Fusarium onion (PHOTO) - treatment and prevention
FUSARIOS WILFLING OF ONIONS - PREPARATIONS AND PROCESSING AGAINST IT
Despite the fact that onions are rich in nutrients and phytoncides, which are detrimental to various microorganisms, it itself is affected by many phytopathogens - fungi, bacteria and viruses. One of the most common diseases of onions is fusariosis. If you do not start to deal with this scourge on time, you can lose a significant part of the crop.
The causative agents of Fusarium - fungi of the genus Fusarium (F. oxysporum. F. solani, F. equiseti, F. moniliforme. F. conglutinans and others). Population of bulbs with these fungi causes fusarium wilting during the growing season and fusarium rot during storage. The people call this disease "rot of the bottom." Fusarium affects almost all vegetable, flower. fruit and ornamental crops. The causative agent of the disease belongs to soil fungi: in winter it can be in a free state in the form of chlamydospores and in plant debris in the form of mycelium.
The first sign of the disease is the rapid yellowing and death of leaves, starting from the upper tier. The root system is poorly developed, darkened, so the plants lag behind in growth. Most of the roots rot, which makes bulbs easily pulled out of the ground. The bulb becomes soft, watery, in the cut acquires a pink hue. In wet weather, bulbs and feathers affected by Fusarium are covered with a white bloom, which is the sporulation of the fungus. Soon the whole plant withers and dies.
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Typically, the disease spreads foci throughout the growing season. The fungus pathogen can remain viable in soil 4-6 years. Under favorable conditions (low temperature, high humidity in early summer, etc.), the fungus mycelium penetrates the plant through roots or mechanical damage. Through the conducting vessels, the fungus quickly reaches the ends of the leaves, destroying the pectin substances of the vessel walls with its enzymes. The source of infection may be infected plant debris and bulbs.
The development of the disease is promoted by the temperature of the air 20-25 ° C and increased soil moisture. Once in the plant, the fungal spores germinate in the presence of drip dew and infect it. Onion infection occurs on the bottom and on the roots. The pathogen prevents the germination of bulbs, inhibits the development of seedlings and causes the death of leaves.
However, spores of the fungus germinate even at a temperature of 30-32 ° C. Therefore, in recent years, the development of Fusarium wilt has been observed even during the period of air and soil drought - the tips of the leaves slightly dry, the plants weaken. Subsequently, with slight moisture (dew, watering), pathogens become active and infect plants. Leaves instantly become lethargic. Soon, such plants dry out, the bulbs rot.
The spread of the disease is favored by damage to the onion by onion fly larvae or other pests. According to our observations, the development of fusarium wilting of onions in different years ranged from 18 to 35%.
If the infected bulbs get into the storehouse, a plentiful coating develops on them in the tissues of the donut, and the bulbs rot. Onion losses during storage from bottom rot can reach 30% or more.
MEASURES FOR PROTECTING THE ONION FROM FUSARIOSIS
Prevent fusarium will help preventive measures.
Crop rotation should be observed, return the onion to its original place no earlier than five years later.
Before planting, it is necessary to carefully discard diseased specimens. If infected plants are identified in the garden, they must be removed and destroyed before they infect their neighbors. The places where they grew up should be decontaminated: pour 1 with a% solution of potassium permanganate or fill it with a mixture of ash and powdered sulfur.
Whenever possible, try to use varieties resistant to Fusarium.
It is advisable to chalk the soil with chalk or dolomite flour, since the causative agents of the disease do not tolerate an alkaline environment saturated with calcium compounds. During the growing season, it is advisable to feed plants with potassium phosphate fertilizers.
Some vegetable growers recommend using potassium permanganate with the addition of boric acid to protect plants from fusarium wilt. With this solution, in June it is advisable to water the plants abundantly only once (under the root).
Good protection against many types of diseases - seed and bulb treatment
If the tops of the leaves dry out onions, this is the first sign of fusarium with biological (trichodermin, phytocide, planriz) and chemical (foundationazole, quadrice, insurium pro) fungicides.
We have conducted studies to evaluate the effectiveness of fungicidal treatments against fusarium onion wilt. According to the results. the effectiveness of fungicides acrobat MC 69% c. g., Quadris 250 SC, r.p., consento 450 SC. cs, order, s. p., Ridomil Gold MC. at. after double spraying averaged 41-56%. Each fungicide contains systemic drugs that have long-term therapeutic and prophylactic properties. As a result, the protective effect of the drugs lasts two to three weeks. The waiting time before harvesting with quadrice processing is 5 days, with other fungicides —10-14 days.
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When spraying onion plants with fungicides, it is not recommended to use a green feather for food.
After harvesting, the onions must be well dried. Only healthy bulbs should be stored.
Timely and competent implementation of protective measures will help to defeat such an insidious disease as fusarium, and get the expected yield of onions.
Valentina SERGIENKO, candidate of agricultural sciences.
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