The bt insecticide, which is a microbial insecticide of Bacillus thuringiensis, is used to kill pests for safety, no harm to natural enemies, resistance to pests, and the like, and has been widely used for the control of crop pests.
In practical applications, due to the fact that some farmer friends do not master the method, the use effect is not satisfactory. The use of bt insecticides has a lot of technical attention and farmers' friends must master it.
Master reasonable application concentrations. Different types of pests have different sensitivity to bt insecticides, so the application concentration is not the same. Only a suitable concentration can be selected based on the sensitivity of pests to achieve good control. Such as rice borers, rice leaf roller, cabbage caterpillar and other sensitive pests, can be used 500 to 1000 times dilution. For pests that are less sensitive to S. indicum, cotton bollworm, etc., 100-200-fold dilutions are used.
Choose to apply under suitable conditions. The spores of the bt insecticide had the highest activity when the temperature was 20-25°C and the relative humidity was more than 85%, and the application effect was the best. Under the conditions of temperature below 20°C, prolonged exposure to sunlight, severe storms and other environmental conditions, the activity is low, and the application effect is poor, so it is necessary to avoid these adverse weather applications. When light intensity and air temperature are above 25°C, it is advisable to apply around 5 pm, and it can be applied on a cloudy day. When spraying, both the underside and the back of the blade should be sprayed thoroughly to improve the efficacy. The powder should be applied in the morning or evening with dew or light rain, so that the agent adheres to the stems and leaves of the crop and exerts its toxic effect.
Determine the appropriate application time. The efficacy of bt insecticides is slower than that of chemical insecticides. Application time should be 2 to 3 days ahead of chemical insecticides, and the best effect is from egg hatching period to 1st instar larval period, as in this case. In one stage, the control effect of cabbage caterpillar was 92%.
Mixed with chemical pesticides. In order to improve the control effect of pesticides, especially in the event of pest occurrence and mixing of various pests, it is advisable to mix pesticides such as dimehypo, monosultap, methamidophos, triazophos, dichlorvos, trichlorfon and other chemical insecticides. . If only bt emulsion is used, 200 ml per mu, the control effect of rice leaf roller leafhopper is only 70% to 80%, and the control effect of the rice stem borer is only 60%. If 100 ml of bt emulsion per acre and 100 ml of 18% of insecticidal double water agent are used, the control effect on rice leaf roller can reach 95%. 200ml of bt emulsion per acre plus 100ml of insecticidal doubles per mu, and the control effect of the two types of warts can reach 95%. At present, the marketed sales of pesticides such as Bilingual, Green Killing, Special Killing, and Bite Killing are all mixed preparations of bt powders or emulsions and insecticidal powders or insecticides, and should be preferred.