Symptomatic prevention and treatment of dead cotton trees

In recent years, in some old cotton areas, the problem of "dead trees" of cotton has become more and more serious, causing many cotton farmers to suffer losses. Although prevention and control has also been carried out, it is still as serious as a year, and the effect is not ideal. Therefore, it is necessary to "give priority to disease prevention and treatment as a supplement" to prevent and control cotton diseases and reduce the incidence of cotton.

1 for the control of oomycetes diseases

In recent years, the promotion of disease-resistant and insect-resistant cotton species has changed the diseases of "dead plants" of cotton, of which the most important disease is oomycetes, and 60% to 70% are caused by egg fungi such as Phytophthora or Pythium. Although the diseases caused by Fusarium oxysporum and Fusarium oxysporum are still occurring and serious, they are not as harmful as oomycetes. Therefore, cotton "dead trees" should be prevented and treated at seedling stage, mainly by irrigating or drenching roots, and choose fungicides with good ovicidal effect, such as oxazolidone (Yikuangjing), Bingsen zinc (Antaisheng), rooting strong bacteria type 2116, or Yingtian No. 2, and so on.

2 aiming at the prevention and control of diseases

The types of cotton diseases have changed, harming the roots and stems of cotton, causing "dead trees" such as wilt, yellow wilt, standing blight, quenching, blight, basal rot, stem rot, root disease and so on, which can be divided into oomycetes, fungi and bacteria. different diseases need different control methods, and appropriate control measures should be treated differently and taken, including comprehensive medication. If cotton Fusarium wilt occurs in a large area and does great harm, it will be too late to be treated after finding pieces of dead trees. It is best to be in the early stage of the disease, generally before the wheat harvest, in mid-May, the cotton trees are red and green and have not disappeared; at noon, the high temperature and drought is high, but the cotton field is not dry, and individual cotton plants wilt, which seems to be like drought. At this time, the first medication begins, or even ahead of time. The disease could be eliminated by using the medicine to control Verticillium wilt once every 10 days for 3 to 5 days. If the disease has occurred, medication can only play a role in controlling re-development when it has caused a piece of dead trees.

(3) for the prevention and control of soil-borne diseases

Physiological diseases and root diseases are the most obvious in the plots where cotton has been cultivated continuously for many years. The main kinds of soil-borne diseases are Fusarium wilt and root rot. It starts from the root and infects to stems, leaves, bolls and other parts through vascular bundles. In the affected cotton field, a lot of cotton will die from the seedling stage, even if the seedlings are made up, some plants will wilt at the boll stage, and some plants will die. Therefore, the cotton field should be disinfected before planting. Before sowing, apply special soil purifying agent for cotton evenly on the surface of the sowing belt and mix it manually (artificial sowing) or with the seeder. Before sowing or when sowing, 10~12cm under the sowing ditch, or 8~12cm from the side of the sowing ditch, apply special soil purifying agent for cotton. The soil purifier should keep a certain distance from the cotton seeds and should not be in direct contact with the seeds to avoid drug damage. Due to the wide distribution of soil-borne diseases, it is necessary to cooperate with reasonable crop rotation, deep sun exposure and high temperature disinfection in order to eliminate them completely.

4 aiming at the prevention and control of climatic conditions

The occurrence of cotton disease has a certain regularity, and it is most likely to occur in low temperature in spring, high temperature in summer, high soil moisture after rain and watering. It was rainy and cold for more than 10 days, and the temperature of 18-25 ℃ was the best temperature range for the development and spread of Verticillium wilt. A large number of bacteria multiplied and blocked the vascular bundles of cotton plants, affecting the transport of water and nutrients, so leaves wilted or even fell off. After each heavy rainfall in summer, there will be a peak of Verticillium wilt.

There are several peak periods of high temperature in summer every year, when the cotton plant occurs in the peak period of high temperature, and the coming trend is fierce, and the prevention and control is also difficult. Such as improper prevention and control can cause a large area of dead trees, resulting in a great reduction in production, or even no production. In case of high temperature, fungicides should be sprayed and nutritious drugs should be sprayed for prevention. Continuous use of the drugs for 2 or 3 times can effectively prevent cotton disease.

5 change the planting method

Most cotton areas (especially in the northern cotton area) do not have the habit of raising seedlings, but adopt the method of direct seeding, because cotton sowing time is from late April to early May, often encounter "late spring cold" or "overcast and rainy" weather, so that a number of root diseases dominated by Phytophthora and Pythium occur about one month after sowing. Therefore, the planting method of seedling transplanting should be adopted, and the bottom application of bio-organic fertilizer or seed dressing with bio-bacterial fertilizer should be adopted to promote root development and reduce the occurrence of harmful bacteria in the rhizosphere.

(6) to control the "dead trees" of cotton as soon as possible.

Too late or no control of ① is the main reason for the "dead trees" of cotton, which should be controlled at the fixed seedling stage. ② attaches importance to the transmission of germs through ways such as Rain Water and ploughing, and prevents them. Rational application of chemical fertilizers (such as diammonium phosphate, compound fertilizers) and more fully mature organic fertilizers. Pay attention to the characteristics of fungus biological fertilizer against Fusarium wilt and Verticillium wilt. Cotton "dead trees" must be prevented early, especially plastic film cotton, oomycetes occur early, the root system is shallow, and the disease is serious. In the control measures, we should take the application of bio-organic fertilizer, formula fertilization, timely early prevention of diseases, reduce the loss to the minimum, timely uncover the film in cultivation measures, and cooperate with topdressing, soil watering and so on.