Why potato leaves turn black, dry out, and wilt: methods for combating the disease

A good potato harvest depends on soil conditions, planting material, and weather. Sometimes all of these factors are present, but the harvest is poor or spoils quickly.

Healthy, green and juicy tops are an indicator of the health of the tubers and the key to preserving the harvest.

Description of the causes of blackening of potato tops

Potato tops dry out at the end of the growing season, but sometimes long before this, they begin to wilt, turn black, and the leaves dry out. This can occur during flowering, before the flowers appear, and during the period of active potato growth.

The cause may be disease or pests.

The following factors may cause the disease:

• incorrect choice of planting material: non-regional varieties lose resistance to diseases (hybrid varieties are resistant to diseases);
• Violation of crop rotation: pathogens often remain in the soil and, if crop rotation is incorrect, they affect plants at the beginning of growth or during the ripening period;
• selection of a planting site (near groundwater, clay soil);
• Failure to follow plant care rules: excessive waterlogging causes late blight, and too high a temperature causes diseases caused by fungi.

Potato diseases differ pathogens, causing disease:

1. Bacteria: They are transmitted through contaminated planting material and soil, where they persist for a long time and are resistant to low temperatures. Diseases: rot, black leg.
2. Viruses They cause changes in the structure of the entire above-ground part, and the plant is no longer capable of forming tubers. Diseases: various types of mosaic.
3. Mushrooms Affect tubers and the entire above-ground part, making the infected plant susceptible to other diseases. Diseases include fusarium wilt, early blight, rhizoctonia, late blight, and rhizoctonia.

What diseases cause leaves to turn black?

Let's look at the most common potato diseases, which are characterized by blackening of the tops.

Phytophthora

Late blight, late blight, brown rot – the name of a disease of potatoes and nightshades, caused by the fungus Phytophthora infestans.

Most often, the disease appears after mid-July, when temperature fluctuations occur and excess moisture is observed.

Features of the mushroom:

• rapid reproduction;
• spread by zoospores in the soil, on tubers, in places where crops are stored;
• when watering, it gets into the soil from diseased plants;
• Moisture and heat are conditions for the rapid spread of fungus.

Signs of the disease:

• brown spots with a whitish coating on the lower leaves (fungal spores);
• dark brown stripes on the stems;
• dark spots on tubers.

Later, if no measures are taken, symptoms appear on all leaves, all stems are affected, and the tubers begin to rot.

Preventive measures:

• application of antifungal agents to the soil;
• mulching the soil between bushes;
• soil disinfection with green manure (legumes, mustard, rye);
• selection of planting material (choose varieties resistant to fungal diseases);
• observe crop rotation;
• planting away from nightshades (protection from fungal transmission);
• do not plant too densely (if the distances between bushes are small, ventilation is poor);
• carry out hilling (a layer of soil prevents the spread of fungus);
• inspection of plants and removal of infected ones;
• treatment with anti-phytophthora preparations.

Many people are wary of chemical treatments due to the potential for chemicals to accumulate in the soil and tubers, so home remedies are popular. They should be applied at the first sign of disease.

Recipes for late blight:

1. Garlic infusionInfuse 100g of finely chopped garlic in a bucket of water for 24 hours, then spray the tops once every seven days for a month. Use the infusion fresh.
2. Kefir infusionMix 1 liter of sour kefir with a bucket of water and let sit for 2-3 hours. Spray the bushes with the infusion every seven days until harvest.
3. A solution of potassium permanganate (potassium permanganate), boric acid, and copper sulfateStir 1 teaspoon of each product into 1 liter of boiling water, cool, and combine the resulting three liters with 7 liters of water. Stir. Apply in July and August (with a few weeks between applications).

Sometimes home remedies don't help, and then you have to use chemicals to save the plantings.

Stages of chemical treatment:

• tubers before planting (Fitosporin-M);
• tops 25-30 cm high (copper sulfate, Bordeaux mixture, copper sulfate);
• before flowering (wet weather – Epin, Oxyhumate, Exiol; dry weather – Silkom, Krezacin);
• treatment 1-2 weeks after the previous one (Efal, Ditan-M45);
• after 14 days, treat with strong-acting preparations for infestation of large areas (Oxychom, Ridomil);
• after flowering (Bravo preparation);
• formation and maturation of tubers (Alufit preparation).

Pre-sowing soil cultivation and selection of seed material to prevent the occurrence of disease are more preferable measures than treating the diseased plant.

Alternaria

Alternaria is a disease of potatoes and nightshade crops caused by imperfect fungi.

Features of Alternaria:

• appears before flowering and develops throughout the entire period of growth and maturation;
• varieties with medium ripening periods are more often affected;
• the aboveground part is affected (tubers are infected to a lesser extent);
• fungal spores are carried by raindrops, wind, and insects;
• The fungus overwinters on plant debris.

