Onions can affect various diseases and pests, because of which the plant rots and turns yellow. Also, a violation of the rules of agricultural technology or storage of crops can provoke this problem. Next - the problems of decay and their solution.
Agrotechnical causes of yellowing and rotting of onions
Not always yellowing of leaves and decay of onion turnips indicate damage to the plant by a disease or pests. The reason may be a violation of agrotechnical measures for the application of fertilizers, irrigation, adverse weather conditions.
Excess moisture
Onion is a fairly moisture-loving crop. In the period of intensive growth and development, it requires maximum irrigation. The rate of feather and turnip formation depends on the amount of moisture in the soil. But already in the 2nd period of vegetation, its excess leads to the development of putrefactive bacteria.
Prevention measures:
- compliance with irrigation technology;
- cessation of watering 2-3 weeks before the planned harvest.
Ways to combat excess moisture:
- with abundant rainfall, cover the onion planting with a film;
- build drainage trenches - pour the bottom with sand, which serves as drainage, plant onions on the sand and sprinkle with a layer of earth (this method is ideal for clay areas).
Excess or lack of fertilizer
When growing onions, like other crops, an important point is to maintain a balance of nutrients. Deficiency or excess of each of them has a negative effect on the plant.
Signs:
- nitrogen deficiency leads onion feathers to softness, pallor and decay;
- phosphorus - slows down the growth of the plant, the leaves become variegated, bulb ripening is inhibited;
- potassium - the leaves turn slightly yellow, the tops twist and die, the lower leaves become corrugated, brown and dry, the onion forms a thin scale;
- copper - Thins the pen, makes it pale, slows the growth of the plant, thickens the neck of the onion;
- zinc - leads to dwarfism of plants, leaves twist and spread on the surface;
- bora - the feathers are sharpened, the young ones turn yellow, and the older ones become gray-gray-green.
The reasons:
- nitrogen deficiency causes excessive watering, increased soil moisture;
- phosphorus - observed on clayy, poorly drained soils;
- potassium - leads the fixation of the element by the soil, exacerbates increased humidity, followed by heat;
- copper - most often observed on peatlands, with excessive introduction of manure;
- zinc - It happens on soils with an acidity of pH 7.5-8;
- bora - most often observed in closed ground.
Prevention measures:
- carefully select the site, control the acidity of the soil;
- do not introduce manure and humus;
- strictly observe the quantity and timing of the application of mineral fertilizers;
- organize soil drainage and removal of excess moisture.
Ways to combat the excess or lack of trace elements:
- With a lack of trace elements, wet dressings are produced with the substances the plant needs. Fertilizer is bred in a bucket of water according to the instructions.
- If the plants are severely depleted, the fertilizer solution is made more concentrated than with planned top dressing, but not higher than 1%. Plants react immediately.
- With an excess of trace elements, it is almost impossible to help the plant. Water partially flushes out excess trace elements from the soil, so watering is the only salvation.
Crop rotation failure
The key to a rich harvest of any crop is crop rotation. Each of the crops grown on the site exerts its influence on the soil. If you choose the right predecessors, then you can minimize the harm of diseases and pests.
The main condition for organizing crop rotation of onions is the return of culture to the same place no earlier than 3 years later.
Signs:
- reduced resistance to diseases and pests;
- friability of bulbs;
- susceptibility to decay.
The reasons:
- planting onions in the same place more than 2 times in a row;
- the choice of a predecessor with diseases and pests characteristic of onions.
Prevention measures:
- A selection of predecessors that were plentifully fertilized with organic fertilizers. The best are potatoes, cucumbers, cabbage, legumes, greens.
- Avoid planting onions after radishes, celery, carrots, leeks.
- Carefully select crops adjacent to onions. The best neighbor of onions is carrots, it is also good to plant parsley, celery and marigold near onion plantings.
Unsuitable weather
Bulbs decay from rains, greens wither, and feathers turn yellow and dry from heat. The reasons for this are excess moisture or drying out of the soil.
Prevention measures:
- moderate watering when heat is established;
- the use of covering material in rainy weather (as much as possible).
Causes of bacterial and fungal nature
Numerous diseases of bacterial and fungal nature significantly reduce onion productivity. Different types of rot, bacterial infections affect the leaves, turnip and roots.
