Occurrence and Control of Cotton Brown Spot
Both the distribution and host plants in the cotton districts have local students, and it is common in eastern China. Only harm cotton. Stevia Rebaudioside M Stevia Rm,Stevia Rebaudioside M,Stevia Reb-M,Rebaudioside M JINING USP INTERNATIONAL CO.,LTD. , https://www.uspintl.com
Symptoms mainly damage cotton seedlings, and the damaged cotyledons can heal each other into irregular spots after presenting small purple spots. The lesions are tan-brown with purple edges and small black spots (conidia) in the middle; the lesions are easily broken into perforations. When the damage is severe, the cotyledons fall early and cotton seedlings die. The pathogen does not invade the stem and the growing point, and the diseased plant can still draw true leaves. The true leaves were attacked, and small purple spots began to appear. Later, they expanded into yellow-brown to grayish-brown, round-purple round spots. When severe, they could cause fallen leaves.
Onset of pathogenic bacteria in the diseased tissue with conidia overwintering, the second year of dissemination of conidia spread to cotton seedlings damage. After the cotton seedlings have been unearthed, the cotyledon is flat and the first true leaf is barely exposed. It is most vulnerable. It is rainy in spring and low temperature, which makes the growth of cotton seedlings weak and conducive to the spread and infection of germs.
Control methods (1) Remove fallen leaves, burn or deep plowing, deep-swab pressure buried in the soil or implement rotation to reduce the source of the disease. (2) Strengthen the cultivation and management at the seedling stage and improve the disease resistance of cotton plants. (3) After the emergence of cotton, in case of low temperature and rain or combined with cold current forecast, spray 600 times with dexamethasone or thiram, or 1:1:200 Bordeaux mixture.