Cotton red leaf blight is prone to outbreak after heavy rain, growers need to be vigilant

Recently, cotton regions have generally experienced heavy to torrential rain, and for cotton that has endured a long drought, red leaf blight is extremely prone to outbreak.

Cotton red leaf blight is a physiological disease. It starts from the main stem growing point or the top of the fruiting branch, and generally develops from top to bottom and from outside to inside. The main stem withers and dies, but the dissected vascular bundles show no discoloration. The root system is thick and short, with few fibrous roots and poor development.

The causes of cotton red leaf blight outbreaks are: first, extensive farming in cotton fields, resulting in poor cotton root development; second, cotton fields with poor drainage; third, excessive application of nitrogen fertilizer, vigorous cotton growth, and a shaded cotton field; fourth, too little organic fertilizer and poor soil fertility. From this it can be seen that when the climate changes abruptly, cotton with a poor cultivation environment and incompletely developed physiological functions is prone to red leaf blight. To prevent and control cotton red leaf blight, the following points should mainly be grasped:

1. Control the top and promote the bottom to enhance stress resistance. First, for cotton with relatively vigorous growth, use the plant growth retardant mepiquat chloride or chlormequat to control vigorous growth. Apply 2-3 grams of mepiquat chloride or 8-12 milliliters of chlormequat per mu mixed with 50 kg of water for spraying, which can effectively promote steady growth; second, for cotton fields with compacted soil, cultivate in time to break the compaction and ventilate, enhancing air permeability; third, for cotton fields in lower-lying areas, pay attention at all times to clearing ditches and furrows to promote cotton roots to grow downward; fourth, for cotton fields using double-film cultivation, immediately remove the plastic film so that cotton roots develop deeper.

2. Increase potassium fertilizer application and improve fertilization efficiency. Potassium deficiency is one of the leading factors inducing cotton red leaf blight. For the two types of cotton fields with potential soil potassium deficiency or low potassium application, increase potassium fertilizer by 10-15 kg per mu. First, it can meet the cotton's need for potassium fertilizer; second, it can adjust the fertilizer ratio structure in the cotton field. Improve the utilization rate of nitrogen fertilizer and phosphate fertilizer.

3. Spray outside the roots to improve the oxygen supply and nutrient absorption environment. For cotton that has already developed red leaf blight, as long as the cotton leaves have not withered and the main stem growing point is still viable, root-outside topdressing can be used to quickly restore reproductive function. First, use 100 milliliters of the humic acid active liquid fertilizer Huimanfeng per mu, mixed with 50 kg of water for spraying, which both quickly supplies fertilizer and improves the soil oxygen supply; second, use 100 grams of chemical fertilizer essence per mu mixed with 50 kg of water for spraying, which can supplement major elements and trace elements; third, spraying the plant growth agent "802" can accelerate cell division and enhance the cotton's self-regulation ability.