Principle and control of stem blight of water chestnut

Water chestnut, also known as horseshoe, water chestnut, peony, mackerel, black taro, bodhi chestnut, pear, belongs to Monocotyledon Cyperaceae, perennial perennial herbs, oblate, pointed above, smooth and glossy surface, purplish red or dark brown, growing in the pond, dark green stems on the ground, underground corms can be eaten. People also call it a horseshoe because it is shaped like a horse's hoof. Its appearance is like chestnut, not only in shape, but also similar to chestnut in nature, taste, composition and function, and it is also known as "ground chestnut" because it is borne in the mud. Water chestnut has purple-black skin, white meat, sweet and juicy taste, crisp and delicious, and has the reputation of "underground snow pear". Northerners call it "Jiangnan ginseng". It can be eaten raw as fruit and vegetables as well. It is a popular product in season.

Principle of stem blight of water chestnut

Water chestnut stem blight, commonly known as "water chestnut plague", is a major disease of water chestnut, which mainly occurs in southern planting areas, resulting in plant lodging and death, serious yield reduction and even loss of harvest.

The symptoms are mainly harmful to the stem and leaf sheath, and floral organs can also be damaged.

The primary dark green water-immersed irregular disease spot on the leaf sheath can be expanded to the whole leaf sheath, and there are many black spots on the surface, and finally the diseased part is gray-white. The damage to the stem is mostly caused by the expansion of the disease spot on the leaf sheath, initially in the form of dark green water immersion, generally fusiform, oval or irregular, the diseased tissue is soft and sunken, and there are black twisted stripes on the surface, sometimes in the shape of concentric rims. the disease spots can heal each other to synthesize large dead spots, and when the whole stalk is serious, there are a large number of light gray mildew layers on the surface of the disease spots.

The pathogen CylindrosporiumeleocharidisLentz is called Alternaria of water chestnut, which belongs to semi-known fungi of the genus Alternaria. The hyphae are unseparated, colorless to brown, the conidia disk is slender, the conidiophores are clustered, colorless to light brown, short rod-shaped, unbranched, apically pointed; conidia colorless, linear to crescent.

The characteristic of the disease is that the bacteria overwintered in the disabled body. Conidia are produced under suitable conditions. Through the transmission of wind and rain, the spores sprouted and invaded the host, and the disease produced conidia repeated infection after the disease. Temperature 17-29 ℃, rainfall, fog and re-dew are conducive to the disease, if accompanied by strong wind, it is more conducive to the transmission of spores and the occurrence of the disease is more serious. In addition, too dense planting, poor ventilation and light transmission, early partial application of nitrogen fertilizer, lack of phosphorus and potassium fertilizer, the disease is also serious.

Control methods of stem blight of water chestnut:

(1) selecting disease-resistant varieties according to local conditions. Such as Dahongpao water chestnut (Zhejiang local variety), tail pear (Fujian local variety), Guilin horseshoe (Guangxi Guilin local variety) and so on.

(2) rotation of seriously diseased fields with other crops for 2-3 years.

(3) strengthen cultivation management.

Sowing at the right time, reasonable and close planting to prevent excessive humidity in the field; timely irrigation, avoid flooding irrigation, series irrigation, reasonable fertilization, re-application of base fertilizer and organic fertilizer, less application of chemical fertilizer in the early stage, and proper topdressing of nitrogen and phosphorus and potassium fertilizer after entering the corm stage; diseased plants were uprooted in time in the field, and the diseased residual tissue was removed after harvest to reduce the source of bacteria in the coming year.

(4) Pesticide control.

① corm treatment. Use 25% carbendazim wettable powder 250x solution, or 50% topiramine wettable powder 1000 times solution, soak for 18-24 hours and then set aside.

25% carbendazim wettable powder, 1000 times thiophanate wettable powder or 45% desserium 1000 times can be used to control ② in the early stage of the disease in the field. Spray once every 7-10 days for 2-3 consecutive times.

Commonly used agents carbendazim, thiophanate, Dysenamine.

Water chestnut plague is a disease which loses and dies in a large area in a short period of time after being infected by many kinds of bacteria. It is often the field where water chestnuts were planted last year, and the disease is even more serious this year. The main pathogens causing water chestnut plague are fungal Fusarium wilt and anthracnose. As there are many kinds of bacteria, it is difficult to use one method to control them. From the point of view of comprehensive prevention and control, grasping from the beginning and fastening the ring can have the effect of controlling water chestnut plague. Emphasis should be placed on the following aspects of work:

First, it is strictly forbidden to plant water chestnuts in stacked fields, and the fields that planted water chestnuts last year, especially those where water chestnut plague occurred last year, must not be planted this year.

The second is to strictly control the selection of seeds. Water chestnuts from last year's diseased fields can not be used as seeds. The species of water chestnut must remove the water chestnut with disease spots and scars in advance.

Third, a kind of water chestnut and its seedbed soil must be strictly disinfected. If treated with 0.1% topiramate, most bacteria can be killed.

Fourth, before transplanting water chestnut, the soil in the field was disinfected with dimethazone.

The fifth is to strengthen the observation of the disease during the peak tillering period of water chestnut, and immediately use broad-spectrum pesticides such as Baichongqing for protective control once the focus is found. If anthracnose, blight or rust occurs, it can be controlled with 1000 times of difenoconazole (difenoconazole) aqueous dispersion.