2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Peronosporosis or downy mildew differs from powdery mildew by the types and names of the causative agents of the misfortune. This disease mainly affects the aboveground green parts of vegetation, and most often it attacks young leaves. Peronosporosis can easily lead to the death of plants, so the fight against it should be started when the first signs of infection appear
A few words about the disease
The causative agents of downy mildew are fungi from the numerous Peronosporaceae family, which in turn gave rise to the name of the unpleasant disease.
When affected by peronosporosis, spots with rather blurred contours and very contrasting colors (pure yellow, grayish-yellow, light yellow) are formed on the upper sides of the leaves. For example, on spinach leaves such spots are colored yellow-green, and on onion leaves they are pale green. A little later, gradually brown spots grow and widen inward, growing through the thickness of the leaves and appearing on their lower sides. On the spots below, a plaque begins to form, resembling flour in appearance - this is a clear indication of the beginning of active reproduction of fungi that produce spores in huge quantities. Plaque can be not only white and whitish, but also gray-olive, light gray, lilac-gray and gray-violet shades.
Degradation of the affected leaves gradually begins: having completely turned yellow, they begin to curl upside down, crumble and fall off prematurely. In infected leaf litter, fungi easily survive the cold.
Peronosporosis spreads to other plants with the help of droplets of rain, air currents, numerous splashes of water for irrigation, with the stirring of crops during their processing. Weeds and excessive crop density also contribute to its spread. With high ambient humidity and poor ventilation, in addition to leaves, the disease can also attack stems with flowers.
How to fight
When choosing varieties for planting, you should focus on the varieties that are most resistant to this disease. Seed should be harvested exclusively from healthy plants.
When planting different crops, it is important to be aware that the same site can be occupied by a particular crop once every three to five years. This rule should be especially strictly observed when growing crops in greenhouses.
One and a half to two months before planting, the seeds are heat treated - for eight hours they are heated with dry air, the temperature of which reaches forty degrees. Or, on the eve of planting, the seeds are immersed in water with a temperature of 48-50 degrees for 20 minutes, after which, after cooling them in cool water for two to three minutes, they are dried.
Presowing seed dressing also gives a good effect. Particularly suitable for this would be a drug called Planriz (for 1 kg - 20 ml).
Severely infected seedlings should be removed and burned in the same way as adult plants. If it is not too badly affected, then before transferring it to the ground, the seedlings are carefully fed with ammonium nitrate (ammonium nitrate).
It is necessary to thoroughly ventilate the plants under glass or film. If the initial signs of the disease are detected, the plants are sprayed with a solution of potassium permanganate (for 10 liters of water - 2 g).
Some gardeners and gardeners, as soon as they notice the first specks, pollinate the plots with ground sulfur (for 10 square meters - 30 g of the substance). Such pollination is carried out at least three to four times.
In order to avoid infection, healthy plants growing in the neighborhood should be sprayed with a 1% solution of Bordeaux liquid, paying special attention to the lower leaves. In this case, infected plants are not sprayed - diseased plants, if found, are immediately removed and burned.
An overdose of nitrogen-containing fertilizers must be avoided in every possible way, it is best to use superphosphate. The use of manure should also be excluded if possible, since manure is a fertile soil for the preservation of fungal spores.
At the end of the harvest, the plots must be cleared of all plant residues, followed by the destruction of these residues.
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