| The invasion of alien species has become a serious global environment problem. Hyphantria cunea (Drury) has been ranked as one of the most important alien invasive pests since it occured in Dandong in 1979. It leads to hazard consequences and great loss in recent years. In this study, the high toxicity Bacillus thuringiensis isolates against H. cunea (Drury) was screened among 43 Bt isolates. And the biological and insecticidal characteristic, the cry gene-type and compatible withβ- cypermethrin were also researched in this paper. The results as follows:1. The bioassay result indicated that Bt S-19 isolate was best among 43 isolates. And it was lethal to some Lepidoptera and diptera pests.The LC50 of this isolate against 1st, 2nd, 3rd, 4th,5 th larvae of H. cunea (Drury) was 1.8×105 cells/mL, 2.3×105 cells/mL, 8.1×105 cells/mL, 1.3×106 cells/mL and 3.1×106 cells/mL respectively. The S-19 was lethal to Helicoverpa armigera,Mythimna separate, Spodoptera exigua and Culex pipiens paliens, which LC50 of Bt S-19 against H. armigera , M. separate and C. pipiens paliens was 9.03×106cells/mL, 3.1×107cells/mL and 3.45×104 cells/mL respectively, and the corrected lethal rate against 1st Spodoptera exigua was 94±0.15% in 72h. But it was low activity to Clostera anachoreta , which mortality was 26.8±0.05% against 2nd larvae in 96h.2. The crystal shape of Bt S-19 was rhombus, and the logarithmic growth period was 2-5h . The cry genes, identified in Bt S-19 isolate, was different from other Bt strains to H. cunea (Drury).The gene-types of the Bt S-19 isolate was identified by PCR-RFLP and SDS-PAGE methods. cry1Aa, cry1Ab, cry1Ga, cry1Af, cry2Ab and vip3A genes and 130 kDa, 88 kDa, 70 kDa, 57kDa proteins were identified in this strain respectively.3. The activity ofβ-cypermethrin against H. cunea (Drury) can be enhanced by pretreated with Bt.The LC50 ofβ-cypermethrin against H. cunea (Drury), pretreated with Bt, was 1.2430 mg/L and 0.7625 mg/L, while the LC50 of CK was 4.0751 mg/L, 1.2811 mg/L in 24h and 48h, the CTC was 330, 168 respectively. And the LT50 was shorter 36h than CK at the concentration ofβ-cypermethrin 1.0 mg/L, which pretreated with Bt. When the bioassay was carried out by mixture, the enhancement was prominent at <6 mg /L ofβ-cypermethrin, and with the antagonistic action at >7.5 mg /L.4. The germination of spore and the split of vegetable cells of Bt may restrained by high concentration ofβ-cypermethrin. This was maybe the reason of the antagonistic action of mixture.Detected spore and crystal of Bt in different concentration ofβ-cypermethrin mixture, the shapes had no obvious change at different period of time in different treatment. The logarithm stage of Bt was delayed byβ-cypermethrin, and the more dense ofβ-cypermethrin was, the later of logarithm stage was.The concention of proteins by SDS-PAGE showed the same trend, which the concentration of the proteins was contrary related with the concentration ofβ-cypermethrin. All these results indicated that the germination of spore and the split of vegetable cells of Bt may restrained by high concentration ofβ-cypermethrin.
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