Despite all the efforts of breeders, it is not yet possible to defeat plant diseases and they remain a deadly threat to the vine. The most delicious and beautiful varieties are most affected by diseases.
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The most dangerous disease of grapes is mildew, or persporosis, downy mildew. It is common everywhere where there are vineyards, since the causative agent is a fungus that lives on living tissues. He hibernates on fallen leaves and spores right in the soil, easily tolerates heat and frost. Grows at 10 ° C, with wind or rain transferred to the back of the leaf. Generations of fungus per season can be up to 20, and reproduction will stop only with the death of the plant or with a decrease in temperature. The external manifestation of the disease is numerous yellowish spots. The reverse side of the sheet, due to the active propagation of the fungus, is covered with a bloom of mold; this does not occur in dry weather. On resistant varieties, the spots are smaller, dry quickly and look like punctures with a needle with a dried edge, the sheet has an oily sheen. Spots also appear on the shoots, yellowish and then brown, which tend to become moldy.
Varieties with a mediocre taste and high acidity possess genes for resistance to mildew, the most serious disease of grapes. Isabella variety, which has a sharp taste, high content of tartaric acid and unpainted, mucous pulp of berries, is resistant to this disease. When bad taste is diluted by crossing with good grades, disease resistance is also diluted.
Therefore, it is necessary to do the processing constantly, according to the developed scheme and changing drugs for better efficiency.
Especially severe lesions at the tops of shoots on unstable varieties, then the disease affects inflorescences, and fresh ovaries of berries. On more mature berries, the infection looks like a bluish-gray depressed spot under the stalk. Berries turn brown, wrinkle and fall. This disease can be prevented only by systemic preventive treatments.
For successful use, you need to know the classification of chemicals and remember the timing of their use.
Insecticides are used against caterpillars, aphids, beetles and butterflies, and separate preparations against mites - acaricides. Fungicides help against fungal diseases, and herbicides are used against weeds. Contact are those that for action you need to get on a harmful object. Quasi-systemic drugs accumulate on the surface of the treated plants and are released gradually. Systemic penetrate into the cell sap of the plant.
Karbofos is a popular insecticide and at the same time acaricide. It is effective against leafworms and other pests, has a continuous toxic effect and is compatible with Bordeaux liquid and acaricides. Application should take place no later than 20 days before harvest.
Bordeaux liquid is a chemical agent based on copper sulfate and quicklime, a contact agent against many fungal diseases and bacterioses. It is used in the fight against mildew, anthracnose, black rot, rubella, cercosporosis and melanosis. It must be prepared immediately before use, and any winegrower must be able to cook it. Substitutes of Bordeaux mixture are less effective and often faked, and when stored in inappropriate conditions they lose their chemical properties and do not work. Processing should be repeated, since after precipitation the protective properties are reduced and come to naught.