How to prevent and control sesame diseases in hot and humid weather

Recently, some farmers have reported that some sesame plants show leaves curling upward and wilting, some report that sesame leaves wilt rapidly from the top downward, and others report that sesame leaves wither from the bottom upward. What diseases are these exactly? The farmers cannot figure it out either, and they are all asking agricultural technicians for technical guidance, telling them how to prevent and control these diseases.

From the current climate factors, high temperatures accompanied by humidity easily trigger sesame diseases, especially in sesame fields with poor drainage, low-lying terrain, or continuous cropping, which are more susceptible to disease.

From the sesame symptoms reported by farmers in various places, the main ones are bacterial wilt, Phoma stem blight, Fusarium wilt, and Phytophthora blight. Although these four diseases are all whole-plant diseases spread through soil and rainwater, their main symptoms are different. In bacterial wilt, dark green patches appear on the stem at the early stage, then develop into dark brown streaks; the leaves of the diseased plant wilt rapidly from top to bottom, dying as if scalded by hot water. The vascular bundles in the stem turn brown, the pith becomes hollow, and granular bacterial ooze often appears. In Phoma stem blight, the roots first turn brown, then the leaves curl and wilt from bottom to top, the growing point at the top of the plant bends and droops, and then lesions appear at the base of the stem, initially yellowish brown and water-soaked, spreading to the capsules and seeds. In the late stage of the disease, the stem lesions turn brown, and the stem is densely covered with small black dots the size of needle tips. In Fusarium wilt, after flowering, the roots of the plant turn brown, and the leaves wither from bottom to top; the roots and stems are often affected on one side, producing reddish-brown dry streaks, and when humidity is high, pink mold-like growth appears on the lesions. In Phytophthora blight, the main symptom is dry shrinkage and ulceration at the base of the stem, forming a constricted diseased section, initially dark green and water-soaked, and in severe cases the entire plant withers.

Because the above four diseases share some common patterns of occurrence, prevention and control should be approached from two aspects. In terms of agricultural control, in addition to paying attention to selecting good disease-resistant varieties and avoiding continuous cropping, the key is to clean ditches and drain waterlogging. In terms of chemical control, first, spray equal-amount Bordeaux mixture at the early stage of disease onset; second, spray 0.1% copper sulfate solution; third, spray 40% carbendazim or 70% thiophanate-methyl at 500-800 times dilution, continuously 2-3 times; fourth, spray 40% fosetyl-aluminum wettable powder at 300 times dilution 1-2 times. The above measures should be flexibly selected according to local actual conditions.