Key rice diseases to focus on controlling in Guangdong currently

Bacterial leaf streak, rice blast, sheath blight and bacterial leaf blight are the four major diseases in late rice production in Guangdong, mainly damaging the leaves of plants in the early and middle stages of rice growth. The coastal typhoon-prone rice areas of our province are frequent-occurrence areas of bacterial leaf streak, while hilly and mountainous areas are mainly affected by rice blast and bacterial leaf streak. The occurrence periods, characteristics and control methods of bacterial leaf streak, rice blast and sheath blight are briefly described as follows:

Bacterial leaf streak. Rice bacterial leaf streak has shown a spreading trend in Guangdong in recent years. The disease starts at the seedling stage and breaks out severely at the young panicle differentiation stage. Frequent typhoon rain, flooded rice fields or excessive application of nitrogen fertilizer are the environmental triggers for the disease. The lesions on the leaf surface of diseased plants initially appear as semi-transparent, water-soaked short stripes or long stripes, then turn yellow-brown; bead-like bacterial exudate forms on the lesions, and the dried exudate does not easily fall off. For control in the seedling bed, apply pesticide once each at the three-leaf stage of the seedlings and before transplanting, and flooding of the seedling bed must be prevented. For field control, spray 2-3 times in the early stage of the disease, once every 7 days. Per mu, use 7-100 grams of 25% Yeqingshuang, or 50-70 milliliters of BC Mieshdan, or 30-40 grams of 50% Xiao Junling, diluted in 50 kg of water for spray control.

Rice blast. Rice is prone to this disease in the middle and late tillering stages. Large day-night temperature differences, dew on leaves and cool temperatures are the environmental factors that induce the disease. The leaves of diseased plants initially produce water-soaked brown spots, and susceptible varieties quickly form round or oval brown spots; in severe cases, the lesions are densely distributed and the leaves wither and scorch. To prevent the occurrence of this disease, first, plant disease-resistant varieties; second, do not apply excessive nitrogen fertilizer during the main field period, pay attention to the combination of nitrogen, phosphorus and potassium, irrigate with shallow water after transplanting to promote tillering, and drain by opening ditches in time before the peak tillering stage to promote sturdy and healthy rice plants. The key to controlling leaf blast is at the peak tillering stage; spray high-efficiency fungicide immediately at the early stage of the disease, using per mu 75-100 milliliters of 2% JIASHOUMI, or 50-75 milliliters of 40% Fuji One (isoprothiolane), or 50-70 grams of 20% tricyclazole, diluted in 50 kg of water for spray control; if the disease is severe, spray again after 7-10 days. The key to controlling ear blast is to grasp the breaking stage and the full heading stage.

Sheath blight. This disease can occur throughout the entire growth period of rice, with severe damage from the peak tillering stage to the booting stage. High temperature and high humidity and excessive application of nitrogen fertilizer will promote the occurrence and spread of the disease. The leaf sheaths near the water surface of diseased plants are damaged and form oval or cloud-like gray-green to gray-brown spots; in severe cases, the leaves turn yellow and die. In production, strengthening cultivation management, draining and sun-drying the field at the peak tillering stage, reducing ineffective tillers, and lowering field temperature can reduce the occurrence of this disease. When the incidence rate reaches 20%-30%, use 100 milliliters of 5% jinggangmycin aqueous solution or 30-40 grams of 20% powder, diluted in 50-70 kg of water for spray control.