Methods of dealing with late blight on potatoes
Phytophthora is a dangerous fungal disease that can destroy almost the entire planting of potatoes and nightshade plants. Less commonly, buckwheat, strawberries and other agricultural crops are affected. In past centuries, this pathogen even became the cause of hunger. Phytophthora on potatoes appears as dark spots and white bloom covering the tops. The tubers begin to rot in the ground. There are many methods of fighting the fungus and preventing infection, but it has not yet been possible to defeat the disease until the end.
Methods of dealing with late blight on potatoes
Causes of late blight
Oomycetes from the genus Phytophthora cause late blight on potatoes. Unlike fungi, their cell wall is not chitin, but cellulose. Physiologically, they are closer to plants than to fungi, therefore phytophthora, which causes plant diseases, has been placed in a separate taxonomic group.
The microorganism parasitizes on nightshades (potatoes, tomatoes, eggplants), but it can also infect other plants. Propagated by zoospores that are stable in the external environment. Phytophthora winters calmly in the ground, even in severe frosts. Zoospores are well preserved on the soil surface, in last year's tops, tubers and even on bags or dirty tools, therefore they are advised to be disinfected after harvesting.
In spring, when the temperature rises above 10 ° C, zoospores germinate. This is facilitated by the high humidity in the region of 75-90%. No wonder late blight is detected on potatoes especially often in rainy years. Phytophthora often appears on potatoes planted in a swampy field and in a lowland.
Infection occurs in different ways. If you use diseased planting material, the fungus will spread first to the roots, and then to the stem and leaves, young tubers are affected instantly. The same is the mechanism of the spread of the disease when the soil is contaminated. Phytophthora is airborne and infects potatoes. Then the spores are washed away by the rain, they fall into the ground and infect the lower part of the plant. If the disease is detected in time and the plant is treated, the tubers will remain healthy.
Signs of late blight
According to the description, the incubation period of potato late blight lasts 3-16 days. At first, the disease goes unnoticed, especially with the primary defeat of the tubers, then brown spots appear on the tops. On the lower part of the leaves, a white bloom is noticeable, which looks like a thin cobweb. This is the mycelium of the fungus. After the first symptoms appear, the disease progresses rapidly. The tops wither and dry out for several days.
If you dig up tubers from the soil under an infected bush, you will notice brown spots that unevenly cover the surface of the potato. The section shows how the mushroom penetrates deep into the tuber, brown paths go from the surface to the center, then the potato begins to rot. By the time of harvest, there may be nothing left under the bushes.
Affected tubers also deteriorate during storage.Within a few weeks, the entire stock turns into a rotten mass.
Prevention of late blight
A disease such as late blight of potatoes is difficult to treat, therefore the main way to fight is to prevent the disease. Particular attention is paid to planting material. You can not plant tubers with spots, signs of rot.
To reveal the latent disease, the tubers are heated before planting at a temperature of 15-18 ° C for 1-2 weeks. On the affected tubers, brown-purple spots or rot immediately appear. Before planting, it is advisable to treat them with fungicides. For example, copper sulfate, immunocytophyte or agate-25. Good results are obtained by germination before planting in a cool room.
Protection of potatoes from late blight is impossible without proper soil preparation. You can not plant a crop after tomatoes, eggplants, buckwheat: the soil may be contaminated. These plants should also not grow near a potato field. If late blight starts on tomatoes, it will spread to potatoes. In one place, it is not recommended to grow potatoes more than 2-3 times in a row. The culture grows well after legumes, oats, mustard. Grass is buried in the fall, and not mowed or taken out of the field. It becomes an excellent fertilizer, and mustard prevents late blight on potatoes.
Planting should not be too dense, then the disease is more slowly transmitted from bush to bush. It is advisable to choose a site in an open, elevated place, well-ventilated and sunlit. It is imperative during the summer to carry out hilling, weeding weeds: then the potatoes are less sick.
Before harvesting, the tops are mowed and carried away from the field, in no case being added to them. The crop is harvested as early as possible before the rains begin. To protect from decay, the crop is dried before being stored in the basement for 2-3 weeks.
After harvesting the field, the soil is thoroughly cleaned of tops and remaining tubers.
Phytophthora develops on potatoes if fertilized with too much nitrogen. From this, the tops grow magnificently, and the tubers develop poorly. Potash and phosphate fertilizers, on the contrary, prevent disease. It is an excellent fungicide.
Means for prevention
All plants must be processed
To prevent disease, you can use effective remedies for late blight on potatoes. They use industrial chemistry, folk methods.
Prevention of late blight on potatoes is carried out with the following fungicides:
- copper sulfate (2 g per bucket);
- Bordeaux liquid;
- "Artsdil";
- Ridomil RC;
- Oxyhom;
- Fitosporin;
- milk whey or reverse;
- iodine.
It is advisable to treat all planting material with preparations, and then spray the first shoots. The third treatment begins in June, when the plant develops most intensively. When the summer is wet, the plant is sprayed with special agents again at the end of July, after flowering. After flowering, it is best to use the following preparations:
- Ditamin M-45 (30 g / l);
- copper oxychloride (60 g / 15 l);
- "Kuproksat" (40 g / 15 l).