Cercosporosis
The causative agent of the disease is the imperfect fungus Cercospora duddiae Welles. Winters in the remains of vegetation and seeds. Spread by wind and raindrops.
Signs of the disease:
- on leaves sharply defined roundish or irregularly shaped spots of grayish-brown color with a yellow border;
- the leaves turn yellow and gradually die off, reducing yield.
The reasons:
- wind and raindrops spread the infection during the vegetation of plants;
- non-observance of cleanliness on the beds (plant residues are present);
- the use of contaminated seed material.
Prevention measures:
- use high-quality planting material;
- fungicide treatment of planting material;
- crop rotation compliance;
- seedling treatment with copper-containing preparations;
- removal of diseased plants from the garden;
- timely weeding;
- heat treatment of planting material by heating seeds at a temperature of 40-45 degrees for 6-8 hours.
Treatment:
- Preparations Fitosporin, Fito-plus, Bordeaux fluid, copper sulfate;
- Also used infusion of fermented grass. Grind the grass (without soil), fill it with half a bucket, fill it with hot water. After a few days, strain and process the beds.
- Dairy products are diluted 1:10 with water and are treated in the evening.
Do not use onion leftovers in compost heaps or as fertilizer. At the slightest sign of putrefactive disease, affected specimens are disposed of outside the beds.
Bottom rot (fusarium)
The causative agent of the disease is the phytopathogenic fungus Fusarium oxysporum f. Sp. It develops at high soil temperatures.
Signs of the disease:
- twisted and yellowed leaves;
- the root system turns brown, sometimes becomes hollow;
- in a section on the lower layer of the bottom - a watery brown spot;
- the root system can rot, the bulbs are easily removed from the soil.
The reasons:
- moving contaminated soil in inventory;
- infected irrigation water or planting material (onion sets);
- damage to the roots, bottom or bulbs of onion fly larvae or other insects.
Prevention measures:
- planting of resistant varieties;
- crop rotation compliance;
- fertilizer control;
- before laying for storage onion processing Fitosporin;
- peeling bulbs from the top layer of scales;
- dressing of seed material in a solution of Fundazole or Quadris;
- Once a week, water for irrigation is replaced with a solution of any fungicide;
- in the fall they cultivate the soil with such preparations as Ridomil-Gold, Acrobat-MC.
Treatment It is complicated by the fact that the diagnosis of the disease is delayed. Most often, the disease becomes known when the irreversible effects begin. Therefore, be sure to observe preventive measures.
White rot
The causative agent of white onion rot is the pathogenic fungus Sclerotiumcepivorum Berk. It affects not only crops, but also carries a threat to the harvested crop during storage.
Signs of the disease:
- seedlings turn yellow and die;
- white fluffy plaque of mycelium (mycelium) appears on the roots and scales;
- wet rot develops, “poppy seeds” appear on the surface of the affected area - sclerotia.
The reasons:
- violation of the irrigation system or rainy summers;
- the use of infected and poor-quality planting material;
- untimely removal and destruction of infected plants from the field.
Prevention measures:
- crop rotation compliance;
- maintaining the moisture regime during the onion growing season;
- the use of healthy and quality planting material;
- treat planting material with copper-containing preparations.
In the treatment pour onion beds with milk serum - dilute 1.5 teaspoons of copper sulfate in 1.5 liters of serum and add 3.5 liters of water. In extreme cases, systemic fungicides are used:
- Fundazole;
- Home;
- The order;
- Privikur.
Neck rot
The causative agent of neck rot is the spore Botrytis allii. In conditions of high humidity, spores are rapidly reproducing on dead and decaying plant debris. In rainy and warm weather, wind and raindrops dispute everywhere.
The disease is detected in most cases, 1-2 months after bookmarking for storage.
Signs of the disease:
- the affected neck is soft and porous;
- on the upper scales there are dented spots;
- the bulbs are covered with gray mold with black spots;
- scales wrinkle;
- the bulb dries up.
The reasons:
- wet summer, watering during the ripening period of the bulbs;
- excessive application of organic and nitrogen fertilizers;
- non-observance of agrotechnical timing of sowing (early onion planting is recommended);
- thickening of crops;
- non-observance of the cleaning terms (being late with the cleaning work often coincides with inclement weather);
- violation of storage modes.
