What are the control methods for rice grass smut (false smut) of water bamboo?

Water bamboo, also known as high gourd, wild rice shoot, wild rice hand, water bamboo shoot, high bamboo shoot. It is a perennial herbaceous plant with rhizomes in the grass family, genus Zizania. It is divided into double-crop water bamboo and single-crop water bamboo (or divided into one-harvest water bamboo and two-harvest water bamboo); double-crop water bamboo (two-harvest water bamboo) has higher yield and better quality. The ancients called water bamboo “Zizania”. Before the Tang Dynasty, water bamboo was cultivated as a grain crop; its seeds are called wild rice or carved rice, and it is one of the “six grains” (rice, broomcorn millet, foxtail millet, sorghum, wheat, and Zizania). Later, people discovered that some Zizania plants do not head because they are infected with smut fungus, and the plants show no signs of disease; the stem keeps expanding and gradually forms a spindle-shaped fleshy stem, which is the water bamboo eaten today. In this way, people use the smut fungus to prevent water bamboo from flowering and fruiting, and propagate this diseased, malformed plant as a vegetable. It can be used as medicine. In the world, only China and Vietnam cultivate water bamboo as a vegetable. In Baizhuangzi, Xintai, Shandong, water bamboo is honored as one of the three treasures (the three treasures are water bamboo, spring buds, and wild duck eggs), passed down since ancient times. It mostly grows in the lake areas along the Yangtze River and is suitable for growing in freshwater.

Water bamboo is a warmth-loving plant, with an optimum growth temperature of 10-25°C, and it is not tolerant of cold or of high-temperature drought. In plain areas, double-crop water bamboo is mostly planted; double-crop water bamboo is not strict about day length, has high requirements for water and fertilizer conditions, and temperature is an important factor affecting shoot formation. Water bamboo has a well-developed root system and a high water requirement; it is suitable for clay loam or loam with sufficient water sources, convenient irrigation, deep and soft soil layers, fertile soil, rich organic matter, and strong water- and fertilizer-retention capacity.

Water bamboo has two types: autumn-produced single-crop water bamboo and autumn-summer double-crop water bamboo. Both are propagated by division. In the Yangtze River basin, single-crop water bamboo is divided into clumps and planted from Qingming to Guyu, while summer-autumn double-crop water bamboo can be divided into spring and autumn plantings; spring planting is around Guyu, and autumn planting is around Liqiu.

How to control water bamboo leaf spot (false smut)?

Water bamboo leaf spot (false smut) is one of the main diseases of water bamboo. In recent years, due to the increase in water bamboo cultivation area, the disease has become more and more serious. When the disease occurs severely, the leaves turn yellow and die, causing the plants in the whole field to die prematurely, which greatly affects yield.

Symptoms of water bamboo leaf spot (false smut)

It mainly harms leaves. In the initial stage, dense small brown spots form, which later expand into oval brown lesions, sesame-seed-sized and -shaped, with a few forming streaks; the edges are dark brown, the center is light grayish brown, and the surrounding leaf tissue has a yellow halo. When there are many lesions, they cause a larger necrotic area, causing the leaves to gradually dry up and die.

Occurrence pattern of water bamboo leaf spot (false smut)

Water bamboo leaf spot (false smut) is caused by infection by the fungus Cochliobolus miyabeanus. The pathogen mainly overwinters as mycelium and conidia on old plants or diseased residues. The next year, conidia cause primary infection, and infected parts continuously produce conidia for re-infection. The optimum temperature for pathogen reproduction is 28°C; high humidity favors pathogen formation. The pathogen has strong stress resistance and can survive for many years under dry conditions. The pathogen can spread through airflow or rainwater. Under conditions of high temperature and high humidity, continuous water bamboo cropping, high field density, or zinc deficiency and potassium deficiency, plant growth is weakened, and all of these easily induce the disease.

Control methods for water bamboo leaf spot (false smut)

① Cut stubble in winter to reduce overwintering inoculum. In winter, cut stubble 1.5 cm above the ground and carry it out of the field for centralized burning.

② Crop rotation. Rotate water bamboo with taro and lotus root to reduce pathogen accumulation in the field and reduce disease occurrence.

③ Rational fertilization. Give priority to organic fertilizer; especially in places where the soil is potassium-deficient, more potassium fertilizer should be applied and zinc fertilizer supplemented. Organic fertilizer is generally applied at 2500-4000 kg per mu.

④ Irrigate skillfully and dry the field at the right time. During the high-temperature period from July to August, maintain a water depth of 13-17 cm, and change the water frequently to lower the temperature so as to reduce pest and disease damage. Water bamboo fields should be dried; after each weeding, dry the field until the surface soil cracks, then irrigate again, to improve root activity and enhance plant disease resistance.

⑤ Spray pesticides in time. Apply pesticides in time at the early stage of disease onset. The disease generally begins in late May. You can choose 40% isoprothiolane 800-fold solution, 50% iprodione 700-fold solution, 40% carbendazim? sulfur suspension concentrate 500-fold solution, etc. for spray control. Once every 7-10 days, for 2-3 consecutive applications.