Sweet potato stem nematode disease

Symptoms are also known as delirium, epilepsy, scorpions, palpebral fissures, and the like. It is a devastating disease. The main damage is potato, stem and bacterin. Stems and roots are stunted, short or deformed and severely dead. Seedlings infected with low incidence, dwarf, yellow, longitudinal stem base, see brown voids, cut after the white pulp or very little. The epidermis of the late stage was broken into small cavities, and the pith was brown and dry and rot was cut. No white pulp was cut. Stems of vine vines on the basal part of the stem of vines appear yellow-brown cracks on the upper surface of the abductor, and then become brownish. The pith shows white dry rot. The severe basal vines are short, and the leaves turn yellow or the main vines die. The roots are infected and the dermis or cracking of the epidermis. Root infection caused by different sources of infection, the symptoms of heart-type, split skin type and mixed type 3 kinds. Heart-shaped bacterins, seed potatoes with nematodes, nematodes invaded from the disease abductor into the root tuber, from the top of the root tuber disease, and then gradually expanded to the lower and four weeks, the first was a cotton-like white tunnel, and later turned brown, namely the core , sometimes not visible from the outside, only light weight; split skin type is mainly transmitted by the soil, nematodes penetrated the outer skin of the camp block with a kiss needle, drilled into the interior, the outer skin faded, and later became blue, and some were slightly sunken or raw Small cracks, subcutaneous tissue changes expose the virtual, the final cortex to become dark purple cracks, the interior was brown and white in the rot; hybrid type both the heart and the split skin.

Pathogen Ditylenchus destructor Thorne called potato rot nematode or destructive stem nematode, a parasitic plant nematode. Morphological characteristics can be found in potato stem nematode disease.

Transmission pathways and onset conditions Stem nematodes can multiply year round and continue to be damaged during the whole growth period and storage period of sweet potatoes. When conditions are appropriate, each female produces 1-3 eggs. For a lifetime of 100 to 200 tablets, it takes 20 to 30 days from spawning to hatching. The nematode is active at 2-30°C, and spawns and hatches above 7°C, 25-30°C is the best, endurance to low temperature is strong, it is lethal at 7°C for 25°C, and it is not active at 35°C for the potato. The surface layer of seedlings was soaked in warm water of 48-49°C for 10 minutes. One year live under dry conditions and survived in field soil for 3-5 years, mainly through seed potato, soil, manure, and seedlings. Many nematodes are adult or larvae that live in the soil and invade from the attachment point of the potato block, and move up along the medullary or cortex, causing parasite life. After the yam with stem nematodes was planted in the field, stem nematodes followed the incoming ones, but they mainly stayed inside the potatoes and drilled into the new potato pods. Even if disease-free seedlings are planted, the nematodes in the soil can invade the seedlings 12 hours after planting, and the natural holes or wounds on the epidermis of the end of the seedlings can directly invade from the natural orifice or wound, resulting in cell emptiness. Storks or only the cell wall and fibrous tissue remain, and the tubers are dry and rot-like.

Control methods (1) Quarantine the seed potatoes, and select resistant varieties such as Lushu No. 3, No. 7, Jishu No. 10, No. ll, and Beijing 553. Disease resistant varieties include Lushu No. 5, Jishu No. 2, Jishu No. 5, Ji 73135, Ji 78268, Yan 3, Yanyan 6, Haifa No. 5, and short-grained red heart king sweet potato. (2) Use net fertilizer. After the harvest, remove the diseased body in time to reduce the bacteria source. (3) Do not feed on the diseased potato or its dried potato or diseased quail to prevent stem nematodes from entering the manure through the digestive tract of livestock. (4) Rotation is promoted for rotation with crops such as tobacco, rice, cotton, and sorghum. (5) To establish a disease-free field and choose disease-free seed or high-cut seedlings. Prevent seedlings from carrying nematodes. (6) Adopt formula fertilization technology. (7) Chemical control Every 667m2 with 5% stemline granules l-1.5kg, sprinkled on the stem base of Dioscorea cirrhosa, and then cover the soil with water.