The best use of BT insecticide

BT insecticide, namely Bacillus thuringiensis microbial insecticide, contains parasporal crystals and spore toxins that kill pests. It is safe to people and animals, has no harm to natural enemies, and is difficult to produce drug resistance. It has been widely used to control crop pests. However, in practical application, due to the lack of methods, the effect is not satisfactory. In order to improve the control effect of BT insecticides, the following requirements must be mastered: the reasonable application concentration of insect pests is different, the sensitivity to BT insecticides is different, so the application concentration is different. Only by selecting the appropriate concentration according to the sensitivity of pests can a good control effect be obtained. For sensitive pests such as rice bract, rice leaf roller, cabbage worm, etc., one thousand times dilution should be used, while for pests that are not sensitive to Chilo suppressalis and cotton bollworm, a dilution of 100ml and 200 times should be used. The spore of BT insecticide has the highest activity and the best application effect when the temperature is 20 ℃-25 ℃ and the relative humidity is more than 85%. Under the environmental conditions such as temperature below 20 ℃, long-time sunlight, strong wind and torrential rain, the activity is low, and the application effect is poor, so it is necessary to avoid these adverse weather conditions. When the strong light and temperature are above 25 ℃, it is appropriate to apply it at about 5 o'clock in the afternoon, and it can be applied all day in cloudy days. When spraying, the front and back of the leaves should be sprayed through to improve the efficacy. Powder should be applied after dew or light rain in the morning and evening, so as to facilitate the drug to adhere to the stems and leaves of crops and play a toxic role. To determine the appropriate application time, the effect of BT insecticide is slower than that of chemical insecticide, and the application time should be 3 days earlier than that of chemical insecticide, and the effect is the best from egg incubation period to 1st instar larva stage. For example, the control effect of Pieris rapae can reach 92% during this period. In order to improve the control effect of chemical insecticides, especially in the occurrence of major pests and mixed occurrence of many kinds of pests, it should be mixed with dimethophos, monosulfan, methamidophos, triazophos, dichlorvos, trichlorfon and other chemical pesticides. If 200ml / mu of BT emulsion is used alone, the control effect on rice leaf roller and rice stem borer is only 70%, 80% and 60%, respectively. If 100ml of BT emulsion and 100ml of 18% insecticidal double water agent were used per mu, the control effect on rice leaf roller could reach 95%, and the control effect of BT emulsion 200ml plus Shachongshuang 100ml per mu could reach 95%. At present, the pesticides sold in the market, such as Bishuangling, green borer killing, special killing borer, must kill borer and so on, are all BT powder or emulsion, and should be given priority to be used in combination with insecticidal single powder or insecticidal double water agent.