Latest Control Measures for Rice Leaf Tip Blight During Cultivation
Rice leaf tip blight is also known as rice leaf tip white blight. It mainly damages leaves. The disease begins at the leaf tip or leaf margin, then spreads downward along the leaf margin or from the middle, forming stripe-shaped lesions. The lesions are initially dark green, gradually turning grayish-brown, and finally withered white. At the boundary between diseased and healthy tissue there are brown streaks, and the diseased part tends to split longitudinally and break apart. In severe cases it can cause the leaves to wither and die. When it damages the grain, lesions with dark brown edges and grayish-brown centers form on the glumes, and the affected grains are shriveled and light.
Pathogen
Phoma oryzicola, a fungus of the subphylum Deuteromycotina. The pycnidia are initially embedded beneath the rice leaf epidermis, later slightly exposed, dark brown. The conidiogenous cells are single-celled, unbranched, with holoblastic phialidic conidiogenesis. The conidia are ovoid, single-celled, colorless, and contain 1-2 oil globules. The sexual state is Mycosphaerella oryzae, a fungus of the subphylum Ascomycotina.
Transmission Routes and Disease Conditions
The pathogen overwinters as pycnidia in diseased leaves and diseased glumes. The pathogen has more than 10 species of gramineous weeds as hosts, so carrier weeds can also transmit it. The overwintering pycnidia release conidia under suitable conditions, which spread by wind and rain to rice leaves and invade through wounds on the leaf blade, leaf margin, or center of the leaf. Obvious disease centers form from the jointing to booting stage, and a second disease peak appears at the early grain-filling stage. During this period, low temperatures, frequent rain, and frequent typhoons favor disease development. After storms, a large number of wounds are created on rice leaves, making severe outbreaks likely. Excessive or late nitrogen application leads to severe disease, while increased silicon fertilizer application reduces disease severity. If the field is not drained in time at the late tillering stage and water accumulates, the disease is severe. High field density leads to severe disease. The optimal temperature for disease development is 25-28°C; the temperature range for mycelial growth is 10-35°C, with an optimum of 22-25°C; the temperature range for conidial formation is 15-30°C, with an optimum of 25°C; the temperature range for spore germination is 10-35°C, with an optimum of 30°C.
Control Methods
1. Strengthen seed quarantine to prevent introduction into disease-free areas.
2. Select disease-resistant varieties. Japonica rice is more resistant than indica rice. Tall varieties and varieties with long, drooping leaves are more susceptible. Among indica rice, Yangdao 3 and 4, 3037, Nannong 3005, and Xingxian 1 are relatively resistant.
3. Apply sufficient organic fertilizer and increase phosphorus, potassium, and silicon fertilizers. Drain the field at the appropriate time and to an appropriate degree during the tillering stage, and keep the field alternately wet and dry in the later growth period. Do not plant too densely, and reduce field humidity.
4. Chemical control. For seed treatment, soaking seeds in 50% carbendazim or 50% thiophanate-methyl wettable powder at 250-500 times dilution for 24-48 hours, or in 40% Hekuling wettable ultra-fine powder at 250 times dilution for 24 hours, gives good results. From the booting to heading and flowering stage of rice, after discovering central diseased plants, choose 40 ml of 40% carbendazim suspension concentrate or 60-75 g of 40% Hekuling wettable powder, and spray with 60 L of water per 667 sq m. 40% Hekuling can also simultaneously control fungal diseases such as rice false smut, cloud-shaped disease, sheath rot, and purple stem disease.