The list of possible diseases and pests of onions is quite impressive. Exposure to them largely depends on the variety of culture and compliance with the rules of its cultivation. Diseases and pests must be dealt with in a timely manner, starting with preventive measures.
Onion Disease
Onion diseases can be triggered by bacteria, viruses, fungi. In each case, there are certain features.
Aspergillosis
This disease is fungal. It is also called black mold or black mold. The causative agent is fungi of the genus Aspergillus.
During cultivation, the disease is rarely detected. The only sign is discoloration of the neck of the bulbs - this is the way the pathogen penetrates the fetus.
The main symptoms of aspergillosis are identified during storage of the crop:
- water content of bulbs;
- black powdery mass of spores under the husk, between juicy scales;
- bulbs may completely dry.
Aspergillosis often affects immature and poorly dried bulbs. A high temperature in the storage room and insufficient ventilation in it can also provoke the disease.
Damaged specimens must be disposed of, they cannot be saved.
Preventive measures are as follows:
- burning of plant debris;
- observance of the terms of harvesting - he must fully mature;
- complete drying of the crop;
- compliance with storage conditions: ventilation in the room, the correct temperature and humidity.
Bacteriosis
This bacterial disease can be caused by Bacteriaceae, Pseudomonadaceae, Myconacteriaceae. The affected plant dries out completely or partially, can die.
Bacteria are contained in particles of infected plants. Pests and animals, wind, water for irrigation, rainfall can carry them. The causative agent is also stored in the soil. In healthy plants, it can get through damaged roots, greens, even the slightest wound is enough.
The signs of onion bacteriosis are as follows:
- softening of affected bulbs;
- unpleasant odor;
- small flies;
- in the section, the affected tissues are visible - they are between healthy scales and have a brown color.
More often, bacteriosis affects onions during harvesting and storage. The cause may be damage to the fruit or insufficient drying.
Bulbs affected by bacteriosis must be discarded; they are not suitable for food. To reduce losses, the fruit should be regularly inspected and discarded damaged specimens.
Prevention of bacteriosis consists in the following measures:
- burning of plant debris;
- soil disinfection;
- moderate watering of the crop, its cessation before harvesting;
- harvesting accuracy - fruit damage should be minimized;
- complete drying of the harvested crop.
Smut
This fungal disease is caused by the bacterium Urocystis cepulae frost. Chlamydospores are contained in the soil, can get on seeds with dust. Spores germinate at a temperature of 13-22 degrees, and infection of the culture can occur at 10-25 degrees.
Seedlings are usually affected when planting seeds. The disease is expressed by the following symptoms:
- the appearance on feathers of narrow longitudinal stripes with gray color and swollen epidermis;
- drying of strips with rupture of the epidermis and protrusion of black powder masses;
- the disease can affect adult culture, affecting the external fleshy scales.
Affected seedlings die, resulting in loss of crop. If the bulbs still form, but are infected, then black spores are contained inside. The skin of the fruits crack with time, spores fall into the soil, remaining in it until 5-6 years.
Prevention of smut involves the use of disease-resistant varieties. Crop rotation should also be observed - return the onion to its original place after at least 3 years. Planting a crop with seeds in an infected area is not worth it for 6 years.
Yellow dwarfism
The disease is viral. It is also called viral banding. The Onion yellow dwarf virus causes disease. The virus is in the bulbs, spreads its aphid, the incubation period takes up to 2 weeks.
The disease is expressed by the following symptoms:
- yellow stripes on feathers;
- leaf deformation;
- twisting and lodging of feathers, their flattening is possible;
- strong inhibition of the growth and development of culture.
Affected plants need to be cleaned and burned in a timely manner.
Disease prevention consists of the following measures:
- fight against aphids - actara type insecticides should be used;
- the use of varieties resistant to this disease;
- planting a crop with seeds, including seedlings or seedlings - the virus is not contained in such planting material.
Downy mildew
This disease is also called peronosporosis. The causative agent is the oomycete pseudo-fungi belonging to the peronosporon family. They are stored for a long time in fallen leaves, bulbs.
