Integrated Control Methods and Technical Key Points for Rice Sheath Blight in Wild Rice Stem
Wild rice stem (Zizania latifolia) is a unique aquatic vegetable of our country. Only our country and Vietnam cultivate wild rice stem as a vegetable worldwide. The ancients called wild rice stem “gu”. Before the Tang Dynasty, wild rice stem was cultivated as a grain crop, and its seeds were called gu rice or diaohu, one of the “six grains” (rice, millet, broomcorn millet, sorghum, wheat, gu). Later people discovered that some gu plants, infected by smut fungus, did not produce ears and showed no signs of disease, while their stems kept swelling and gradually formed spindle-shaped fleshy stems - this is the wild rice stem eaten today. In this way, people used the smut fungus to prevent wild rice stem from flowering and fruiting, propagating this diseased, malformed plant as a vegetable. It can also be used as medicine.
Growing Environment of Wild Rice Stem
Wild rice stem is a warmth-loving plant, with an optimum growth temperature of 10-25°C; it is not tolerant of cold or of high-temperature drought. In plain areas, double-cropping wild rice stem is mostly planted; double-cropping wild rice stem has no strict requirements for day length but high requirements for water and fertilizer conditions, and temperature is an important factor affecting stem formation. Wild rice stem has a well-developed root system and a high water requirement, making it suitable for clay loam or loam with abundant water sources, convenient irrigation, deep and soft soil layers, fertile soil, rich organic matter, and strong water- and fertilizer-retention capacity.
Wild rice stem has two types: autumn-produced single-cropping wild rice stem and autumn-summer double-cropping wild rice stem. Both are propagated by division. In the Yangtze River basin, single-cropping wild rice stem is divided and planted from Qingming to Guyu, while summer-autumn double-cropping wild rice stem can be planted in two seasons, spring and autumn: spring planting around Guyu, and autumn planting around Liqiu.
Wild rice stem can be divided into four stages:
1) Germination stage: after the beginning of spring, sprouting begins in March and April, with a minimum temperature above 5°C, and 10-20°C being suitable.
2) Tillering stage: from late April to the end of August, each plant can produce more than 10-20 tillers, with a suitable temperature of 20-30°C.
3) Stem formation stage: double-cropping wild rice stem forms stems once from early to late June, and again from late August to late September. Single-cropping wild rice stem forms stems only from late August to early September, with a suitable temperature of 15-25°C; below 10°C or above 30°C, no stems will form.
4) Growth stagnation and dormancy stage: after stem formation, when the temperature falls below 15°C, tillering and aboveground growth stop; below 5°C the aboveground parts die, and the underground parts overwinter in the soil.
Integrated Control of Rice Sheath Blight in Wild Rice Stem
What is sheath blight?
Sheath blight is a fungal disease caused by infection with Rhizoctonia solani. It is one of the most common major diseases of rice; generally, early rice suffers more than late rice, often causing grains to be unfilled and increasing the rate of empty shells, and in severe cases it can cause plants to lodge and die. It is commonly found in gramineous plants such as rice, wheat, and foxtail millet.
Symptoms of rice sheath blight in wild rice stem:
Rice sheath blight in wild rice stem is a common disease of wild rice stem, and its damage has tended to worsen year by year. It mainly damages leaves and leaf sheaths, forming water-soaked, dark green to yellow-brown cloud-patterned lesions. Under high humidity, sparse light brown mycelium grows on the diseased parts, and later small white sclerotia form that gradually turn yellow-brown.
Occurrence characteristics of rice sheath blight in wild rice stem:
The pathogen belongs to the genus Rhizoctonia in the Deuteromycotina. Disease onset is favored by 25-32°C together with cloudy and rainy days; continuous cropping fields have many sclerotia in the soil, and the disease is severe.
Integrated control methods for rice sheath blight in wild rice stem:
(1) Implement more than 3 years of paddy-upland rotation.
(2) Plant at a reasonable density; in combination with intertillage and other farming operations, promptly remove lower diseased leaves and yellow leaves to improve ventilation and light penetration.
(3) Strengthen fertilizer and water management, apply sufficient base fertilizer, appropriately increase phosphorus and potassium fertilizer, avoid one-sided application of nitrogen fertilizer and long-term deep irrigation, and according to the needs of promoting tillering of wild rice stem plants, controlling ineffective tillering, and promoting stem formation, carry out the water management principle of shallow water in the early stage, sun-drying in the middle stage, and moist conditions in the later stage.
(4) In the early stage of disease onset, promptly spray 5% Tian'an aqueous solution at 400 times dilution, or 50% thiophanate-methyl or 50% carbendazim wettable powder at 700-800 times dilution, 40% wensan wettable powder at 800 times dilution, or 5% jinggangmycin aqueous solution at 50-100 ppm; be careful to spray evenly and sufficiently, spraying 75-100 liters of the prepared solution per mu, once every 10-15 days, for a total of 2-3 sprays.