Late blight is one of the most common plant diseases. Therefore, it is important to know why the ailment arises, how to identify it, what are the methods for the prevention and treatment of potatoes, effective folk remedies, and also what is a three-time scheme for processing potatoes.
What is late blight and the causes of its occurrence?
Late blight is a common fungal disease of potatoes and other plants caused by mycelial organisms. The vegetable is affected by the fungus phytophthora infestans.
The incubation period of these pathogenic organisms is no more than two weeks, which is why the disease progresses rapidly. Mycelium is found in the tubers of potatoes, which were previously affected by late blight.
The main sources of the disease:
- contaminated soil;
- the remains of diseased plants (tops).
The optimal conditions contributing to the development of the disease are distinguished:
- temperature mode + 15-25 degrees;
- high humidity - more than 75%;
- dense planting.
The pathogen spreads particularly quickly in rainy times, with a sharp change in day and night temperatures, which is accompanied by the appearance of a large amount of dew and fog.
Hot weather is the enemy of the pathogen. The phytophthora spots dry out, the stems are rejuvenated due to the fact that new healthy leaves grow. The fungus at this time spreads extremely slowly.
Signs of potato late blight
The main signs of late blight of potatoes:
- the acquisition of the aerial part of the brown plant;
- twisting and drying of the fleshy part of the leaves;
- the appearance of spots on potato tubers;
- death of the plant, unsuitability of tubers as a food product.
In addition, looking closely at the back of the leaf, you can notice spores of mushrooms that look like white plaque, which will help to accurately determine the disease.
New phytophthora genotype
The causative agent of the disease, which affected potatoes and has long been considered the only genotype, was introduced into European countries in the 19th century. At the end of the XX century, new genotypes of late blight began to be discovered, which were called type A2.
The detection of A2-compatible isolates has become a significant problem, which is associated with greater aggressiveness and virulence of microorganisms. A new fungus could quietly develop under conditions that had a depressing effect on the old form.
The joint development of the local and new populations leads to the appearance of oospores in the affected potato tops. The latter have a thick two-layer shell, which ensures the preservation of viability even in adverse conditions for a long time (about 4 years).
Oospores can withstand low and high ambient temperatures, winter on tubers, the remains of tops, in the soil. It was the appearance of a new genotype that determined a new pathway for the spread of fungi (previously, the soil could not have been infected with pathogenic microorganisms for a long time).
The old form of the disease could affect potatoes only in the second half of the growing season. A new type is able to infect a culture even in the seedling phase.
What is the danger of late blight on potatoes?
Every year in Russia, the loss of potato due to late blight is about 4 million tons. If the disease was detected in the later stages, most likely the plant will die and most of the crop, which will become unsuitable for consumption, will be infected.
In addition, new forms of oospores will remain in the soil, and within 4 years they can cause a new outbreak of the disease if potatoes or other nightshade plants are planted in the same place.
Fungicide potato treatment
The funds of this group are divided into:
- Contact - drugs that protect plants from infection, but are not able to have a direct therapeutic effect. Effective only in the field of their application.
- System - funds that can heal the plant, but only in the early stages of late blight development. The effect persists not only at the place of application, but also inside the plant.
- System contact - combined preparations that can have both preventive and therapeutic effects, penetrating into the plant.
- Translaminar - funds that are able to penetrate into the tissues of plants to a certain depth, but are not carried along the vascular system, which is typical for systemic drugs. A similar effect helps to compensate for the uneven application of fungicide on the surface of the plant.
Pythiaceae family fungi easily develop resistance to fungicides acting inside the plant, and to those that act outside, they are usually always sensitive.
Contact fungicides
Contact fungicides that will effectively fight late blight on potatoes include:
- Antracol - has a versatile effect, is used for late blight and alternariosis on potatoes, washed off by sediments. Process 2-3 times with an interval of 7-10 days. 40 days before harvesting, you should stop processing potatoes with this drug. The consumption of the drug is 2 kg per 1 ha.
- Copper sulfate and Bordeaux liquid(a mixture of blue vitriol in slaked lime). To spray potato tubers before planting, 100 g of the drug is diluted in 10 liters of water. It is more convenient to fold the planting material into a grid for vegetables, and dip the potatoes into the solution.
- Shirlan - An effective prophylactic that has a long period of action of 7 days and is not washed off by precipitation. Usually 2, maximum 4 treatments are required. The first spraying is carried out when the plant reaches a height of about 20 cm, and the next - shortly before the drying of the tops of potatoes begins. The expense of the product is 0.3-0.4 liters per 1 ha of the garden.