Prevention measures:
- introduction of manure and nitrogen fertilizers for crops;
- compliance with the timing of landing;
- prevent thickening of plants;
- observance of cleaning terms;
- preparation for storage (dry, remove dried leaves);
- destruction of plant residues after harvesting.
At the first symptoms of neck rot, pour the beds with 1% Bordeaux liquid (dilute 100 g in 10 liters of water). Also watered with Kvardos (8 ml of the drug is diluted in 10 liters of water).
Downy mildew (peronosporosis)
One of the most dangerous diseases. It is caused by the phytopathogenic fungus Peronospora destructor. During wet weather there is a rapid process of development and sporulation. Wind and rain are spreading controversy everywhere.
Onions are affected at any time during the growing season. As a result of the disease, productivity decreases, aging and keeping quality of the culture worsen.
Signs of the disease:
- in the first 4 weeks, the feathers of such an onion do not develop well, turn pale, then turn yellow and bend;
- in dry weather, the leaves are covered with pale green oval spots, in wet - gray-purple bloom (fungal spores).
The reasons:
- excessive watering;
- adverse weather conditions;
- accumulation of post-harvest plant debris on the site.
Prevention measures:
- use high-quality planting material;
- fungicide treatment of planting material;
- crop rotation compliance;
- seedling treatment with copper-containing preparations;
- removal of diseased plants from the garden.
In the fight against powdery mildew, the beds are treated with an interval of 7-8 days with the microbiological preparation Fitosporin-M (15 ml / 10 l of water), 1% copper chloroxide, Bordeaux liquid or a mixture of copper sulfate.
Folk remedies are also used:
- Wood ash, tincture of weeds (any weeds are poured into a bucket, insist 5 days, filter and water the plantings).
- Dairy products containing sour milk bacteria have a detrimental effect on the spores of the fungus. For watering, dilute whey, yogurt in water 1:10.
Pest
Pests are a great danger. Even slight damage to the bulb entails the development of diseases, yellowing or rotting of the vegetable. Malicious insects not only damage the crop, but also cause food allergies in humans.
Onion tick
A pest of the arachnid class, a family of flour mites. Very tenacious insect. An onion mite can be without food for a long time or eat decaying plant debris. At low or high temperatures, it falls into a state of suspended animation. The powerful sucking oral apparatus of the tick sucks moisture from the onion scales.
Signs of the disease:
- stalk deformation;
- the appearance of bright spots on the leaves;
- at the time of “occupation” of plantings by females, the plants are covered with “plaque” - mite bodies;
- the bulb dehydrates and coarsens;
- often plants are affected by rot and mold.
The reasons:
- failure to conduct planting material processing activities;
- ignoring sanitization of storage facilities;
- accumulation of plant debris in the garden;
- failure to comply with the landing dates;
- violation of agrotechnical measures for tillage.
Prevention measures:
- creating a grass barrier;
- treatment with herbal decoctions of nettle;
- autumn digging of the soil;
- disinfecting treatment of storage rooms;
- heating of planting material for one week;
- processing of seed material with colloidal sulfur before planting.
The fight against onion mites with folk remedies and general insecticides does not bring tangible results. When using drugs of unidirectional action, ticks develop immunity.
Onion Secretive Hunter (Weevil)
Onion crypto-hunter - black beetle 2-2.5 mm long. With a long proboscis nose sucks the juice from the plant. Larvae gnaw onions from the inside.
Signs of the disease:
- the plant becomes covered with silver spots and dies;
- at high humidity, an olive bloom is observed.
The reasons:
- non-compliance with agricultural technical measures for crop care;
- lack of sanitary conditions in the garden (accumulation of vegetation residues).
Prevention measures:
- planting onions in well-ventilated ridges;
- loosening and weeding of beds;
- watering the aisle with water with the addition of ground hot pepper, wood ash, dry mustard;
- soil treatment with a mixture of wood ash, red pepper or dry mustard (2: 1);
- processing plantings Karbofosom (60 g per 10 liters of water);
- to plant onion-batun between the beds as a bait (as infection becomes, the bait is cut off and removed from the garden);
- harvesting the remains of vegetation from the beds in the fall.
