Bt insecticide application techniques matter; mastering the method is key
Ethephon is an organophosphorus broad-spectrum low-toxicity plant growth regulator that promotes ripening. It can enter the plant through leaves, bark, fruit, and seeds, then be transported to the sites where it acts, releasing ethylene. It can promote fruit ripening and coloring, promote the abscission of leaves and fruit, dwarf plants, and change the ratio of female to male flowers...
Bt insecticide, namely Bacillus thuringiensis microbial insecticide, has the characteristics of being safe to use for killing pests, causing no harm to natural enemies, and making it difficult for pests to develop resistance. It has already been widely used to control crop pests. In practical application, because some farmer friends have not mastered the method, the use effect is not entirely satisfactory. Using Bt insecticide involves many technical points, and farmer friends need to master them well. Master a reasonable application concentration. Different pest species have different degrees of sensitivity to Bt insecticide, so the application concentration is different. Only by choosing the appropriate concentration according to the pest's sensitivity can a good control effect be achieved. For sensitive pests such as rice skipper, rice leaf roller, and cabbage caterpillar, a 500-1000 times dilution can be used. For less sensitive pests such as yellow stem borer and cotton bollworm, a 100-200 times dilution should be used. Choose to apply under suitable conditions. The spores of Bt insecticide have the highest activity and the best application effect when the temperature is 20-25°C and the relative humidity is above 85%. Under environmental conditions such as temperatures below 20°C, long periods of sunlight, and strong wind and rainstorms, the activity is lower and the application effect is poor, so application should avoid these unfavorable weather conditions. Under strong light and temperatures above 25°C, application at around 5 p.m. is appropriate, and on cloudy days it can be applied all day. When applying the pesticide, spray the underside and back of the leaves thoroughly to improve efficacy. Powder formulations should preferably be applied in the morning and evening when there is dew or after light rain, so that the pesticide adheres to the crop stems and leaves and exerts its toxic killing effect. Determine the appropriate application time. The efficacy of Bt insecticide is slower than that of chemical insecticides, so the application time should be 2-3 days earlier than that of chemical insecticides. Application from the peak egg-hatching stage to the first-instar larval stage gives the best effect. For example, controlling cabbage caterpillar during this period can achieve a control effect of up to 92%. Mix with chemical insecticides. To improve the control effect of the pesticide, especially when pests break out massively and multiple pests occur together, it is advisable to mix it with chemical insecticides such as bisultap, monosultap, methamidophos, triazophos, dichlorvos, and trichlorfon. For example, if Bt emulsion is used alone at 200 ml per mu, the control effect on rice leaf roller is only 70%-80%, and the control effect on striped stem borer is only 60%. If 100 ml of Bt emulsion plus 100 ml of 18% bisultap aqueous solution is used per mu, the control effect on rice leaf roller can reach about 95%. If 200 ml of Bt emulsion plus 100 ml of bisultap is used per mu, the control effect on striped stem borer can reach 95%. Pesticides currently sold on the market such as Bishuangling, Lüshaming, Tesharming, and Bishaming are all compound formulations of Bt powder or emulsion with monosultap powder or bisultap aqueous solution, and should be preferred.