Incidence regularity and control of onion neck rot

First, the symptoms mostly occur in the mature period or storage period of onion bulbs. In addition to onions, it can also infect other onion and garlic vegetables. During the growth period, the disease mainly appeared in the neck of the leaf sheath and bulb, the internal tissue rotted, and there was a gray mildew layer when it was wet. During storage, there was a dry and slightly sunken spot on the top of the bulb and shoulder, which became soft and light brown, and there was a gray mold layer between the scales. There are small black-brown sclerotia in the later stage.

The pathogen of the disease belongs to Botrytis cinerea. The pathogen overwintered with mycelium and sclerotia in the field with diseased plant residues or in storage with onion bulbs. The conidia spread with the airflow and invaded from the plant wound. The condition of low temperature and high humidity is beneficial to the disease. It is easy to suffer from rain during harvest, the epidermis of bulbs is not dry and the humidity of storage area is easy to occur. Third, control methods: ① selects disease-resistant varieties and rotates with other vegetable varieties; ② topdressing timely to avoid excessive and late fertilization, and the organic fertilizer put in must go through maturity and not apply more nitrogen fertilizer; ③ scientific watering. Do not flood when watering, pay attention to drainage after rain; ④ when onions are fully ripe, carefully cut the top of the newly harvested bulbs, dry them fully before storage; when ⑤ bulbs are just harvested, irradiate them with infrared light for 6 minutes (the lamp is about 15 cm away from the onions) to reduce decay during storage. ⑥ medicament control can be sprayed during the growth period with 50% carbendazim wettable powder 600x solution, or 40% carbendazim gel suspension solution, or 70% methyl topiramate wettable powder solution 1000 times, generally spraying once every 7 days and 4 times in a row.