Notes on bt
As a bacterial biological pesticide, Bt is particularly effective in preventing lepidopteran larvae, but the following points should be noted when using it:
1. BT insecticide The spores of the agent are most active when the temperature is 20℃-25℃ and the relative humidity is above 85%, and the application effect is best; the activity is low when the temperature is below 20℃, long-term sunlight exposure, strong wind and rain and other environmental conditions, so application The effect is poor, so application in these unfavorable weather conditions should be avoided. When there is strong light and the temperature is above 25°C, it is appropriate to apply it around 5 pm. It can be applied throughout the day on cloudy days. When applying the pesticide, spray both the front and back of the leaves to increase the efficacy. The powder should be applied in the morning and evening after dew or light rain, so that the agent can adhere to the stems and leaves of crops and exert its poisoning effect.
2. Bt is slower-acting than chemical pesticides and lasts for about 10 days. A small amount of adhesive can be added when spraying, such as adding 0.1% washing powder for better results. If you choose to use No. 6 bacterial powder, HD-1 aqueous agent, etc. to spray pests that occur on ordinary vegetables, you can add a small amount of rice paste as an adhesive to increase the adhesion of the liquid.
3. Do not mix with fungicides (such as carbendazim, thiophanate, etc.) when applying. The sprayer that has sprayed the fungicide should also be rinsed clean, otherwise the fungicide will kill some Bt bacteria, thus affecting the insecticidal effect.
4. Pay attention to insect population density. When the insect population density in the field is high, in order to eliminate the pests as soon as possible, a small amount of pyrethroid pesticides, such as pyrethrin, Xingmianbao, Kungfu, etc., can be added. Generally, add 1 to 2 ml to the sprayer. When there is a large outbreak of pests or when a variety of pests occur together, it should be mixed with chemical pesticides such as dimethoate, dimethoate, methamidophos, triazophos, dichlorvos, and trichlorfon. If BT emulsion alone is used at 200 ml per acre, the control effect against rice leaf roller is only 70%-80%, and the control effect against stem borer is only 60%. If 100 ml of BT emulsion and 100 ml of 18% insecticidal aqueous solution are used per mu, the control effect on rice leaf rollers can reach about 95%; if 200 ml of BT emulsion and 100 ml of insecticidal aqueous solution are used per mu, the control effect on rice leaf rollers will be about 95%. The control effect of borer can reach 95%.
5. Determine the appropriate application time. The efficacy of BT pesticides is slower than that of chemical pesticides. The application time should be 2-3 days earlier than that of chemical pesticides to allow the eggs to hatch. The best application effect is from the peak stage to the 1st instar larvae stage. For example, the control effect of cabbage caterpillar fungus can reach 92% during this period.
6. It is prohibited in mulberry gardens and cannot be mixed with alkaline pesticides.