What is the cause of carrot black rot? How to prevent and cure?

Carrots are one of the nutritious vegetables we often eat, which are especially suitable for children and the elderly. Carrots are planted all over our country. In the process of planting, carrots are vulnerable to black rot, which leads to yield reduction and so on. What is the cause of carrot black rot? How to prevent and cure?

First, what is the cause of carrot black rot?

Carrot black rot behaves differently in different periods. Infection at the carrot seedling stage can lead to the quenching of ununearthed carrot seedlings or seedling seedlings; the old leaves of adult plants are susceptible to disease, which first forms black spots on the petiole, and then extends to the leaf tip, resulting in the death of the whole leaf. When the disease is serious, it extends to the root and crown of the carrot, forming a black rot ring (black crown). Dry black invagination focus will appear after carrot infection during the storage period, and the pathogen spreads rapidly among carrots under warm and humid storage conditions.

The infected soil, diseased remains and seedlings were used as the primary infection sources in the field of the disease. Pathogens can survive in crop residue or soil for more than 8 years as spores, and can be transmitted by transfer, running water or wind of bacterial soil and diseased plants.

Symptoms of carrot black rot

Carrot black rot mainly harms fleshy roots, leaves and stems, forming sunken black spots, which seriously affect commercial and edible properties. Infectious bacteria belong to half-known subphylum fungi. Overwintering on the soil surface with diseased remains through hyphae and conidia.

Third, how to prevent and cure carrot black rot?

Selecting rotation plots, avoiding continuous cropping, cleaning up disease residues in the field, soil sterilization, selecting disease-resistant varieties and seed coating sterilization are effective ways to control carrot black rot. The occurrence of black rot in carrot leaves during the growth period not only causes yield loss, but also accumulates sufficient pathogens for fleshy root disease during storage, but also provides access to infect carrot root and crown. Therefore, chemical control in the early stage of leaf disease is an important means to control the disease.

Before storage, wash and remove injured carrots so that the damage degree of carrots can be reduced to a minimum, which can reduce the incidence of carrot black rot during storage. Keeping proper temperature (about 0 ℃) and humidity (less than 92%) during storage can prevent carrots from being infected and reduce the spread of diseases. Sanitary conditions for post-harvest storage are very important for disease control.

To control carrot black rot, the protective fungicide 40% chlorothalonil suspension 200 ml per mu can be used in the early or early stage of the disease, sprayed once every 7-10 days, and used continuously for 3-4 times, which can achieve the control effect of low input and high output.

Dimethimide fungicide isocarbamide has a good control effect on carrot black rot. 500g / L isobaric urea suspension can be used in the early or early stage of carrot black rot, sprayed once in 7 days and 4 times in a row.