Alternaria develops under the following conditions:

• low moisture;
• dry weather with high temperatures;
• parasitic infestation of leaves;
• nitrogen and potassium starvation;
• high amount of phosphorus;
• viral infection on tubers.

Signs of Alternaria:

1. Dry, rounded, angular, brown spots up to 3.5 cm in diameter appear on the lower leaves (2-3 weeks before flowering). The spots are located in the center of the leaf and have visible rings.
2. The leaf becomes dry and brittle.
3. A coating with spores appears after 2-3 weeks.
4. Infection of stems occurs in the same way.
5. On diseased tubers there are sunken spots with spores.

Alternaria control:

• spraying with Thanos, Utan, Mancozeb, etc. according to the instructions for the drug;
• begin treatment when signs of disease appear;
• only 4 treatments during the growing period.

Origin and spread Alternaria depends on preventive measures:

1. Removal from the site and destruction of diseased plants.
2. Plowing the soil helps to quickly decompose plant debris on which spores live.
3. Isolate potato and nightshade plantings.
4. Do not grow potatoes in one place for more than three years.
5. Balanced composition of fertilizers.
6. Choose varieties that are resistant to Alternaria.
7. Harvest only ripe tubers without damaging them.
8. Remove infected and damaged tubers before storage.
9. Use Integral, Baktofit, Planriz preparations before planting.

Fusarium

Fusarium (dry rot, fusarium wilt) is a plant disease caused by fungi of the genus Fusarium.

Potato infection most often occurs during the formation and development of tubers. It takes about a month from infection to the appearance of disease symptoms.

Signs of fusarium:

• the plant does not receive enough moisture (the absorption function is impaired) - the upper leaves become colorless and curl along the leaf;
• yellowing and falling of leaves;
• the upper part of the stem turns brown, rots (a cobweb-like coating becomes visible) and dries out;
• The tubers of the infected plant rot during storage (1-2 months after harvesting) and dry out.

Features of fusarium:

• fungi - pathogens live on plant remains, in the soil, on seed material;
• fungi penetrate the plant through the root system, through cracks, mechanical damage and damage left by insect pests;
• the plant's supply of nutrients is disrupted (vessels become clogged).

Prevention of fusarium:

1. Removing weeds from the area.
2. Destruction of potato pests.
3. Mowing the tops before harvesting.
4. Avoid damaging tubers during harvesting.
5. Inspection and drying of tubers (remove infected ones).
6. Ventilation, drying and disinfection of the storage room (solution of 2 kg of bleach and 10 liters of water).
7. Crop rotation.
8. Preparation of planting material: proper germination, disinfection with a solution of copper sulfate (2 g) and potassium permanganate (15 g) in 10 liters of water.
9. Planting potatoes at 8-10°.
10. Fertilizing the soil with nutrient mixtures.
11. Hilling.
12. Treatment with 1% Bordeaux mixture before and during flowering.

Rhizoctonia

Rhizoctonia – a fungal disease of plants, caused by the fungus Rhizoctonia solani Kuehn.

Features of rhizoctonia:

• fungal spores live in the soil for 3-4 years and survive at very low temperatures;
• parasitizes on nightshades, cruciferous plants, pumpkins and many other plants;
• transmitted through soil and rainwater;
• reproduces maximally at 15-17°;
• Infection is possible at all stages of growth;
• prefers poorly fertilized, moist and clayey soils.

Signs of rhizoctonia:

1. The disease can be detected by the presence of small bumps (sclerotia) on the tubers, which resemble dried mud. When they merge, they form a larger, "dirty" spot. Sclerotia are the fungus's dormant form.

2. At temperatures above 5°C and high humidity, sclerotia develop into mycelium, which spreads throughout the tuber, sprouts during germination, and roots. An infected tuber may rot without producing shoots.

3. If an infected plant emerges, it will differ from a healthy one: stunted growth, dark brown spots (black rot) are visible on the tuberous shoots and root collar, the stem is thickened at the base, and the leaves at the top turn purple and curl. The diseased bush droops in dry, warm weather, recovering at night. In drought, infected bushes are the first to die.

4. The mycelium on the tuber grows, this leads to the formation of ulcers filled with rot, and subsequently the tuber turns into dust.

5. The stem becomes covered with a white film at the base in damp weather with moderate temperatures—this is a sign of tuber infection. The film's appearance contains fungal spores. This period is called the reproductive phase.

