2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Downy mildew of onions, otherwise called peronosporosis, is a very unpleasant and rather dangerous ailment that attacks onions of all types. The bulbs affected by it are very poorly stored, often sprouting during storage. And practically no seeds are formed on infected vegetation. You can face this scourge quite often. It develops especially actively on thickened plantings in cold and wet weather. In order not to lose a significant part of the onion crop, you need to take all the necessary measures against this unpleasant disease
A few words about the disease
Onion leaves attacked by downy mildew form oblong light specks, which quickly become covered with a grayish bloom formed by the spores of the pathogenic fungus. Similar spots are formed on the stems of the testes. On the feathers of onions, as the harmful misfortune develops, the specks begin to turn black.
Oddly enough, the bulbs affected by the malicious scourge have a completely normal appearance. But peronosporosis causes serious harm to the testes. Yellowed infected arrows break down after some time.
The infected surfaces of the leaves (it happens that the bulbs too) are almost always inhabited by secondary parasitic fungi, the result of the harmful activity of which is the formation of a sooty black plaque.
A harmful fungus-causative agent of downy mildew of onions overwinters in infected plants, in affected bulbs, as well as in the roots of perennial onions - the onion is especially attractive for it. Initially, the infection manifests itself in the spring on the onion, when the leaves begin to grow on it.
The spread of the pathogen is noted through the infected planting material (that is, through the seeds and seedlings) through the spores of the pathogenic fungus. The infection is easily transmitted by caring for growing crops, as well as by raindrops and wind. And in hot and dry weather, mushroom conidia die in the sun, without having time to infect the onion.
How to fight
When growing onions, it is extremely important to give preference to resistant varieties and follow the rules of crop rotation. Only 4 - 5 years later, onions are allowed to be returned to their previous beds. Pumpkin and a number of other crops, mineral and organic fertilizers for which were applied in substantial doses, will be excellent predecessors for it.
Excessive thickening of plantings when growing onions should not be allowed. Onion beds should be located in well-ventilated, open and sunny areas with unoccupied, fertile loamy soils. Drainage at the site should also be good. Weed vegetation must be systematically eliminated from the sites. It is equally important to avoid watering at night.
Onions are fed with nitrogen fertilizers only at the initial stage of its development, since they significantly reduce the resistance of this crop to damage by pests and diseases.
It is recommended to warm the sevok thoroughly before planting. This is usually done in the fall, closer to the end of drying. Before sending the collected bulbs for storage, they should be kept at a temperature of forty degrees for eight to ten hours.
Every one and a half weeks, onion beds should be inspected for damage by downy mildew. If infected cultures are found, they are immediately removed.
In order to protect the onion from primary infection with downy mildew, it is sprayed with a systemic fungicide called Ridomil Gold. When the plants form the main vegetative mass, they can be sprayed with Quadris. And for the treatment of seed onion crops, the preparation "Bravo" is excellent.
The onion crop should be harvested in sunny, dry weather, having time to dry the onion before its covering scales begin to dry.
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