cotton seedling red rot

Symptoms occurred in all cotton areas in China, the cotton areas of the Yangtze River and Yellow River basins were seriously injured, and the Liaohe River Basin also occurred. The disease can be infected at seedling stage and boll stage. The infected buds in the seedling stage were damaged before they were unearthed, and the buds became reddish brown and rotten. After being unearthed, the roots of the damaged cotton seedlings became magnetic, the lateral roots turned yellow, and then became black and brown and rotted. The infected ducts of young stems turn dark brown, yellow stripes appear at the base of young stems near the ground, then turn brown and rot, young roots and young stems swell, irregular grayish-red spots are produced on the edges of cotyledons and true leaves, and pink mildew layers are produced on them when the humidity is high, that is, the conidia of pathogens. Cotton fields sown early in production may encounter low temperature and rainy weather, and the roots rot seriously, resulting in dead seedlings. The base of the adult stem is infected with ring or local brown scar, the cortex is corroded, and the xylem is yellowish brown. Cotton boll disease.See cotton boll red rot.

The pathogen Fusariummoniliformevar.intermediumNeishetLeggett is called intermediate variety of Fusarium moniliforme, F.semitectumBerk.etRav. It is called F.avenaceum (CordeexFr.) Sacc. It is called Fusarium oat, Fusarium graminearum and other fungi, all of which belong to the subphylum of Fusarium oxysporum. F.moniliformevar.intermedium colonies were fluffy, pink, lavender or rose on PDA medium. The concealed cells coexist in single bottle peduncle or double bottle peduncle. Small conidia unicellular, ovate or narrow melon seed-shaped, serial or pseudocephalous, size 5.3-10.8 × 2.7 × 4 (μ m).

The pathogen overwintered with the disease residue or in the soil, and the conidia and mycelium produced by the pathogen became the source of primary infection in the following year. The source of infection at the beginning of the seedling stage may also be the conidia attached to the cashmere of the seeds and the mycelium latent in the seeds, which invade and harm the buds or seedlings after sowing. The fungus is saprophytic during the cotton growing season. During the boll stage, conidia or mycelium spread to cotton bolls by means of wind, rain, insects and other media, causing rotten bolls from the wound, and the diseased bolls carried bacteria inside and outside the seeds, forming a new infection cycle. The growth activity of red rot pathogen was in the temperature range of 3-37 ℃, and the optimum was 20-24 ℃. High temperature is beneficial to infection. The incubation period is 3-10 days, and its length varies according to environmental conditions. Less sunshine, more rainfall and more rainy days can cause pandemics. The incidence of low temperature and high humidity in seedling stage was more serious. Boll period rainy low temperature, high humidity is also easy to develop. The cotton plant is greedy and overgrown or the cotton boll is damaged by diseases and insect pests, and there are many mechanical wounds, and the pathogen is easy to invade and cause serious disease. During the cotton boll cracking period, the climate was dry and the disease was mild.

Prevention and control methods (1) select healthy and disease-free cotton seeds. (2) pay attention to clean the countryside, remove the germs in time, remove the withered branches, fallen leaves and rotten bolls in the field in time, burn them centrally, and reduce the source of initial infection of the bacteria. (3) sowing at the right time, strengthening the management of seedling stage and adopting the technology of formula fertilization to promote the rapid and healthy growth of cotton seedlings and enhance the disease resistance of cotton seedlings. (4) strengthen the management of cotton field, control diseases and insect pests in boll stage in time, avoid wounds and reduce the chance of pathogen infection. (5) seed treatment. Mix 50% carbendazim wettable powder 1kg per 100kg cotton seed. (6) Prevention and treatment of boll period. First, it is combined with the prevention and treatment of other diseases. Second, timely spray 1 ∶ 1 ∶ 200x Bordeaux solution or 50% methyl thiophanate (methyl thiophanate methyl) wettable powder 1000 times liquid, 50% carbendazim wettable powder 1500 times liquid, 65% carbendazim wettable powder 1500 times liquid, every 66m2 spray 100-125L, once every 7-10 days, spray 2-3 times continuously.