How to achieve good control of bacterial wilt in black sesame

Black sesame has significant medicinal and health benefits: it can delay aging, nourish the five internal organs, strengthen the bones and muscles, boost energy, tonify the liver and kidneys, and nourish the spleen and lungs. However, bacterial wilt is very common in black sesame production and severely affects its yield and quality. Its disease characteristics and control techniques are as follows:

I. Conditions for occurrence

Bacterial wilt in black sesame is mainly caused by excessive soil moisture in the field. The pathogen overwinters in the soil with diseased plant residues and spreads through flowing water or farming operations. The disease is more severe in continuous cropping fields. The peak incidence often occurs in the hot months of July to August. After a storm, when the temperature rises sharply, the disease is favored to occur and spread.

II. Damage symptoms

Bacterial wilt of black sesame is a bacterial disease. The pathogen invades through root wounds or natural openings and spreads upward from the bottom within the plant's vascular vessels. On affected plants, the exterior of the root and stem shows dark brown streaks, and the internal vascular bundles are brown, with bacterial ooze exuding; after drying, it becomes pitch-black, shiny particles. In the early stage of the disease, the affected plants appear as if lacking water, wilting during the day and recovering at night. After a few days, the leaves wilt rapidly from the top downward, the old leaves droop, and then the whole plant dies. After the leaves are affected, the veins show dark green streaks, sometimes crisscrossing to form a network; when viewed against the light, the center appears oil-soaked. After the capsules are affected, they show water-soaked lesions and gradually turn into dark brown streaks of varying thickness, causing the diseased capsules to shrink, and then the seeds become shriveled and lose their germination ability.

III. Control techniques

(1) Agricultural

1. Select good disease-resistant varieties and carry out a three-year rotation with non-solanaceous and non-leguminous crops.

2. Drainage in the field must be done well. Black sesame is very sensitive to water, so there should be no standing water in the field after the rain stops.

3. Apply more organic fertilizer, especially potassium fertilizer.

4. Promptly pull up and burn diseased plants.

(2) Chemical control

1. Use 1 part lime water and 15 parts lime powder to disinfect diseased planting holes.

2. Before sowing, using chlorothalonil for soil treatment gives good control; or in the early stage of the disease, spray with 50% carbendazim wettable powder at 800-1000 times dilution, or use 50 ml of 3% cresol guaiacol per mu plus 100 g of 50% carbendazim, mixed with 50 kg of water for spraying.