| Joint actions for mixtures of abamectin and insecticides in cotton bollworm, Helicoverpa armigera and other agricultural insect pests were evaluated by bioassays, and relationship of synergistic effects of the mixtures to synergists, cuticular penetration, metabolic enzymes, and a target enzyme was studied by synergistic bioassays, isotope tracing tests, and biochemical tests. Besides, a foliar residue test and a susceptibility baseline were set up for insect growth regulators (IGR) in H. armigera, and cross resistance to pyrethroids was assayed.1. At first, bio-activities of abamectin and synergistic effects of abamectin mixed with other insecticides were assessed. Results showed that abamectin had high insecticidal activities to H. armigera, Myzus persicae, Plutella xylostella, Pieris rapae, Chilo suppressalis, Bemisia tabaci, Lirimyza sativae, Panonychus citri, Tetranychus urticae, T. cinnabarinus with 1.134×10-4 to 3.460×10-2ug/larva of LD50 or 1.450×10-3 to 1.117×μg/ml of LC50. Among joint actions of abamectin mixed with 13 insecticides in 7 insect pests, petroleum spray oil (PSO) and hexaflumuron were highly synergistic to abamectin in H. armigera with 420.0 and 253.3 of co-toxicity coeffeciency (CTC) respectively. A strong synergism was also found in the mixture of fenvalerate and phoxim in the pest with 330.6 of CTC. There were synergistic actions for abamectin mixed with fenpropathrin, alpha-cypermethrin, cyhalothrin, or esfenvalerate in P. xylostella, L. sativae, M. persicae, or P. citri with CTC 133.8 to 386.5, or mixed with chlorpyrifos or phoxim in H. armigera and P. xylostella with CTC 151.1 to 194.5. And abamectin mixed with azocyclotin or imidacloprid was synergistic or additive in P. citri and B. tabaci with 98.3 to 229.3. However, the mixtures of abamectin and monocrotophos, diazinon, or methamidophos had additive or even antagonistic effects in C. suppressalis and H. armigera with CTC 34.1 to 144.6.2. Also, synergisms of IGR in H. armigera and P. xyllostella were assayed, their poisoning symptom and mode of action was observed, and a foliar residue test for IGR in the 1st instar larvae of H. armigera and its susceptibility baseline were established, then cross resistance of hexaflumuron was studied. After treated withhexaflumuron, RH5349 and tebufenozide, larvae of 2 insect pests tended to move slowly with little sensitivity to a stimulate, feed on few food, molt abnornally and eventually die. Larvae treated with hexaflumuron died with a special symptom of the thin integument and a white transparent prominence on head, while larvae treated with RH5349 died with black and shrunken bodies, and living larvae abnormally molted in advance. Hexaflumuron had high contact and stomach toxicities to H. armigera with 0.7434 μg/larva of LD50 or 2.0592 mg/L of LC50. Tebufenozide was also stomach poisoning with 25.2576 mg/L of LC50, but RH5849 had little contact poison with more than 39.3633 μg/larva of LD50. PBO had a dose-dependent effect on hexaflumuron toxicity in H. armigera, i. e. synergistic at low dosages, but antagonistic at high dosage. A significant synergism was found in the mixture of tebufenozide and PSO in P. xyllostella, or the mixture of tebufenozide and hexaflumuron in H. armigera. When treated with RH5849 mixed hexaflumuron, some larvae of H. armigera showed the poisoned symptom of hexaflumuron, others were the symptom of RH5849, whereas a few larvae had the mixed symptom. Compared with topical application, IRAC No.7, and diet incorporation test, foliar residue test with 1 st instar larvae was a quick, easy, reliable technique and mostly suitable for IGR bioassay and resistance monitoring in Helicoverpa and Heliothis. There was no cross resistance to hexaflumuron in 2 fenvalerate-resistant field strains of//, armigera.3. Then, influences of petroleum spray oil (PSO) and synergists on toxicities of abamectin in H. armigera were studied. PSO and PBO increased the toxicity of abamectin in larvae, but the mortalities were not affected by DEF and TTP. The synergistic action of PSO was more si...
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