Methods of struggle:
- during the growing season is treated with a solution of Karbofos (60 g per 10 liters of water). A liter of solution is enough for 10 square meters. m landings.
- Fold in the evening the burlap tape (10 cm wide), wrapping them in the bulbs. In the morning, remove the tape in which the pest gets entangled.
Onion thrips
Onion thrips (Thrips tabaci) - a small insect 0.8 mm long brown, has wings with a fringe. Larvae are greenish in color, have no wings. Thrips and its larva feed onion juice.
Winters in the upper layers of the soil or the remains of plants. In early spring, females lay their eggs. The larva has a diet like an adult. The peak of thrips activity is dry, hot weather.
Signs of the disease:
- whitish and silver spots are present on the leaves;
- the leaves bend, turn yellow and fade.
The reasons:
- crop rotation failure;
- violation of agricultural activities;
- violation of sanitary measures for preparing seed for planting.
Prevention measures:
- compliance with agricultural activities;
- thermal disinfection of planting material (exposure to water 40-45 ° C for 10 hours);
- soaking planting material in a solution of sodium nitrate for 24 hours;
- drying onions before laying them at a temperature of 35-37 degrees for a week;
- harvesting plant debris from the garden;
- laying traps between plants;
- planting around marigold onion beds;
- processing of beds with celandine infusion (cut celandine stems insist in water for 48 hours).
Methods of struggle:
- lay out cardboard strips painted in blue and smeared with glue for pests;
- process plantings with infusion of onions and garlic (1 tbsp. chopped onions or garlic in 1 cup of water);
- insist tobacco leaves in a small amount of water, leave the filtered infusion for another 3 days, dilute in water 1: 2 and process the plantings.
Onion fly
The insect is gray in color, outwardly resembling an ordinary fly. Lays eggs in late May in the upper scales of the bulb, plant or in the soil. Larvae feed on fleshy onion scales. During the summer, three offspring of a fly grow, the bulb rots. And the larvae are the most dangerous threat.
Onion fly larvae live not only in onions, but also in garlic and flower bulbs.
Signs of the disease:
- the bulb rots;
- leaves turn yellow and die;
- a putrid odor appears on the beds.
The reasons:
- crop rotation failure;
- violation of agricultural activities in the form of autumn digging;
- infected planting material;
- neglect of disinfection of planting material.
Prevention measures:
- planting onions next to carrot beds (the specific smell of carrots repels the onion fly);
- soaking seeds before planting in saline;
- watering with a solution of salt;
- regular loosening of the soil;
- pollination with tobacco infusion (insist 400 g / 10 l of water for 48 hours, boil for 2 hours, strain and add another 10 l of water, add 100 ml of liquid soap and process 3-4 times during the growing season);
- destruction of plant debris;
- late digging of the soil;
- liming of the soil after digging and before planting.
Methods of struggle:
- spraying plantings with strong-smelling infusions: mint, needles, valerian, tomato leaves, wormwood, lemon balm;
- sprinkle plantings with ash or tobacco dust, preferably after rain;
- water the onion beds with saline in 3 doses: the first watering - when the plant reaches 5 cm, the second - after 2 weeks, the third - 3 weeks after the second treatment.
Onion and stem nematode
Nematodes are a family of parasitic roundworms that lay eggs in bulbs. Developing offspring feeds on the juice of the bulb, which causes the death of the plant.
Signs of the disease:
- bloated and twisted falsely stalk;
- in the context of the bulb is friable, granular structure of fleshy scales;
- uneven thickening of scales;
- the scales turn white and then become brownish or gray;
- the bulbs are moist and have a garlic odor.
The reasons:
- the use of nematode infected planting material;
- nematode-infected soil;
- the use of contaminated equipment (choppers, plows, harrows);
- infected remains of previous crops, weeds.
