Control Methods for Cotton Red Leaf and Stem Blight
Cotton red leaf and stem blight is a physiological disease and one of the main diseases of cotton in the middle and late stages. Over the years, it has occurred severely in sandy loam soil and poor cotton fields in our county. In drought years, especially after a long drought followed by rain or during continuous overcast and rainy weather, red leaf and stem blight breaks out, and cotton plants dry up and die. The damage caused by this disease exceeds the losses caused by other diseases.
Control methods: The occurrence of red leaf and stem blight is closely related to environmental conditions such as soil, fertilizer, water, climate and cultivation systems. Therefore, to control this disease, measures should be taken to apply more organic fertilizer, improve the soil, apply more potassium fertilizer, strengthen field management and prevent fertilizer deficiency in the late stage of cotton. During the flowering and boll stage of cotton, topdressing should be done in time, with attention to applying more potassium fertilizer. In dry years with little rain, for cotton fields without irrigation conditions, wood ash and diluted human excrement and urine can be applied in furrows, 2--3 times in succession, with good disease control results.
In the early stage of the disease, potassium fertilizer can be sprayed on the leaves, and a 1--2% potassium chloride solution (potassium sulfate or potassium nitrate may also be used) or nitrogen fertilizer solution can be sprayed. Wood ash can also be applied as a topdressing at 100 kg per mu each time, with remarkable effects in disease control and yield increase. For drought-stricken cotton fields lacking water, furrows should be opened in time and watering should be done to resist drought, but flood irrigation must be avoided.
After the disease occurs, pesticides can be used in time for control. Method: Use 30 mL of amino acids + 5 mL of propiconazole + 40 g of high-quality potassium dihydrogen phosphate + 30 g of zinc-boron fertilizer, mix with 15 kg of water and spray for control, once every 7 days, spraying 2--3 times in succession, which can effectively control cotton red leaf and stem blight.