal treatment with abamectin, diafenthiuron, pinetoram, emamectin benzoate, indoxacarb, chlorpyrifos, beta-cypermethrin emergence rate was less than 50%. Emergence of adult after 24 h, mortalities were 100%,100% and 31.1% with pinetoram, chlorpyrifos and indoxacarb treatments, while the other group wasps had no died.(3) Effect of sublethal dose of abamectin on parastism capacity and biological characteristics of Diadegma semiclausum.2nd instar larvae of diamondback moth were treated with sublethal dose (LC10, LC25) of abamectin using two methods of experimental treatment. The results indicated that the parasitism capacity of female parasitiod significantly decreased, and cocoon formation and adult emergence of their offspring significantly reduced, too. But there was no significant effect on sex ratio and development duration of their offspring. Pupae of parasitoid were treated with recommended concentration of abamectin and adult of parasitoid was treated with sublethal dose (LC10, LC25) of abamectin. The results showed that when different stages parasitoid were exposed to sublethal dose of abamectin, female parasitoid parasitism, cocoon formation and adult emergence of their offspring significantly reduced, the greater the concentration, the higher impact, but there was no significant effect on sex ratio and development duration of their offspring.(4) Effect of sublethal dose of abamectin on physiological and biochemical of Diadegma semiclausum. Activity of protective and detoxification enzymes of Diadegma semiclausum were studied, after in adult stage treated with sublethal dose of abamectin for 1,12,24,48 h. The results showed:compared to the control, sublethal dose of abamectin could promote the activity of SOD and POD, inhibited the activity of CAT in the beginning and then induced the activity. The activity of detoxifying enzymes (EST, GST, MFOs) were significantly reduced or inhibited by sublethal dose of abamectin treatment. |
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