Rotting onions? Photos, name and description of diseases + how to deal with them
WHY DOES ONION ROT AND WHAT TO DO? TIPS OF THE SPECIALIST!
Onions are one of the most unpretentious crops.
Even a novice gardener will cope with its cultivation. However, storage of the crop sometimes causes problems - the bulbs rot.
WHY DOES ONION ROT?
SOFT (WET) BACTERIAL ONION ROT usually begins to develop even in the field, closer to the end of the growing season. Mechanical damage to the bulbs - pests and during harvesting, as well as sunburn (which is not excluded in hot weather) contribute to its occurrence. The disease reaches mass distribution during storage, especially when there is a violation of the temperature-humidity regime.
Externally diseased bulbs look healthy: their outer scales are not damaged. Rotting captures the deeper lying scales. They become slimy, acquire a yellowish-brown color and a sharp unpleasant odor. Sometimes healthy and affected scales alternate throughout the bulb. During 2-3 of the month, the bulb rots, infecting others.
The causative agent of the disease persists mainly on plant debris that has fallen into the soil, in the bulbs themselves, and also on the surface of the seeds.
ONION ALTERNARIOSIS often called purple spotting. This disease can also affect garlic and leeks. It intensifies with an excess of nitrogen, high humidity, and often accompanies other diseases. Mostly leaves are affected. However, sometimes bulbs also suffer during storage. Their tissues first become watery, then acquire a yellowish or reddish-brown color, covered with a dark olive coating. The source of infection is plant debris, seeds, and to a lesser extent bulbs.
The pathogen is able to persist in soil on plant debris up to 2 years. The most effective agronomic control measures (3-year crop rotation), preventive treatments and the use of fungicides in case of symptoms of the disease.
ASPERGILLOSIS, IT IS SAME THE DIMENSIONAL MOLD-SHAPED ROT OF ONION, also activated in poorly ventilated rooms at temperatures above 15 °. The disease is especially rampant after a hot and humid summer.
The main symptom of aspergillosis, its calling card, is a black, powdery and dirty mass of spores. Onions lose their presentation. Bulbs can be mummified if wet rot of the bulbs does not join aspergillosis. Under favorable conditions for the pathogen, it quickly spreads to the store. The infection persists in the affected bulbs and in plant debris.
NECK ONION ROT - A real scourge in years with a lot of rainfall, when many varieties of onions do not have time to ripen. The fleshy, unstretched neck of onions, as well as shallots, are open gates for infection. Infection of plants during the growing season with peronosporosis and damage by pests increase the risk of neck rot. And of course, the tab for the storage of insufficiently dried onions.
The disease has a long incubation period. When harvesting, infected bulbs cannot be detected. But later, the color of the covering scales in the neck area will begin to change, and the adjacent tissues will soften, emitting an unpleasant odor. The scales will acquire a characteristic "cooked" look, change color, becoming brownish or grayish. Soon they will be covered with gray, fluffy, powdery coating. The sclerotia formed on it, black small “lumps” of 1-4 mm in size, actively infect the surrounding bulbs.
Sometimes bulbs stored at high relative humidity (greater than 75%) begin to sprout prematurely. In this case, the infection can penetrate through the tissue of the donut disturbed by the sprouting roots.
The pathogen is preserved on plant debris and in the soil, and during the growing season it spreads by conidia, which are easily carried by the wind. There is an opinion that varieties of onions with red scales are more resistant to this disease, as well as varieties with a short growing season and rapid ripening. Nitrogen fertilizers should not be abused, especially in the late stages of the growing season - this greatly delays the ripening of onions.
The most effective protective measures are timely (when most of the leaves dry), cleaning and drying the bulbs under awnings (in favorable weather) or on dryers at a temperature of 30-35 ° for 5-8 days.
Gray Head often accompanied by cervical. The infection penetrates the tissues during the growing season or during the harvesting process and is activated when the regime (temperature and humidity) is violated during storage. Most often, the symptoms of the disease appear on mechanically damaged bulbs, frost-bitten and damaged by pests and rot. Thanks to abundant sporulation, the mushroom spreads very quickly in the storehouse. The protective measures are the same as in the case of neck rot.
See also: Rot (photo disease) - control measures
WHITE (SCLEROCIAL) ROT the bottom of the bulb can appear onion and garlic both in the field and during storage. In the field, the development of the disease is promoted by low (10-20 °) soil temperature
and high humidity. An infection spreads with water, tools and parts of infected plants, which is why the disease is often focal in nature.
The affected bulbs can be easily pulled out of the soil - their root system is almost rotting. A dense white mycelium is clearly visible at the bottom, after some time small sclerotia, about the size of a poppy seed, forms on it, dark, almost black. Often, rot develops first on the outer scales, then spreads to the inner ones. The bulb rots almost completely; the garlic cloves are mummified. In soil, the pathogen persists for up to 10 years. Rot is especially active on soils with a pH of 5,5-5,6 with slight moisture, as well as on bulbs affected by an onion fly.
To combat this infection, in addition to the 4-year-old crop rotation and the removal of plant debris and diseased bulbs, an original method is sometimes used during harvesting and storage. Since in the absence of root secretions of onions and garlic sclerotia germinate poorly, it is possible to process the beds where the disease was discovered with garlic extract. This stimulates the germination of sclerotia. Unable to enter the host plant, they quickly die.
Reference by topic: Why and how does the onion suffer?
DISEASES - CAUSES OF ONION ROT: PHOTOS
WHY BOW ROTS: VIDEO
© Author: I. KORSAK, phytopathologist
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For several years in a row, onions have grown spoiled. The outside looks normal, but rotten rings are found in the cut. How to deal with this?
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- There may be several reasons for this phenomenon:
excessive soil moisture;
violation of the rules of crop rotation and growing onions in one place for several years in a row;
high nitrogen content in the soil.
If you grow onions in the same area, it is most likely that the soil is infected with bacterial rot, bacteriosis, or neck rot.
To break the vicious circle, grow the onions in a new place next season, soak the seed or seeds in a fungicide diluted according to the instructions or a pink solution of potassium permanganate before planting, water the beds only when the ground is thoroughly dry.
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The feathers of the bow were deformed and covered with yellowish dots. What is it? How to save a crop?
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- Most likely, we are talking about rust. If so, then after some time the dots will turn black and the feathers will dry out. Rust is a fairly persistent and contagious fungal disease. Its spores winter well in the soil, and if from year to year grow onions in the same place, rust will attack it every year. Therefore, in the future, be sure to adhere to crop rotation rules. In addition, do not thicken the planting, as the disease is especially active in onions in high humidity.
If signs of rust have been noticed on several plants, pluck and burn them, and pour the bed abundantly with a pink solution of potassium permanganate or 1% solution of copper sulfate.
If the lesion is massive, pour the bed with a solution of HOMA (30 g per 10 liters of water). Repeat the procedure after 20 days.
In addition, do not feed diseased plants with nitrogen-containing fertilizers. Instead, pour a solution of potassium sulfate (1 tsp per 10 l of water) at the rate of a bucket of composition per 1 sq.m. If there is no mineral fertilizer, sprinkle the bed with sifted wood ash (200 g per 1 sq. M).