Systemic fungicides
Among systemic fungicides, the most effective are:
- Fundazim - a tool with a protective, prophylactic and therapeutic effect. The preparation dryly processes the tubers before planting them at the rate of 20 g of the product per 40 kg of potatoes.
- Quadris - a broad-spectrum fungicide used to suppress the causative agent of the disease when it is just beginning to manifest itself. Six milliliters of suspension are diluted in five liters of water. On one hundred parts of the garden takes 5 liters of the finished solution. The drug does not completely kill the fungus, which may require repeated spraying after a week.
Systemic contact fungicides
This group is represented by the following drugs:
- Ridomil Gold - the most effective and affordable tool in our time. This is a combined fungicide that provides internal (Mefenoxam effect) and external protection (Mancozeb effect). The first spraying is best done prophylactically before closing the tops of potatoes. Then carry out processing every two weeks. There can be three such treatments per season. The solution is prepared as follows: 25 g of the drug are diluted with 10 liters of water. The flow rate of the solution is 20-40 ml per square meter. m landing. Before harvesting, spraying is stopped (2 weeks before this event).
- Metaxil - a drug that has a long prophylactic and therapeutic effect (effective for 2 weeks). This fungicide is characterized by low phytotoxicity. Metaxil is a combined drug, which includes Mancozeb and Metalaxil with contact and systemic effects, respectively. The consumption of the diluted solution is up to 400 l / ha (this is somewhere around 2-2.5 kg of dry product per 1 ha). Usually, they spray up to 3 times per season with a pause of 10-14 days.
Translaminar fungicides
This group can include 2 effective drugs:
- Thanos - also a combined agent that has a therapeutic effect. Thanks to Famoxadone, a film forms on the surface of the leaves of the plant, which acts as a barrier. It is not washed off by rain or water during irrigation. Cimoxanil has an effect on many biochemical reactions that occur inside the fungus, because of which the latter does not develop resistance to the drug. Potatoes are sprayed 4 times (once at each stage of vegetation development): closing of the tops, the appearance of buds, the end of their flowering, the appearance of numerous green berries resembling ovaries of tomatoes. For one spraying, a solution is consumed at the rate of 40 ml per 1 sq. m
- Acrobat - a translaminar fungicide, the active substances of which are dimethomorph and mancozeb. The drug is extremely effective, because the fungus is unstable to it. For one hundredth of the earth, 20 g of the drug are taken, which are dissolved in 5 liters of water. Sprayed a couple of times with an interval of 2 weeks. A month before harvesting, spraying is not recommended.
Safety regulations
When using fungicides, despite the low toxicity of some, protective equipment should be used:
- special clothes;
- gloves
- glasses;
- respirator.
If you are working with Bordeaux liquid or copper sulfate separately, remember that the containers in which the product was prepared should not be used in the future for other purposes. If a solution of one of these fungicides remains unused - dispose of it by burying it outside the territory of the garden or vegetable garden.
The fight against late blight with the help of folk remedies
Among the most common tools used to treat late blight on potatoes, there are:
- Pills "Trichopolum" - dissolve 1 dosage form of the drug in a liter of water and can spray plants with a frequency of 1 time in 2 weeks.
- Wood ash - we can use not only as a preventive, but also a therapeutic agent. As soon as the potatoes rise, sprinkle with aisle aisle. Repeat the action when the plant blooms.
- Milk with iodine - in 10 liters of water we dilute a liter of milk and add 15 drops of iodine. The resulting solution is sprayed with potatoes every 2 weeks.
- Milk serum - an effective tool that can be prepared by diluting serum in water in a ratio of 1 to 1. This tool is absolutely harmless to plants, because of which it can be used with greater frequency - 1 time every 3-4 days.
- Infusion of garlic with potassium permanganate - a solution used to process potatoes. To prepare 10 liters of water, we take 100 g of garlic and 1 g of potassium permanganate. Before preparing the solution, the garlic is ground and poured with a glass of water, after which it is allowed to infuse for 2 days. Filter the resulting infusion, dilute it with water and add potassium permanganate before spraying.
Other drugs and remedies
Among other drugs and agents used in late blight of potatoes, there are:
- Home- a copper-containing preparation that is used as an alternative to Bordeaux liquid to protect potato plantings during the growing season. Available in the form of a green powder, which before use dissolves in water and is sprayed onto plants. The drug "Hom" is processed up to 5 times with an interval of a month. The product is diluted in the following proportions: 20 g of powder in 5 liters of water. The flow rate of the solution will be approximately 7 liters per 100 square meters. m landing.
