How to prevent diseases of sweet potato during storage

Fresh sweet potato is safely stored over the winter, and the sale in the wrong season brings higher economic benefits to potato farmers. in the sweet potato producing areas in the suburbs of Beijing, it has become fashionable to store sweet potatoes.

The fresh potato has the advantages of large volume, high water content, tender tissue, thin skin, easy to be damaged, susceptible to chilling injury and infection. Sweet potato is warm and afraid of cold and dampness. during storage, sweet potato diseases mainly include black spot, soft rot, nematode disease, wet damage, dry damage and so on. The main causes of the disease: potato pieces and potato abduction bacteria, old cellar infection and potato pieces frozen, water stains, broken wounds and so on. The control of environmental factors such as temperature, humidity and air during storage is directly related to the preservation quality of potato cubes. Poor treatment causes the occurrence of the above sweet potato diseases and brings great economic losses to the storers.

I. Sweet potato diseases

1) Wet damage and dry damage of sweet potato. The wet damage is mainly caused by the accumulation of water in the field for a long time, or the rise of water vapor in the potato pile, or the soaking of wet potatoes in the cellar due to rain and snow. The main cause of dry damage is that the relative humidity in the cellar is too low, resulting in physiological atrophy and rot. The lack of oxygen of sweet potato is mainly due to the high temperature at the initial stage of entering the cellar, or overfilling the sweet potato, or sealing the cellar too early will cause the cellar to rot.

2) soft rot of sweet potato. Potato chips mainly occur in the storage period, improper storage will lead to the rapid spread of the disease. After the onset of the disease, the external symptoms were not obvious, only the potato became soft and water-stained, and soon luxuriant woolly mycelium grew on the surface of the potato, with small black particles, that is, the sporangium of the pathogen. After breaking the skin, there is a yellow juice, with a wine flavor, if invaded by backward bacteria, it will become moldy and stinky, and then dry and shrink into a lump.

3) black spot. There are plaster-like green-black spots on the diseased potato pieces, and deep into the potato meat, the taste is bitter. When the spot is wet, the gray mildew layer appears at first, and then there is a black thorn. Diseased potatoes are too bad to eat. The storage period is a period of serious harm and great loss of black spot, and the bacterial source mainly comes from the diseased potato lumps in the field, and the pathogen invades the potato lumps through the wound caused by transportation. at the initial stage of storage, high temperature and humidity can promote the development of the disease, and the pathogen develops rapidly above 15 degrees Celsius.

4) sweet potato nematode. The symptoms of diseased potato can be divided into bran heart type and split skin type: (1) bran heart type. The disease was carried by potato seedlings and seed potato, and the nematode invaded the tuber root from the crutch, and gradually developed from the top of the tuber to the lower part or all around. At first, the longitudinal section of the tuber root showed a cotton-like white bran channel, and later formed a brown chaff channel, commonly known as "bran heart" and "bran flesh". Sometimes although the interior has been destroyed, but the appearance is no different from the healthy, but the weight is reduced. (2) split skin type. The nematode pierced the outer skin with an oral needle and did harm to the inside of the root tuber. the initial symptoms were not easy to see with the naked eye, and the outer skin began to fade, and soon turned green, some with slight depressions, some with small cracks and brown and white dry rot inside. The two types are often mixed.

II. Disease prevention

(1) before storage, sulfur, formalin or carbendazim should be used to sterilize the surrounding and ground of the storage room, and select disease-free, injury-free and insect-free potato pieces for storage.

(2) the volume of potato pieces should not exceed 2/3 of the storage space.

(3) to control the environmental factors such as temperature, humidity, ventilation and ventilation in the storage room. The storage period can be divided into three periods, and the first 20 days are also called "sweating period". Due to the characteristics of high external temperature and physiological activities of potato pieces, they breathe vigorously and emit a lot of water. The management of this period should pay attention to ventilation and dampness, and the middle period of storage is from 20 days to February of the following year, which is also the key period of management. The optimum temperature should be kept at 10 Mel 14 degrees Celsius, and the relative humidity should be 85% RH 90%. When the temperature is above 15 degrees Celsius, it is easy to sprout and reduce the commodity, but if the temperature in the storage room is lower than 9 degrees Celsius for a long time, it is easy to freeze, the inside of the potato becomes brown and black, hard heart occurs, cooking is not rotten, and there is a peculiar smell. and may be invaded by hypothermic bacteria. When the humidity is too high to reach saturation (there are water droplets on the potato pieces), black spot and soft rot are easy to occur; when the humidity is below 80%, the potato pieces begin to lack water, the color of the potato skin is dark, and dry shrinking hearts appear. If the ventilation in the storage room is not good for a long time and the concentration of carbon dioxide increases, the potato will rot. The following March is the late storage period, the external temperature gradually increased, the focus of this period is to pay attention to ventilation and cooling, so that the temperature does not exceed 15 degrees Celsius. Temperature and humidity meters should be placed in different parts of the storage room, observed regularly, and timely and effective management measures should be taken according to different conditions to achieve the purpose of safe storage.