The signs of the disease are as follows:
- Blurry shapeless or angular spots, a weakly pronounced border is possible. Such formations are pale yellow, tan, red-brown, purple. They are slightly convex, gradually turning brown and dry. The spots grow and can merge into one large spot, occupying the entire sheet.
- Affected feathers bend and dry out, and may crack deeply.
- Spots develop on the one hand, and on the back there is a mild white powdery coating. It may also have a gray or gray-violet color.
- The defeat of peronosporosis usually begins with the upper part of the culture, which is a difference from black spotting, which proceeds with similar symptoms.
Downy mildew is more often manifested in spring. Gradually, it affects all parts of the plant. The development of the disease contributes to high humidity and a temperature drop - low at night and quite high during the day.
Features of treatment depend on the purpose of growing onions. If it is grown on turnips, then you should get rid of the affected plants, and spray the rest. The drug Oxychom is effective. It is necessary to dissolve 20 g of the product in a 10-liter container with water, spraying 2 times a month.
When growing a culture on a feather, spraying with chemicals is unacceptable, therefore, the following measures should be taken:
- stop feeding organic matter;
- temporarily limit watering;
- make potash and phosphorus fertilizers;
- when harvesting, warm it up for 12 hours at 40 degrees;
- treat the crop storage room with bleach - 0.4 kg per 10 liters of water, processing takes 2 months.
Prevention of downy mildew is to comply with crop rotation rules and careful rejection of planting material. When planting onions, sevk should be 2 weeks before sowing, warm it at 40 degrees for 12 hours.
Mosaic
The disease is viral, its causative agent is Allium virus I Smith. The carrier is a four-legged garlic tick.
The signs of the disease are as follows:
- small elongated specks or wide stripes of light green or cream color;
- leaf lag in growth, lodging of a pen;
- bending arrows, the appearance of longitudinal mosaic stripes;
- inflorescence damage: friability, sterility or a small number of seeds.
Damaged specimens must be disposed of. Other methods of control are reduced to the prevention of the disease:
- insecticide treatment for vector control;
- burning of plant debris;
- moderate watering and top dressing;
- crop rotation compliance.
Penicillosis
Such a disease is also called capitate rot or green mold. Its fungi are called Penicillium.
The signs of the disease are as follows:
- the appearance of brown watery spots on the bottom or outer scales;
- gradual softening of affected tissues;
- the appearance of plaque on the affected tissues, first whitish, then green moldy;
- rash of a huge amount of spores when the scales break;
- the affected bulbs appear empty to the touch.
Massively green mold occurs when onions are stored for several months. The process is accelerated at high temperature and humidity in the room. Frozen crops and mechanical damage to the fruit also contribute to the development of the disease.
Damaged specimens must be disposed of. Preventive measures are as follows:
- thorough drying of the harvested crop before laying it for storage;
- compliance with storage conditions - at positive temperature, air humidity should be 60-80%;
- soil disinfection;
- burning of plant debris.
Gray rot
The causative agent of this disease is Botrytis cinerea. The spores and sclerotia of this fungus may contain soil and plant debris.
When growing a culture, the pathogen affects the flakes of the neck of the bulbs, so the disease is sometimes called cervical rot. Contamination is promoted by constant humidity, rainy weather, pests.
The defeat of gray rot often occurs during harvesting, and manifests itself during storage. The development of the disease is provoked by high temperature and humidity in the room.
The signs of sulfur rot are as follows:
- spoilage of fruits begins from the base of the neck, gray rot is visible on the surface;
- if you press next to the neck, this section will be washed out;
- fruit damage is clearly visible in the context: softness, turbidity, usually gray, the flesh looks like after cooking.
If the disease manifested itself during storage of the crop, then the following measures must be taken next year:
- disinfect the soil;
- burn all plant debris if this measure was not taken in the fall;
- when growing a culture, treat with fungicides such as Quadris, Switch, Bravo;
- artificially accelerate the ripening of the crop - to limit nitrogen fertilizers, increasing potassium-phosphorus fertilizing;
- After harvesting, burn off all plant debris.
