Prevention and treatment of brown spot disease caused by brown and withered petiole of lotus root robe

Recently, with continuous rainy days and high air humidity, lotus root growers often have the disease of clavulosporium brown spot. The disease is the main disease of lotus root, which slightly affects the production of lotus root, and when serious, the incidence rate can reach more than 80%, which affects the growth of lotus root and leads to a reduction in production.

Brown spot of lotus root

Symptoms: the main damage to lotus root leaves, leaves and petioles will be damaged. At the beginning of the disease, there are small green-brown spots on the leaves, and then expand into dark brown irregular or polygonal disease spots, surrounded by yellowish brown halos, the size is 2-8 mm, and there are concentric wheel patterns on the disease spots, which often merge into patches in the later stage, and the pathogenic parts turn brown and dry; petiole disease is easy to break down.

Etiology: the temperature of lotus root growth period is 20-30 ℃. When it is cloudy and rainy and the humidity is high, the disease is easy to occur. The pathogen overwintered with diseased residual tissues such as dead leaves and petioles. In May-June of the second year, conidia invaded from the natural orifice and wound of the plant to form primary infection, and then produced conidia for re-infection.

Control methods: the diseased leaves are removed and destroyed at any time in the middle and later stage of lotus root growth, but care should be taken not to break the petiole, lest Rain Water or pond water be poured into the petiole vents and cause underground stem rot. Pick diseased leaves before harvesting lotus roots and take them out of the lotus fields to be buried or burned so as to reduce the source of initial infection next year; if possible, it is best to carry out crop rotation for more than 2 years; in disease-free fields, choose 2-3 front-end hypertrophic positive lotus roots as seed lotus roots, because of their rich nutrition, the leaves can reach out to the water as soon as possible to enhance disease resistance. Timely sowing, reasonable close planting, improving ventilation and light transmission conditions, adequate application of rotten organic fertilizer, increasing potassium fertilizer, and shallow irrigation after sowing are beneficial to increase the temperature and make the lotus root sprout earlier.