Sweet potato black skin, crack, was originally sweet potato black spot disease at play?
Many farmers who planted sweet potatoes have to be confused by this. They found that their sweet potatoes have black skin and cracks, but they don’t know why. In fact, this is because the sweet potato has black spot disease, the following small series will introduce the sweet potato black spot.
First, sweet potato black spot
1. Causes and symptoms. In the case of sweet potato, black skin actually has black spot disease, and black spot disease is also called sweet potato black spot disease. Sweet potato black spot can occur from the seedling stage, the field growth period and the harvest storage period, directly causing dead seedlings, rotten beds, rotten cockroaches, resulting in serious economic losses. The main causes are continuous cropping, extensive field management and management during storage, which makes the incidence of sweet potato black spot disease more and more serious.
The main symptoms: the diseased bacteria in the potato block penetrated into the lower layer of the potato, so that the hard potato surface appeared hard black skin, and the individual potato meat became black and green bitter. The diseased part is lignified and dry rot, and the diseased potato contains toxic substances (halogen) which are inedible. At the beginning of the disease, the underground part of the young stem of the potato seedling or the base of the stem will produce a fusiform or oblong-shaped black spot, which gradually spreads to the ground to become a longitudinal lesion, and continues to expand to make the base of the stem of the seedling black. Soon after the diseased plants were planted, the leaves turned yellow and the plants were short, and finally the lower part of the diseased plants rotted.
2. Control measures. Sweet potato black spot disease should adopt a comprehensive prevention and prevention method, and strictly control the occurrence and spread of the disease from various aspects such as seedling raising, field management and storage.
(1) The medicinal agent treats the potato seedlings in advance. The base of the potato seedlings (3~5 cm) is soaked with 50% dexamethasone, or 50% methyl thiophanate 500~600 times, or carbendazim 700 times solution for 3~5 minutes. After soaking, the preventive effect is planted. it is good. In the seedling stage, the black spot disease mainly invades the white part near the ground, so it is recommended to adopt high shearing seedlings to reduce the pathogens (generally 4 to 5 cm above the ground).
(2) Strengthen field management to prevent diseases in advance. Before the potato is sprayed with azoxystrobin 800 times solution or 50% carbendazim wettable powder, 75% white fungus 500 times solution for early prevention, spray every 3 to 4 times every 7 to 10 days, alternating medication The control effect is better.
(3) Strengthen management during storage. The storage period is the period in which black spot disease is the most dangerous and the greatest loss. The source of the bacteria mainly comes from the diseased potato pieces in the field, and the wounds invaded by the pathogens invade other potato pieces. The initial stage of storage is not very obvious, and the disease is aggravated when it encounters high temperature, high humidity and poor ventilation. Generally, the pathogens develop faster at temperatures above 15 °C, and the potato pieces below 10 °C are susceptible to freezing. Therefore, the storage temperature is controlled at 10~14 °C, and the relative humidity of the air is 80%~90%, which is the key to safe storage and prevention of black spot disease. If you use a concentrated kiln to store sweet potatoes, you should stop the sensation of sweet potato from the beginning.
Second, the sweet potato crack
1. Reason. Sweet potatoes appear to be a physiological phenomenon when they are harvested.
Mainly due to the following reasons:
(1) Because sweet potato grows too fast due to water and fertilizer and weather during the growth process, causing uneven internal and external causes cracking; uneven water during potato filling, sudden watering after long-term drought causes rapid growth of potato, and epidermal growth The speed is slower than the inside and breaks through the skin. Cracks and cracks occur when the interior develops too fast and the outside develops without catching up. The varieties of large potato stalks generally have a heavy crack.
(2) The soil is too sandy or too sticky, the soil layer is thin, the block cover soil is small, and the temperature and humidity change greatly, especially the drought and high temperature. When the temperature is low and rainy, the crack is prone to occur.
(3) Sometimes the sweet potato crack does not rule out the damage of stem nematodes. Sweet potato stem nematodes are mainly transmitted through seed potatoes and soil. When the potato pieces are damaged, they cause cracks on the surface, and the late pathogens cause cracks.
2. Control measures. Prevention and control of sweet potato cracks should mainly strengthen field water and fertilizer management, deep cultivation and fine soil, and reduce the occurrence of soil pests and diseases. In the deep winter season, deep soil is taken to expose the deep soil to the whole winter, until it is flattened before planting. This method has a certain effect on reducing black spot black spot and crack.
The black spot cracking of sweet potato is very common, which greatly reduces the quality of sweet potato. Therefore, growers must pay attention to it and do a good job in prevention and management.
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