- Alirin-B – biological fungicide used for prophylactic purposes at any time during growth and before planting or when the first signs of fungal infection occur. The drug is characterized by low risk in relation to humans, plants and the environment. It is produced in the form of tablets, which are dissolved first in a small amount of water (10 pieces in 200 ml), and then this concentrate is poured into 10 liters of water. Also, 1 ml of soap previously presoaked to a liquid state is added to this solution, so that the product sets better and remains on the leaves for a long time. Plants are sprayed with an interval of 10-12 days up to 3 times per season.
Three-time potato processing scheme
As the name implies, in this method, planting is processed 3 times at different periods of plant development:
- From the appearance of seedlings to the closure of tops in the row, Shirlan is used.
- From the closure of the tops to the opening of buds - Ridomil Gold, Metaxil.
- From the appearance of flowers to the dryness of the tops - Acrobat or Thanos.
Prevention methods
The methods of prevention include several methods:
- selection of a place for landing;
- the use of disease-resistant potato varieties;
- special treatment (prophylactic).
We will understand each method in more detail.
Seat selection
It has already been said that contaminated soil in which oospores are located is one of the possible causes of potato damage. It is best to choose a plain for planting.
If the site is in a lowland, then in these places the soil moisture is increased, and therefore the likelihood of developing the disease is high.
Other factors should also be taken into account:
- friability of the soil, good compliance with drainage;
- lack of shading of the site;
- increased distance between plantings of various nightshade crops (to avoid infection of all plants).
Experienced gardeners do not forget that in the same place you can not grow the same crops for more than 5 years in a row.
Especially for potatoes, you can choose good predecessors, which can be:
- perennial herbs;
- winter crops;
- linen;
- beet;
- corn;
- mustard;
- radish.
Subsequently, the crops are mowed and buried in the soil.
Alternating potato plantings every couple of years will significantly reduce the risk of exposure to nightshade phytophthora. Such a system is called a crop rotation. Read more about this here.
Sustainable Potato Varieties
Among the varieties resistant to late blight, note:
- Good luck - characterized by early ripening. Tubers of this variety are large, resistant to many diseases.
- Reserve - medium early potatoes with small eyes. It tolerates drought, great moisture.
- Timo - a high-yielding variety that is not infected with late blight due to its early ripening.
- Nida - mid-season, resistant to late blight and nematodosis, but it is quite whimsical to the growing conditions (it does not tolerate excessive moisture and drought).
- Blue - a potato variety with medium ripening times. It is characterized by high resistance to late blight and low temperatures.
- Lugovsky - mid-season grade. When growing requires systematic hilling. Tubers can be stored for a long time.
- Dawn - An early variety characterized by resistance to late blight, as well as to many viral and bacterial diseases.
- Nevsky - Belongs to medium early potatoes. Often, people prefer the Nevsky variety because of the excellent taste of tubers and a small amount of waste. In addition, these potatoes are well stored.
Treatment
It should be remembered that the use of infected seed guarantees a 100% disease of late blight. But how can we identify tubers affected by a pathogen? To do this, heat the planting potatoes for 2 weeks at a temperature of 16-17 degrees. Maintaining such conditions will allow you to notice the first signs of late blight and discard the affected root crops.
In the fall, when planting material is selected, damaged tubers are burned, not thrown away. In the future, we dry the potatoes and can safely store in a convenient place.
To increase the resistance of the varieties selected by us, we can use fungicides and preparations for processing. Among these funds are:
- Immunocytophate;
- Agat-25K, etc.
Mineral fertilizers are also widely used as prophylactic agents.The amount of potassium and phosphorus substances increases by 2 and 1.5 times, respectively, at the beginning of the development of the culture. Wood ash is a common feeding method used in addition to the above mineral fertilizers.
Care should be taken when applying nitrogenous fertilizers, since they in large quantities cause a delay in the development of the plant's fruits, which makes potatoes more and more susceptible to late blight and other ailments.
Other prevention methods
Often, people contribute to the thickening of the skin of potatoes by loosening the soil and mowing tops. If there is not enough time to carry out these procedures, the Reglon Super preparation is used, which has an identical effect.
Watering plants during drought or low temperatures is carried out only with a hose lowered into the furrows between the beds (sprinkling method is not recommended).
Cultures affected by late blight should be removed and burned as soon as you manage to notice them.
It is also worthwhile to remove weeds in a timely manner, creating favorable conditions for the development of the disease, becoming an ideal storage place for fungal spores or preventing the even application of fungicides to the tops of potatoes.
From this video you will learn what a potato disease such as late blight is, how it develops, and also what are the ways to deal with it:
Despite the fact that late blight is a serious disease, there are many methods and tools to protect potatoes from a pathogenic fungus. The main thing is to closely monitor the culture and adhere to all the rules of prevention.