Causes and treatment of anthracnose in cucumbers: the most effective methods for maintaining crop health
If you notice yellow spots on the leaves of cucumbers, sound the alarm. One of the diseases with this symptom is anthracnose of cucumbers. Without timely treatment, it can completely destroy the crop.
Read about the symptoms, causes, treatment and prevention of anthracnose on cucumbers in our article.
What kind of disease is this
Anthracnose of cucumbers (see photo) is a fungal disease that affects the entire bush, for sparing and fruits. Gardeners often call this disease by its middle name – verdigris. The causative agent of anthracnose is a fungal bacterium of the genus Colletotrichum.
Disease found everywhere - both in open and closed ground. Cucumbers growing in a greenhouse are more susceptible to anthracnose. But even in a garden bed, he can easily attack a crop.
The disease haunts cucumber at all stages of its development.. The first symptoms are sometimes noticeable even on seedlings. In addition to cucumbers, tomatoes, raspberries, strawberries, currants, grapes, cherries and other crops are susceptible to anthracnose.
Symptoms of anthracnose
Anthracnose appears on all above-ground plant organs (both young and adults), especially affects fruits. On seedlings, the disease manifests itself in the form of depressed brown spots in the root collar area. Symptoms on mature plants are easier to recognize.
Leaves
First, pale green spots with a diameter of about 3 mm appear, which later merge into large ones - up to 4 cm.Over time, the spots become copper-brown, the leaf turns brown, becomes brittle, dries out in dry weather or rots in high humidity. Holes often form in the affected areas.
Fruit
Depressed oblong spots appear on green plants in the form of ulcers of a light brown color and of different sizes. The mycelium of the fungus penetrates 3-4 mm into the fruit. The cucumbers become bitter and subsequently darken and rot. Such fruits are unsuitable for sale and consumption.
Stem
Covered with weeping elongated depressed spots of brown-yellow color. In the affected areas, the stem becomes thinner and breaks, and the plant dies.
With high humidity, the affected areas of the plant become covered with a pink coating - these are fungal spores. Then black dots appear - sclerotia.
Danger and harm caused
Anthracnose spreads quickly and affects all plant organs. The disease leads to a decrease in the quality and quantity of the crop. If the fungus is allowed to spread, the plants may die. The fruits lose the organic acids and sugar they contain, lose their taste - they become bitter and rot.
The fungus is ubiquitous, but it causes the most severe damage to cucumbers in film greenhouses and open ground. Typically, crop losses from anthracnose range from 6% to 48%, in some years they can reach 55%.
Causes of the disease
Anthracnose is spread by wind, rain and insects. Often its sources are contaminated seeds and plant debris.. The fungus can also persist on the internal surfaces of the greenhouse in which the diseased plant grew.
Also fungal conidia spread from diseased plants to healthy ones during watering or direct contact.Weakened plants located in a film greenhouse or open ground are most susceptible to anthracnose.
The fungus develops in conditions of high humidity (90%) and high temperature (22-27 °C). The soil in which anthracnose develops has a high level of acidity and is deficient in potassium and phosphorus. The fungus lives and develops at temperatures from 4 to 30 °C. But when air humidity is below 60%, the disease does not manifest itself in any way.
About other diseases of cucumbers
Causes and treatment of mosaic on cucumbers
Treatment of cucumbers
To keep the plant alive and harvest a healthy and large harvest from it, Anthracnose cannot be ignored. The sooner you notice the disease and begin to fight it, the less losses it will cost you.
There are different methods for controlling anthracnose on cucumbers.: these include agricultural techniques, folk remedies, and chemicals. The latter, of course, are considered the most effective, but also the most unsafe. But, unfortunately, it will not be possible to cope with anthracnose using agricultural methods alone.
Agrotechnical techniques
Agrotechnical methods more suitable for preventing the disease and preventing its spread for healthy plants. This includes crop rotation, removal of plant residues, disinfection of the greenhouse, etc.
Before planting seedlings Carefully inspect each seedling for symptoms of anthracnose. Remove diseased sprouts immediately.
To prevent the disease from spreading among adult plants, the infected bush should also be carefully removed from the garden bed or greenhouse and burned.
If you notice signs of illness at the earliest stage, its development can be easily stopped by reducing air humidity to 60%. But only to stop, not to cure.
The only effective agricultural technique against anthracnose, capable of destroying the fungus - root watering with 1% Bordeaux mixture. To begin, water the soil around the plant generously with water, and then with a solution (1 liter per bush). It should get to the root and base of the stem. Repeat the treatment once every 2-3 days until the fungus is completely destroyed.
Folk remedies
Folk remedies used to disinfect seeds before planting. Firstly, thermal disinfection of the material is carried out. The seeds are placed in hot (about 60 °C) water for 5-6 hours, and then in cold water for 2-3 minutes.
The second method is sterilization in a solution of potassium permanganate. 1 teaspoon of powder is dissolved in 600 ml of water and cucumber seeds are placed there for 20 minutes. After the procedure, the planting material is washed with water.
The third method is the use of natural fungicides. These include mustard, aloe, alcoholic infusions of medicinal herbs:
- The seeds are placed in a 2% aqueous solution of mustard for 6 hours, in alcoholic tinctures of herbs for 1 hour.
- Aloe leaves are placed in the refrigerator for 5-6 days, then the juice is squeezed out of them, diluted with water 1:1 and the seeds are placed in it for a day.
For reference. Treatment of anthracnose in adult plants with folk remedies is considered ineffective by many gardeners.
