BT insecticides, namely Bacillus thuringiensis microbial insecticides, contain parasporal crystals and spores of toxin-killing insects, which are effective in killing insect pests, and have been widely used for the safety of humans and animals, harmless to natural enemies, and difficult to produce drug resistance. Applied to control crop pests. In practice, the following requirements must be mastered to achieve the best insecticidal effect.
1, master a reasonable application concentration
Different types of pests have different sensitivities to BT insecticides, so the application concentration is different. Only a suitable concentration can be selected based on the sensitivity of pests to achieve good control. Such as rice borer, rice leaf roller, cabbage caterpillar and other sensitive pests, can use 500-1000 times dilution; for the three rice borer, cotton bollworm and other less sensitive pests, you must use 100-200 times the dilution liquid.
2. Apply under suitable climatic conditions. The spores of BT insecticide had the highest activity when the temperature was 20°C-25°C and the relative humidity was more than 85%. The application effect was the best. The activity of the spores was lower than 20°C, prolonged exposure to sunlight, strong storm and other environmental conditions. Low, the application effect is poor, so avoid these adverse weather applications. When the glare and air temperature are above 25°C, it is advisable to apply around 5 pm, and it can be applied on a cloudy day. Spraying the front and back of the blade when applying the medicine can improve the efficacy. The powder should be applied in the morning or evening with dew or light rain to facilitate the adhesion of the agent on the stems and leaves of the crop and to exert its toxic effect.
3, determine the appropriate application time. The efficacy of BT insecticides is slower than that of chemical insecticides. Application time should be 2-3 days ahead of chemical insecticides, and the best effect from egg hatching to 1st instar larvae, such as cabbage caterpillars. In this period of application control effect up to 92%.
4, mixed with chemical pesticides. In order to improve the control effect of pharmaceuticals, especially in the occurrence of pests and the mixture of a variety of pests, they should be mixed with insecticides such as dimehypo, monosultap, triazophos, dichlorvos, and trichlorfon. If only BT emulsion is used with 200 ml per acre, the control effect on rice leaf roller leafworm is only 70%-85%, and the control effect on the rice stem borer is only 60%. If 100ml of BT emulsion per 100ml of 100ml of BT emulsion plus 18% of insecticidal bifida is used, the efficacy of rice leaffolder can reach 95%; 200ml of BT emulsion plus 100ml of double insecticide per acre. The effectiveness of phlegm control can reach 95%. At present, the commercially-available products such as Biling, Green Killing, Special Killing, and Bikilling are all BT powders or emulsions, and the compound preparations of insecticidal single powders or insecticidal two-component fluids should be preferred.
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