It is recommended to select cultivars that are resistant to this disease. When planting seeds, pre-seed them.
An onion affected by gray rot should not be eaten. Damaged items identified during storage must be discarded.
Hemophilia
This fungal disease causes Stemphylium allii Oud. More often it is observed in plants that are already affected by peronosporosis.
The signs of the disease are as follows:
- distinct brownish-purple spots;
- heavy bloom on spots first pinkish-purple, then brown;
- breakage of leaves and arrows in affected areas;
- the formation of hollow seeds, the process can stop altogether;
- death of leaves.
Dry and warm weather contributes to the development of hemophilia. The methods of controlling and preventing the disease are similar to the situation with downy mildew.
Fusarium
The disease is caused by fungi of the genus Fusarium. In another way, the disease is called root rot or rot of the bottom.
Signs of defeat are as follows:
- fruit lag in growth;
- the appearance of a pinkish plaque;
- poor development of the root system, brown color of the roots;
- yellowing of feathers, their gradual withering away - the process starts from the tips, but such a sign is not obligatory.
Affected plants must be immediately removed and burned, otherwise the disease will pass on to healthy specimens.
Be sure to treat the culture with a suitable fungicide. It can be Fundazole or Quadris.
Prevention of fusariosis involves the following measures:
- preparation of planting material - treatment with fungicides;
- burning of plant debris;
- soil disinfection - a solution of potassium permanganate, vitriol;
- the introduction of potassium-phosphorus fertilizers - increase the resistance of the culture to the disease;
- compliance with crop rotation rules - onions do not need to be returned to their original place for at least 3 years.
Onion Pests
In addition to possible onion diseases, one should also know about pests dangerous to it. Some of them affect other cultures.
Onion grub
The pest is also called the small daffodil fly. It affects only those plants that have mechanical damage or are affected by other pests. Adults reach an average of 7 mm in length, have a bronze or metallic green color.
The signs of culture damage are as follows:
- growth lag;
- yellowing and wilting of the tops of the feathers;
- softening of bulbs, rotting, the appearance of an unpleasant odor.
Damage to the culture is caused by insect larvae. They appear in June. Bulbs are the wintering site of the pest.
Previously, they used to fight chemicals with onion beetles, but now other methods are recommended:
- timely removal of affected plants;
- watering with a solution of salt - 0.2 kg per 10 liters of water, watering with the growth of the pen to 5 cm, then after 3 weeks.
Prevention is crop rotation and deep digging of the soil in the fall.
Onion fly
This is one of the main problems of onions and other bulb plants. Onion fly is similar to the usual, but ashen color. Insect activity begins in mid-May. It lays eggs in plant flakes and soil. Hatched larvae penetrate into the plant, which serves as their food.
The signs of the pest are as follows:
- withering and drying of feathers;
- slowing plant growth or its complete cessation;
- the appearance of an unpleasant specific smell;
- rotting bulbs;
- white worms under the upper scales of the fruit.
There are several ways to get rid of an onion fly:
- Chemicals. They resort to Aktar (Thiamethoxam), Imidacloprid, Diazinon, Dimethoat, Ripcord. You need to act according to the instructions, the right amount of the drug is dissolved in water and the culture is sprayed.
- Tobacco dust. It can be used for dusting the culture, mixing with ash and black pepper or naphthalene in equal parts. Another option is spraying. It is necessary to dissolve 250 g of the product in 10 l of water, insist for 2 days and treat the plants - 1 l of solution per 1 sq. m
- Ammonia. This method is good in the early stages when a pest has been spotted, but the larvae have just begun to set aside. It is necessary to dissolve 3 tbsp. l funds in 10 liters of water and spray them with culture in the afternoon.
- Kerosene. The tool is detrimental to the onion fly larvae. Enough 50 g of kerosene per bucket of water, you need to spray the soil near the bulbs.
