With the improvement of people's awareness of environmental awareness and health, the problem of pesticide residues has been pushed to the forefront. To eliminate pesticide residues from the source, it is necessary to develop green agriculture. In recent years, biological pesticides have become more and more popular. How to improve the control effect of biological pesticides? The Chinese pesticide net Xiaobian gives you an analysis, as follows:
First, the mechanism of biological pesticides Biological pesticides mainly have the following three categories:
l, Bt is Bacillus thuringiensis microbial insecticide, it is a Bacillus, the insecticidal active ingredients are parasporal crystals and spore toxins. Bt kills pests mainly because of stomach toxicity. After feeding, the pests stop feeding because of bacterial toxins. At the same time, spores germinate and multiply in the insects, leading to the death of pests.
2. Yanshen is a plant insecticide. The main components are nicotine and oxymatrine, which have stomach poisoning, contact and fumigation effects on pests. The mechanism of poisoning the pests is paralyzed nerves. The vapor of the smoke can be invaded from any part of the insect body and poisoned. effect.
3, avermectin is a new type of antibiotic insecticide and acaricide, mainly stomach poisoning and contact killing effect, almost no systemic and fumigation effect, it can enter the human body through the insect's stomata and claw pad, and has good The conduction of the cortical flow is to hinder the nervous system from affecting the life of the pest. After the pests take the medicine, they begin to show paralysis symptoms, and then the activity and feeding behavior are slow until they stop and die.
Second, determine the appropriate time for spraying pesticides. Compared with chemical pesticides, insecticides generally play a slower effect, and the application time should be appropriate. Taking avermectin insecticide as an example, in the hatching period of Plutella xylostella and other pests, the application to the second instar larvae is the best, and the control effect on the older larvae and pupae is lower. Bt and ginseng have higher control effects on young larvae than older larvae.
3. According to the object of prevention and control, reasonably grasp the different types of pests applied, the different pests of the same pest are different in sensitivity to biological insecticides, and different types of pesticides and concentrations must be selected according to the sensitivity of the pests. To a good control effect. For example, Pieris rapae is sensitive to avermectin and Bt, and can be controlled by avermectin 3500-4500 times solution; Bt: 500~1000 times solution.
Fourth, select the suitable climatic conditions <br> biological pesticide avermectin biological activity and temperature. At the same concentration, the higher the temperature, the higher the biological activity and the positive temperature effect. Therefore, avermectin is more suitable for the control of vegetable pests in the hot and hot summer and autumn. The spores in Bt insecticide have the highest activity when the temperature is 20 °C~25 °C, the relative humidity is 85% or more, and the application effect is good, but the activity is better in the environment where the temperature is below 20 °C and the sunlight is exposed for a long time and strong storm. Strong, poor application. In the case of strong light and temperature above 25 °C, in order to avoid the damage of spores by sunlight ultraviolet rays, it is suitable to apply at around 5 pm, and it can be applied throughout the day on cloudy days.
Fifth, pay attention to the spraying method, pay more attention to the application of the drug evenly, spray the front and back of the blade, which can improve the efficacy. Bt powders and granules should be applied after dew and light rain in the morning and evening, in order to facilitate the adhesion of the agent to the stems and leaves of the crop. In order to improve the adhesion of avermectin, the pesticide network recommends adding a little vegetable oil when diluted.
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