Contents
Withering of potato tops is a natural process that occurs at harvest time. If the foliage turns yellow before this time, then this indicates a violation of the plant vegetation process.
The reasons why potato tops turn yellow are very diverse. This includes elevated air temperature, lack of nitrogen, phosphorus and other fertilizers. Yellow leaves often indicate the spread of diseases or pests.
Causes of yellowing potato tops
Temperature and humidity
The main reason for the wilting of potato tops before harvesting is a violation of the temperature regime. In drought, potato leaves begin to turn yellow from below, gradually this negative phenomenon spreads to the entire bush.
Constant rains or abundant application of moisture will not correct the situation. Then a crust forms on the surface of the soil, which prevents the flow of air to the root system.
If the temperature reaches 30 degrees, then the plant’s metabolism is disturbed. As a result, the yield of potatoes is reduced.
During the growing season, soil moisture should remain at 70%. In arid regions, plantings necessarily require irrigation. The need for additional moisture increases with the flowering of potatoes.
During the formation of tubers, it is necessary to ensure the supply of oxygen to the soil. To do this, loosening the soil is periodically performed.
Fertilizer shortage
The tops of potatoes turn yellow with insufficient intake of nutrients. Most often, plants are deficient in the following substances;
- Nitrogen. If there is not enough nitrogen in the soil, then the leaves of the potato become pale green, after which they turn yellow and fall off. When nitrogen enters, the plant increases its green mass and forms new tubers. For 10 kg of root crops, up to 50 g of nitrogen-containing substances are required. For top dressing, mineral compounds are used, which are introduced into the soil before planting tubers.
- Phosphorus. Phosphorus fertilizer helps the development of the root system, accelerates the formation of tubers and increases the content of starch in them. With a lack of phosphorus, plants tolerate hot weather worse. As a result, the potato does not grow to the required height, and its leaves turn yellow. Up to 0,9 kg of superphosphate is required per one hundred square meters. It is better to apply fertilizer in the fall, so that easily digestible forms of phosphorus are formed in the spring.
- potassium. Due to potassium, the immunity of plants increases, the taste qualities and the duration of storage of tubers improve. With a lack of potassium, the process of photosynthesis is disrupted, and plants tolerate drought worse. Potassium sulphate is used to fertilize potatoes, which is applied in autumn or spring before planting. The fertilizer rate is 1 kg per hectare.
- iron and manganese. With a lack of iron and manganese, potatoes wilt. Feeding plantings with potassium sulfate will help correct the situation. A bucket of water requires 5 g of fertilizer, after which the bushes are watered under the root. For spraying potatoes, a solution of copper sulphate is prepared (50 g per bucket of water). The procedure is carried out every 5 days.
Development of the disease
Early yellowing of tops is often associated with the development of diseases:
Verticillary wilting
If the leaves of the potato turn yellow and dry, this is a sign of a viral infection. Verticillium wilt spreads at a temperature of 17 to 22 degrees. Dark spots form on the cut of the potato stalk. With the development of the disease, the bush must be removed from the site. To prevent wilting, plantings are treated with a solution of copper oxychloride.
Fuzarioz
If yellowness spreads from the top of the potato, this is a sign of Fusarium. The disease develops at high humidity in a cool climate. In this case, it is impossible to save the plantings, so you need to eliminate the affected plants.
For the prevention of Fusarium, you must follow the rules of crop rotation. Planting material is subjected to treatment for disinfection.
Phytophthora
If the tops turn yellow at the bottom of the bush, this is the first symptom of phytophthora. At the same time, dark spots form along the edges of the leaf plate, gradually spreading to the entire bush.
What to do with the spread of phytophthora? Be sure to treat potatoes with fungicides: copper chloride, Kuproksat, Ditamin.
dry spotting
The disease appears on potato leaves two weeks before flowering. First, rounded brown spots appear on the tops of the potatoes, which gradually grow. Dry spotting is determined by the presence of yellowed tops.
The causative agent of the disease is a fungus. Chemical preparations are used to combat it: Quadris, Oxyhom, Ridomil.
pest attack
Potatoes are susceptible to various pests, under the influence of which the tops turn yellow:
Nematode
The potato nematode lives in the soil and feeds on the juice of the root system of plants. As a result, the stem and leaves of the potato turn yellow. The nematode leads to the death of the crop, which can be up to 80%.
To combat the nematode, fescue, lupins, marigolds, rye, oats or peas are planted next to potatoes. Before planting the tubers, urea is introduced into the soil (1 kg for each hundred square meters).
Colorado beetle
One of the most common garden pests is the Colorado potato beetle. This insect eats the tops of potatoes, which causes them to wilt.
To cope with the Colorado potato beetle allows the use of special preparations: Iskra, Bankol, Commander and others. For processing, you need to make a solution. The procedure is carried out during the growing season of plants before the start of harvest.
Next to potatoes, you can plant calendula, beans, marigolds, and tansy. These plants have a strong odor that repels pests.
To get rid of the Colorado potato beetle, folk methods are used: an infusion is prepared based on dandelion, celandine or garlic.
Conclusion
When yellow leaves appear in potatoes, it is necessary to analyze the conditions in which the plants grow. Be sure to adjust the scheme of irrigation and fertilization. If diseases or pests are detected, plantings are treated with chemicals. For prevention, tubers are treated before planting, and marigolds, calendula and other useful plants are planted next to the plantations.