- Laundry soap. It is necessary to dissolve half a bar in a bucket of water. The resulting solution should treat not only the soil, but also the greens.
It’s easier not to fight the onion fly larvae, but to prevent the pest from appearing. Preventive measures are as follows:
- compliance with crop rotation rules - do not plant onions after other plants of this family, do not return it to its original place of planting for at least 3 years;
- digging the site in the fall on a full bayonet of a shovel;
- alternating beds of onions and carrots - both cultures have their own kind of flies that cannot tolerate the smell of such a neighborhood;
- processing of planting material - 2 minutes of soaking in a solution of potassium permanganate is enough;
- regular loosening of the soil - flies do not like loose soil, so they don’t lay eggs there;
- preventive treatment of plantings with wood ash, tobacco dust, laundry soap.
Onion tick
It is difficult to notice such a pest with the naked eye because of the whitish color and small size - about 1 mm. An insect appears at high temperature and sufficient humidity.
The defeat of the culture can be identified by the following signs:
- deformation of feathers, the appearance of white plaque;
- bulb dehydration and puckering;
- the appearance of yellow spots on the bulbs;
- the friability of the fruit, the appearance on them of larvae resembling dust;
- mold may appear in the affected areas.
Onion mite can harm not only the culture, but also the person. It can be an allergic reaction, asthmatic complications, digestive upsets.
You can deal with a pest in the following ways:
- treat with chemicals - you need to resort to acaricides and insectoacaricides;
- Get rid of affected plants regularly.
You can disinfect affected bulbs by heat treatment - lower them for 5 minutes in water heated to 45-50 degrees.
It is not easy to get rid of an onion tick, therefore it is important to follow preventive measures:
- processing of planting material - heating at 35-40 degrees for a week;
- harvest rejection - all specimens with the slightest signs of damage for storage are not suitable;
- treatment with nettle infusion - brew leaves in boiling water in a ratio of 1: 5, insist 5 days, then dilute in 10 parts of water and spill the culture under the root;
- disinfection of the premises for storage of crops, the organization of ventilation in it;
- pruning greens before storing.
Tobacco thrips
The insect is also called onion. In addition to onions, it is dangerous for garlic, cucumbers, gourds, flowers. The length of the adult is about 0.8 cm, the edges are fringed, the body is narrow and elongated, the color is light yellow or dark brown. Larvae have no wings, the color is whitish or greenish-yellow.
The harm is mainly caused by larvae and females of tobacco thrips. Their nutrition is the cellular juice of plants.
Signs of defeat are as follows:
- angular spots, first light, then brown;
- black dots of excrement at the bottom of the spots;
- curvature of the affected pen, yellowing of the tips;
- growth retardation.
If tobacco thrips is affected, the crop suffers, therefore it is necessary to deal with this pest:
- insecticides for processing: Aktara, Actellik, Fitoverm, Fufanon;
- sticky traps - apply special glue for insects on strips of yellow or blue cardboard and place them in the aisles;
- spraying tobacco leaves with infusion - grind dry raw materials, add a little water, insist 3 hours, after filtering for another 36 hours, dilute in two parts of water for spraying;
- celandine - drop 100 g of dry grass in a liter of water; go 400 g of fresh stems and flowers, insist 3 days, use for spraying;
- sulfur for fumigating the premises where the onion will be stored - 1 cubic meter. m need 60 g of substance.
Prevention of the appearance of tobacco thrips involves the following measures:
- compliance with crop rotation rules;
- burning of plant debris - the pest overwinters in them;
- digging the site in the fall - it is better to dig a full bayonet, the pest for wintering is deepened by about 7 cm;
- weed removal - insect nutrition in spring;
- heating of planting material - two days at a temperature of 40 degrees.
Proper cultivation of onions and timely prevention of crop damage by diseases and pests avoids many problems. They cannot be ignored, since the qualitative and quantitative characteristics of the crop will suffer, the duration of its storage will decrease, and losses over this period will increase significantly.