Prevention of rhizoctonia:

• complete replacement of seed material;
• When planting, select varieties that are resistant to rhizoctonia;
• maintaining crop rotation (plant potatoes in the same area every 3-4 years);
• use green manure on the site;
• previous plantings should not include plants prone to rhizoctonia infection;
• organic fertilizer (120-300 kg per 10 m²);
• add ash (into the holes);
• high-quality germination in a bright room (15-30 days before planting);
• treating potatoes with fungicides before planting;
• carry out planting at temperatures above 8°;
• the holes should not be made very deep (loam – 6-8 cm, sandy loam soils – 8-11 cm, peat soils – 12-14 cm);
• harrow a plot with heavy soils on the fifth or sixth day after planting;
• timely harvesting (mid-September);
• Remove infected tops from the site and do not use them anywhere.

Preventative measures will significantly reduce the risk of fungal infection of garden vegetation and crops, and ensure their safety.

Blackleg

Blackleg – a disease caused by the bacteria Erwinia carotovora (three of its varieties).

Characteristics of bacteria:

• unite into colonies;
• reproduce on all nightshades and cruciferous plants;
• they overwinter only on plant remains;
• reproduce in a humid environment and at temperatures above 2°;
• spread at 2-25°.

Signs of black leg:

• the appearance of brown spots on the stem;
• curling and drying of leaves;
• the shoots at the bottom become soft, and green mucus may appear;
• tubers do not form under diseased bushes;
• the appearance of small brown spots on the tubers and their further growth, rotting of the tuber (pus flows out, infecting everything around);
• The pathogen can be carried by insects (Colorado potato beetle).

Prevention of black leg:

1. Remove diseased plants and tubers from the area.
2. Application of ammonium sulfate to the soil.
3. Inspection and removal of diseased potatoes before storage.
4. Drying tubers.
5. Ventilation, drying and disinfection of the storage room.
6. Covering potatoes with straw or a layer of beets during storage (beets absorb moisture).
7. Sowing green manure crops – rye, oats, legumes (except white mustard) disinfects the soil.
8. Do not plant potatoes after infected cabbage and other cruciferous vegetables.
9. Treatment of the crop with the drug "Maxim".
10. Inspect the seeds before planting, remove infected ones and treat them in a solution of formalin, potassium permanganate or spray with a solution of copper sulfate.
11. On the site, treat the place where the diseased plant grew with Bordeaux mixture or a mixture of ash (1 liter) and copper sulfate (1 tbsp).

Preventive measures are available and can be applied in any farm.

How to keep beet tops green

Keeping the tops healthy and fresh green requires following a few rules:

• varieties must be zoned and resistant to diseases;
• nutritious soil at the planting site (not heavy);
• plowing;
• adding lime to acidic soils;
• use of green manure;
• balanced fertilizer composition (taking into account soil characteristics);
• pre-sowing treatment of tubers;
• inspection of the crop before harvesting for storage;
• planting crops susceptible to the same diseases separately;
• removal of diseased plants.

Following these rules will allow you to see the potato plot green and with healthy plants.

The potato tops have turned black – what should I do?

Early prevention of blackening of potato tops yields good results: the plant suffers no more or only a mild form of the disease, and produces a decent harvest.

Prevention of blackening and wilting of tops

• buy planting materials in specialty stores or from trusted sellers;
• correctly determine the doses of applied fertilizers;
• surveying neighbors about the presence of potato diseases on their plots;
• weed removal;
• mowing the tops 2 weeks before digging up the potatoes;
• do not allow infected tops to come into contact with healthy tops;
• do not cover dug up potatoes with tops (pathogens may get in from the tops);
• Early varieties should be dug up as they ripen.

If the plant does become infected, you should first determine the type of infection in order to prescribe the correct “treatment” and hold events:

• treat tops showing signs of disease with Bordeaux mixture;
• remove blackened parts;
• if the disease spreads further, remove the entire bush;
• if the tubers are already ripe, cut off the diseased tops, dig up the tubers and inspect them;
• Remove diseased bushes from the area, trying to avoid contact with healthy plants.

Reviews

Ivan

I didn't have any late blight in my garden until last year. The harvest was good, but a fifth of it died due to late blight, so I threw it out. In the spring, before planting, I decided to treat the tubers with copper sulfate, and in the summer, I treated the potatoes three times with Infinito. And everything was fine!

Zinaida (Moscow region)

My potatoes and tomatoes had never suffered from late blight, but two years ago, the potato leaves turned black, then the entire plant turned black. I sprayed them with a copper-based solution and boric acid. The tops didn't turn black again, but I wasn't happy with the potatoes: they were small and crooked. In the spring, I changed varieties, afraid to plant the old ones again, and added fertilizer to the soil—all the things I'd collected over the winter (ash, banana, orange, and tangerine peels, eggshells). In the summer, just to be on the safe side, I treated them with Bordeaux mixture and a kefir infusion (recommended by those who'd tried it). The potatoes didn't show any signs of disease, grew healthy, and the harvest was very satisfying, despite a rather cool and rainy summer.