With the long-term heavy use of chemical pesticides in crops, especially in vegetables, the issue of pesticide residues is attracting more and more attention. People are increasingly calling for pollution-free vegetables, eliminating pesticide residues from the source, developing green agriculture, and improving biological pesticides. The control effect has become an inevitable trend. First, the role of bio-pesticides Bio-pesticides are derived from biological (animals, plants, micro-organisms), with specific control effects for specific pests, and highly safe pesticides. Biological pesticides have the advantages of high efficiency, low toxicity, no residue (no accumulation in the environment), and low drug resistance. Biological pesticides mainly have the following three major categories: 1. Bt is Bacillus thuringiensis microbial insecticide, which is a Bacillus, insecticidal active ingredients are parasporal crystals and spores, Bt kills pests is mainly stomach poisoning, After eating, the pests stopped feeding due to the action of bacterial toxins. At the same time, the spores germinated and proliferated in insects, resulting in the death of pests. 2. Abamectin is a new type of antibiotic insecticide acaricide, mainly stomach poisoning and contact toxicity, almost no systemic absorption and fumigation, it can enter the body through the insect's pores and claw pads, while having good The conduction of the cortical flow is to prevent the nervous system from affecting the life of the pests. The insects began to experience paralysis symptoms after taking food, and the subsequent activities and feeding behaviors are delayed until they stop. 3. Nicotine is a botanical insecticide. The main components are nicotine and oxymatrine. They have stomach poisoning, contact and fumigation on pests. The poisoning mechanism on the pests is paralysis nerves. The vapor of the smoked tobacco can penetrate into the body from any part of the body and cause poisoning. effect. Second, determine the appropriate application time Biological pesticides and chemical pesticides, insecticide efficacy generally slow to play, the application time should be appropriately advanced. Taking avermectin insecticide as an example, in the hatching period of pests such as Plutella xylostella, it is best to apply pesticides to the second instar larvae, and the control effect on the older larvae and pupae is low. Bt and nicotine have higher control effects on young larvae than old larvae. Third, according to the object of control, a reasonable grasp of the application concentration. Different species of pests, different insect pests of different insect pests on the degree of sensitivity of biological pesticides are not the same, must be selected according to the sensitivity of pests of different types of pesticides and use concentrations in order to receive good control effect. For example, cabbage caterpillars are more sensitive to avermectin and Bt, which can be controlled by avermectin 3500--4500 times, Bt: 500--1000 times. IV. Choosing the right climatic conditions The biological activity of abamectin is related to 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 various kinds of vegetable pests in hot summer and autumn seasons. The spores in earthworm insecticides have the highest activity when the temperature is 20°C-25°C and the relative humidity is more than 85%, and the application effect is good. However, they are active in the environment where the temperature is below 20°C and prolonged exposure to sunlight and strong storms. Stronger, less effective application. When the light and temperature are above 25°C, it is advisable to apply it around 5 o'clock in the afternoon in order to avoid the destruction of spores by sunlight and ultraviolet rays, and it can be applied on a cloudy day. Fifth, pay attention to spraying methods As biological pesticides are mainly based on stomach poisoning, it is even more important to pay attention to the uniformity of spraying when spraying. Spray the front and back of the leaves to increase the efficacy. To increase the adhesion of avermectin, a small amount of vegetable oil may be added during dilution. Powders and granules of Bt should be applied in the morning and evening with dew and light rain, so as to facilitate the adhesion of pesticides to the stems and leaves of crops. For thicker waxy vegetable varieties, a small amount of washing powder may be added when the pesticide is diluted, which also helps to enhance the adhesive ability of the medicine.
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