What to Do About Potato Rot During Storage? Causes and Preventive Measures

Potato is one of the main crops in Qinghai Province, with the characteristics of high and stable yield, a short growth period, and strong adaptability. In addition, it is rich in nutrients, serves as both grain and vegetable, and has high economic value, making it very popular among the general public. In recent years, with the development of the potato industry, significant production benefits have prompted the potato planting area to expand year by year. However, due to extensive scientific management during potato production, harvest, handling, and storage, a large number of seed potatoes rot during storage. According to surveys in recent years, potatoes in most high mountain areas of Qinghai Province have suffered from varying degrees of rot during storage, with severe cases involving whole-cellar rot, causing undue economic losses to farmers and dampening the enthusiasm of farmers to grow potatoes.

I. Causes of Rot During Potato Storage

1. Field infection with late blight is one of the main inducing causes of massive rot during potato storage. At present, the potato varieties cultivated in Qinghai Province, such as Plateau No. 4 and Xiazhai 65, do not have strong resistance to late blight. In addition, in the past two years, continuous autumn rain, insufficient sunlight, insufficient heat, and excessive field humidity have caused potatoes in some areas to be mildly infected with late blight in the field. At harvest, tuber symptoms are not obvious, and farmers do not pay enough attention, putting diseased potatoes directly into the cellar.

2. During harvest and handling, careful lifting, placing, and transporting were not carried out, causing extensive tuber damage. Damaged tubers were not removed before storage, and once placed in the cellar, this provided favorable conditions for pathogen invasion.

3. At harvest, field humidity was high, and tubers had a large amount of soil attached. Before storage, they were put directly into the cellar without drying or ventilation.

4. After potatoes were placed in the cellar, the temperature and humidity inside the cellar were not well controlled. In addition, the stored potato quantity was too large, deteriorating the microclimate inside the cellar, creating conditions for the occurrence of late blight and dry rot, and leading to massive potato rot.

II. Preventive and Control Measures

1. Select virus-free, disease-resistant seed potatoes. Choose locally high-yielding varieties with resistance to late blight, such as Qingcai No. 2 and Virus-free 175.

2. Timely control potato late blight. When central diseased plants are found in the field, remove them promptly. In the early stage of disease onset, you may use 64% Sandofan wettable powder at 500 times dilution, or 58% metalaxyl-mancozeb wettable powder at 500 times dilution, or 65% zineb wettable powder at 500 times dilution, or 25% ridomil wettable powder at 1000 times dilution for spraying. Spray again after an interval of 7-10 days, for 2-3 consecutive sprays.

3. Do a good job of pre-storage handling:

① Before storage, first remove 3 cm of old soil from inside the cellar, dry it in the sun for more than one week, and disinfect with 1% potassium permanganate solution or limewater.

② During potato handling, they must be lifted and placed gently, and never poured directly in from the cellar opening.

③ Before tubers are placed in the cellar, first dry them in a dry, ventilated, dark place for a few days, strictly discard diseased, rotten, and damaged potatoes, and remove attached soil.

4. Do a good job of storage-period management:

① To keep the cellar temperature and the internal temperature of the potato pile consistent, the storage quantity must account for one-half of the cellar capacity. The height of the potato pile should be below one meter, and ventilation holes made of wheat straw or rapeseed straw should be tied and placed upright in the potato pile. The ventilation holes should be about 30 cm higher than the potato pile.

② In the early storage period, open the cellar door and ventilation holes. When the temperature drops to -1°C, block the ventilation holes.

③ Control the humidity inside the cellar. If water droplets form on the upper layer of the potato pile, water droplets appear on the cellar walls, and the potato tubers are damp, this indicates that the humidity inside the cellar is too high, and ventilation should be carried out through the cellar door and ventilation holes.

④ In spring, as the temperature rises, open the ventilation holes or cellar door to keep the cellar door temperature at 1-4°C.