White sesame is prone to bacterial wilt after summer rainstorms: how to prevent and control it

    White sesame bacterial wilt is mainly caused by excessive soil moisture in the field. The pathogen overwinters in the soil with the diseased plant residues of white sesame and spreads through running water and farming operations. In continuously cropped fields, the disease is more severe. The peak incidence occurs in the hot months of July-August. After rainstorms, when the temperature rises abruptly, white sesame bacterial wilt is likely to occur and become epidemic.

Sesame bacterial wilt

    I. Damage symptoms

    White sesame bacterial wilt is a bacterial disease. On the outside of the roots and stems of affected sesame plants, dark brown streaks appear; inside, the vascular bundles turn brown, with bacterial ooze exuding, which after drying becomes black shiny granules. In the early stage of the disease, the affected plants look as if they lack water, wilting during the day and recovering at night. After a few days, the sesame leaves wilt rapidly from the top downward, the old leaves hang down, and then the whole plant dies. After the leaves are affected, the veins show dark green streaks, sometimes crisscrossing to form a network, and when held up to the light, the center appears oily. After the sesame capsules are affected, water-soaked lesions appear, gradually becoming dark brown streaks of varying thickness, causing the diseased capsules to shrink, and further causing the sesame seeds to become shriveled and lose their ability to germinate.

    II. Prevention and control techniques

   (1) Agricultural control

    1. Select disease-resistant improved sesame varieties and carry out a three-year rotation with non-Solanaceae and non-legume crops.

    2. White sesame is not tolerant of waterlogging. During the growing period, if heavy rain or rainstorms occur and water accumulates in the field, it should be drained promptly, so that there is no standing water in the field after the rain stops.

    3. Apply more organic fertilizer, especially potassium fertilizer.

    4. Promptly pull out, destroy, or deeply bury diseased plants.

   (2) Chemical control

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

    2. Before sowing, treat the soil with chlorothalonil for a good preventive effect; or in the early stage of sesame disease onset, spray with a 50% carbendazim wettable powder 800-1000 times solution, or use 50 mL of 3% cresol guaiacol plus 100 g of 50% carbendazim per mu, diluted with 50 kg of water and sprayed.