H Series Of The New Bacillus Thuringiensis Pesticides Against The Plant Parasitic Nematodes And The Striped Flea Beetle, Phyllotreta Striolata

In the experiments of the greenhouse and field, the control effects of new Bt preparations against plant parasitic nematodes and flea beetle were studied. Base of the data obtained from the greenhouse experiments and field condition tests, a reasonable and practical method was built which can give the scientific theoretical foundation.According to the growth characteristics of Bacillus thuringiensis and the fermentative production of basic principles, the industrial fermentation mediums and conditions of Bacillus thuringiensis, Bt-A and Bt-B were screened and optimized. After the extensive liquid fermentation production process, the new Bt preparations, DP HA, HB, HD and HF was prepared through handling and processing of fermentation products.The bioassay experiments in the laboratory, the aqueous suspension of Bt preparations at 100 mg/ml concentration has a good activity to Meloidogyne incognita. The death rate is 60% or more, treated after 24 hours.In the greenhouse texts, the tomato roots was inoculated with M. incognita at 1000 second-stage juveniles per plant. The aqueous suspension of Bt preparations, DP HA and DP HB were used to tomato roots and its surrounding soil soon after. The results show that the prevention rate reached over 70%.The tests were carried out under the field conditions using root-knot nematodes, soybean cyst nematodes and flea beetle as the testing insects. The results show that, when DP HA applied 0.5 g m-1 and 1 g m"1, the death rate of root-knot nematodes was over 90% after 9 days. With increasing concentration of DP HB, the death rate increased. When DP HB applied 6 kg ha-1, the death rate reached 40% treated after 7 days. Compared to the untreated control, the Bt agents applied at 75 kg ha-1 and 105 kg ha-1 were effective in reducing the number of cysts of soybean (70%) which quiet equal to FOS,50 days after treatment application. The control effect of DP HD applied at 105 kg ha"1 reached 63.4% before harvesting, and DP HA and HB applied at 105 kg ha"1 also reached 40-50% during the same period. But the control effect of FOS 10% GR only reached 27.6%. This shows that the agents of Bacillus thuringiensis, DP HA, HB and HD can maintain a longer term efficacy.And the Powder HF applied at 15kg ha-1 was also effective against Phllotreta spp. on radish plants (over 60%), both larva and imago. This show that DP HF can control the harm of Phllotreta striolata in effect.The results of greenhouse experiment and field condition tests indicate that the Bt preparations, DP HA, HB and HD are promising microbial pesticides for the biological control of plant parasitic nematodes and DP HF is against flea bettle and have great potential and value in actual agricultural production and application.