The processing of tops and leaves against the fungus is carried out twice with a break of one week. Growth stimulants give a good effect. Here are their dosages per 15 liters of water:
- Oxygumat - 150 ml;
- Exil - 5 ml;
- "Epin" or "Epin plus" - 3 ml;
- Ecosil VE - 5 ml.
It is better to treat plants with stimulants at the beginning of the growing season. Such measures strengthen the plants, after which it is easier to deal with late blight.
Use of resistant varieties
For many decades, breeders have been trying to develop late blight-resistant varieties. Unfortunately, there are no potatoes that are completely insensitive to the disease. But there are varieties that are less often and to a lesser extent affected by the fungus. Here is some of them:
- Rosara;
- Spring;
- Lazarus;
- Nevsky;
- Arina;
- September;
- Sante;
- Mavka;
- Verb;
- Visa;
- Light;
- Tomich;
- Blue.
When choosing resistant varieties, it is important to pay attention to whether they are suitable for the climatic zone, what their yield, ripening time. Early potatoes are affected by late blight less often than late ones.
Late blight treatment
The disease needs to start to heal on time
What if the disease could not be prevented? Is it possible to save the potatoes? The fight against late blight on potatoes will bring good results if the disease is detected in time. It is necessary to treat potatoes in the first days, since the fungus spreads quickly. Then no measures to combat it will help.
Pharmacy products
There are effective drugs for late blight of potatoes in any pharmacy. The antifungal drug "Trichopol" helps to fight the pathogen well. One tablet of medicine is diluted in a liter of water, after which the bushes are sprayed. The procedure is repeated a week later.
Helps to prevent and cure the disease of home potatoes late blight ordinary iodine. To do this, take an alcohol solution and drip 10-25 drops per 1 liter of water. Bushes are processed 2-3 times with a frequency of 5-7 days. To increase efficiency, iodine is not dissolved in ordinary water, but in milk or milk whey. The dosage remains the same. Milk creates a protective film on the leaves and stems that prevents the fungus from spreading to new areas.
Chemicals
Fighting late blight on potatoes with chemicals is an effective way to get rid of the cause of the disease. The disadvantage of this method is its harmfulness. Chemical preparations during processing can get on the skin, mucous membranes, in the respiratory system, therefore, protective equipment should be used. If you overdose or treat plants with them before harvesting, too many harmful substances remain in the tubers, which is harmful to health or leads to poisoning, therefore, when using agricultural chemicals, you must strictly adhere to the instructions.
Treatment of potatoes from late blight is most often carried out by the following means:
- "Artsdil" (50 g / 10 l);
- "Ridomil RC" (25 g / 10 l);
- "Oxyhom" (20 g / 10 l).
When the potato finishes blooming, the foliage and leaves are sprayed with the following means:
- "Ditamin M-45" (20 g / 10 l);
- copper oxychloride (40 g / 10 l);
- "Cuproxat" (25 g / 10 l).
A good effect is given by Spraying with copper sulfate (its norm is 2 g / 10 l), 1% solution of Bordeaux liquid, copper sulfate (20 g / 10 l), slightly pink solution of potassium permanganate and combinations with it.
Folk remedies
If you don't want to use chemistry, you can try one of the folk recipes. These methods are less effective, but in a small garden bed it is quite possible to cope with the fungus, the signs of which have just appeared. The fight against late blight on potatoes with various folk remedies is very popular among summer residents. Here are some interesting ways:
- Garlic is an excellent fungicide that can protect potatoes from fungus. They take 100 g of garlic, insist in 10 liters of water for a day, filter, and then process the potatoes with infusion. To increase efficiency, add a couple of drops of potassium permanganate to the infusion. Spraying is carried out weekly.
- A liter of acidified kefir is dissolved in 10 liters of water, infused for a couple of hours, filtered and treated with a bed. The procedure is repeated 3-4 times in a week.
- Take milk whey, dissolve it in water in a 1: 1 ratio, spray the bushes every 2-3 days.
- Phytophthora is afraid of the common marsh horsetail. Take 100 g of dry or 150 g of fresh horsetail, add a liter of water, bring to a boil and cook for 30 minutes. The broth is filtered and cooled, diluted in 5 liters of water, the field is sprayed once a week.
- 1 kg of hay is soaked in 10 liters of water, having poured a handful of urea there, insisted for 3-4 days. Plants are sprayed with this infusion every 10-15 days.
- The tinder fungus is decanted from the tree, crushed well, pour 10 liters of boiling water and cover with a lid. After cooling, the treatment of leaves and stems of potatoes against late blight begins. The procedure is repeated every 10 days.
- The beds are covered with agrofilm during the growing season.
- Mulch is made from hay or straw: it helps to fight the spread of phytophthora from bush to bush.
- The aisles are sprinkled with wood ash.
If late blight is wound up on potatoes, the bushes are treated until collection, even if the signs have disappeared. With the ineffectiveness of folk methods, they switch to chemicals, otherwise the entire crop will perish. In the fall, before putting the tubers for storage, they are also processed, otherwise it will not be possible to save the crop, all the potatoes will rot. For processing, you can use copper sulfate, iodine, trichopolum or other means.
The next year, potatoes should not be planted in this area. You can sow a field with mustard, lupine, vetch or oats, then dig in these plants so that they fertilize the ground. A year later - to plant corn there. Affected potatoes should never be used for seeds.