But among opponents of chemicals, a method is popular, which is considered less harmful to the crop. First, the infected plant is treated with a 5-7% solution of copper sulfate, after which honey, lime and charcoal are applied to the affected areas of the bush.
Root watering with Bordeaux mixture, which was described above, is also considered harmless.
Chemicals
To combat anthracnose at the earliest stage, when it is in infected seeds, use the TMTD disinfectant. The procedure is carried out 2-5 days before planting, calculating approximately 4.5 g of the drug per 2 kg of seeds.
Also Before planting, the seeds are soaked in a solution "Immunocytophyte" or "Tirama" (TMTD).
Anthracnose in adult cucumbers is treated with fungicides. The most effective of them are:
- "Fitosporin". Powder: 10 g per 5 liters of water; 3 sprays with an interval of 10–15 days. Paste: 4 drops per 200 ml of water. Liquid – 10 drops per 20 ml of water.
- "Previkur". 1.5 ml per 1 liter of water.
- "Abiga-pik". Dissolve 40–50 g in a liter of water, then add water to 10 liters. Treat 3-4 times per season at intervals of 20-30 days.
- "Quadris". 5 ml per 10 liters of water. Up to 3 treatments.
- "Tiovit Jet". 30–80 g per 10 liters of water.
- "Fundazol". Used for watering, spraying or treating seeds. 1 g of the drug per 1 liter of water. No more than 2 sprays per season. Seeds are treated a month before planting.
Important! Please read the instructions carefully. After treating cucumbers with chemicals, the harvest is allowed to be harvested only after 5–30 days (depending on the drug).
Be sure to follow safety precautions when working with chemicals. Carry out the treatment in protective clothing, a respirator, goggles, and gloves. After the procedure, it is advisable to throw away the gloves, wash your eyes, hands, face with soap and rinse your mouth.
Working solutions cannot be stored. Be careful: some preparations repel insects, including bees, so you should not use them during the flowering period of cucumbers.
Useful information about crop pests:
Features of treatment in a greenhouse
Greenhouse plants are most susceptible to anthracnose infection:
- Firstly, greenhouse conditions are more comfortable for the development of fungus: moderately high temperature combined with a high level of humidity.
- Secondly, the fungus often remains on the internal surfaces of the greenhouse, systematically infecting the plants in it. Therefore, be sure to disinfect the greenhouse after harvesting and before the new planting season.
- Thirdly, in a greenhouse the plants are located close to each other, which facilitates and accelerates the spread of the fungus.
The convenience of treating cucumbers in a greenhouse is that you can regulate the humidity level yourself. When you detect the first signs of fungus, reduce this indicator to 60% to stop the development of the disease. Then treat the plants with fungicides according to the scheme.
Outdoor treatment
On the beds in the garden, infection most often occurs through seeds, wind and insects. Contaminated soil and plant debris can also cause anthracnose in cucumbers in open ground.
Of the listed methods For beds, root watering and treatment with 1% Bordeaux mixture are best suited. Spraying with preparations is carried out in the early morning (before 10:00) or in the evening (after 18:00), when the plants do not get sunburn. The weather should be dry and windless.
For a longer lasting effect, check the weather forecast for the coming days. If there is no rain, feel free to spray, then the medicinal solution will not be washed off ahead of time.
Preventive measures
Anthracnose spreads rapidly, so instead of wasting energy on fighting it, it is better to pay more attention to prevention.Check plants regularly for signs of disease. to notice it at an early stage:
- Plant seeds only from healthy plants, buy them from trusted producers. Choose varieties that are resistant to anthracnose.
- Before planting, calibrate the seeds, use disinfectants and fungicides to disinfect the planting material.
- Do not ignore the rules of crop rotation: cucumbers are planted in the same place with an interval of 4 years.
- Dig up diseased plants and burn them. At the end of the season, burn the cucumber tops, dig the soil deeply, and remove all plant debris. In the greenhouse, remove the top 10 cm of soil and add new soil.
- Disinfect the greenhouse after harvesting and before planting.
- Add potassium and phosphorus fertilizers to the soil, feed with organic matter and biological products.
- Disinfect the soil, disinfect garden tools.
- Watch out for moisture that accumulates in film greenhouses. Ventilate the greenhouse. Plant plants at a considerable distance from each other so that the fungus cannot move from one to another.
Useful tips
Galina Kizima, a famous gardener and book author, advises spray the plants in the greenhouse with a solution of potassium permanganate, and then pollinate the leaves with mustard powder or ash.
Use Bordeaux mixture in a ratio of 1 tsp. for 5 liters of water. This is one of the most effective ways to treat anthracnose in open ground cucumbers.
Systematic inspection of plants and removal of leaves with signs of infection (primarily from the lower part of the bushes) will not only stop the development of the disease, but also improve air circulation in the garden bed.
Don't neglect chemicals in the fight against fungus.This is the only effective way to treat anthracnose.
Conclusion
Anthracnose is a common fungal disease among vegetables, especially cucumbers. Due to the large number of ways it spreads, it is almost impossible to protect plants from it. Don’t be lazy to carry out preventive measures, follow the rules of crop rotation, pay special attention to the disinfection of seeds, soil, greenhouses and tools. Don't delay treatment. The sooner you notice symptoms and begin to get rid of anthracnose on cucumbers, the fewer plants and yield you will lose.
Carefully study the instructions for the drugs, follow the precautions and rules of use. Remember that after treatment with chemicals, the crop can be harvested after 5-30 days.