Prevention measures:
- crop rotation, return of crops affected by the nematode to the same place no earlier than 3 years later;
- soil treatment with a solution of Carbation (200 ml per 1 sq. m);
- selection of healthy, nematode-infected seeds for planting;
- heat the seed material by immersing the bulbs in water at a temperature of up to 50 ° C for 8-10 minutes;
- watering for 2 weeks with a light pink solution of potassium permanganate;
- timely weeding of crops from weeds;
- introduction of dolomite flour into the soil for its deoxidation;
- peat and sand are added to make the soil friable;
- during the growing season, 2-3 treatments with Abamectin.
Ways of struggle:
- Folk remedies in the fight against the nematode are limited to heat treatments of planting material and plantings.
- Chemical treatment is effective:
- Carbation;
- Chloropicrin;
- Nemagon;
- Methyl bromide, etc.
Why does onion rot during storage?
Onions often rot not only during the growing season, but also during storage. If you find rotten or yellowed elements, sort out the crop and remove all damaged bulbs. Also eliminate the factors that triggered the problem.
Wet bacterial rot
The causative agent is the bacterium Dickeya chrysanthemi or Pectobacterium carotovorum subsp.
Signs of the disease:
- spots from light to brown form around the root neck;
- the fabric becomes soft, when pressed, it releases fluid;
- there is a specific smell;
- in the context of healthy scales alternate with the affected;
- rot grows from the center of the bulb, and after a while all the scales become mucous.
The causes of the disease:
- poor selection of varieties for planting;
- non-compliance with irrigation, temperature and nutrition.
The bacterium penetrates the inside of the bulb through:
- mechanical damage to the bulbs during soil cultivation or during harvesting and transportation to the storage place;
- damage to the bulb by insects, or places of sunburn.
Prevention measures:
- crop rotation compliance (discussed above);
- culling affected bulbs before planting;
- observance of agrotechnical methods of rotation (sowing dates, depth and distance of seeding, irrigation and top dressing);
- compliance with harvesting rules (to collect onions in dry weather during the period of mass lodging and yellowing of the feather);
- Only healthy bulbs should be stored;
- compliance with the appropriate level of humidity and temperature during storage, as well as sanitary conditions in the room.
Black mold rot (aspergillosis)
The causative agent of the disease is Aspergillus niger. It spreads by air through contact.
Signs of the disease:
- blackening is formed in the neck;
- the bulb becomes soft;
- the scales dry, and black rot appears between them.
The causes of the disease:
- bulbs that are unripe and improperly prepared for storage are exposed to the disease;
- violation of storage conditions (elevated temperature and humidity, poor ventilation).
Prevention measures:
- fungicide treatment of planting material;
- treatment of crops with Bordeaux liquid 3 weeks before harvesting;
- compliance with temperature and humidity conditions in storage rooms;
- eliminate damage to the bulbs in the form of scuffs.
Green mold rot (penicillosis)
Called by pathogenic fungi of the genus Penicillium in a warm and humid environment. It appears in 2-3 months after laying in the onion storage areas.
Signs of the disease:
- a wet pale yellowish spot appears on the bulb, gradually becoming covered with a blue-green bloom;
- on the incision of the bulb there are yellow-brown or gray watery spots;
- a musty smell of mold appears.
The causes of the disease:
- mechanical damage;
- sunburn;
- frosted bulbs;
- high humidity during storage.
Prevention measures:
- drying the crop before laying it for storage;
- compliance with humidity during storage;
- prevent mechanical damage and frostbite onions.
Anthracnose
The causative agent of the disease is Colletotrichum circinans. Heat and moisture are supporters of the propagation of the candidias of this fungal disease. And wind and rain carry them around the site. At the storage site, the disease continues to develop.
Signs of the disease:
- concentric rings form around the neck of the bulb;
- small yellow spots form on the inner scales;
- the bulb wrinkles and sprouts.
The reasons:
- the use of low-quality planting material;
- crop rotation failure;
- poor preparation of the crop for storage;
- violation of storage modes.
Prevention measures:
- planting varieties of onions with golden and red coverslips;
- the use of high-quality planting material;
- crop rotation compliance;
- observance of the terms and methods of cleaning;
- treatment of planting material with fungicides.
When cultivating onions, remember that the sooner the cause of the “malaise” of the crop is identified, the higher the chances of saving the crop and preventing soil contamination. Strictly observe the agrotechnical processing time against diseases and pests, so as not to leave them the opportunity to destroy plants.