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Yellowing Onions. What To Do?

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The onion is a vegetable crop that grows literally in every vegetable garden, and almost every gardener sooner or later faces the problem of yellowing feathers of this plant. There are many reasons for this phenomenon, but only one can be perceived by gardeners quite calmly - when the feathers turn yellow and fall when the bulb is ripening. All other reasons for the yellowing of onion shoots are unacceptable, and they must be known and be able to eliminate, otherwise you can be left without a harvest. But before we take up the causes and start learning how to eliminate them, let's talk about how to keep your onions from yellowing their feathers as safely as possible.

Yellowing onions. What to do?
Yellowing of onion stems. © Sven Spichiger


  • Simple rules of prevention against onion feather yellowing
  • Pests that cause onion yellowing
  • Onion diseases
  • Mistakes in onion bed care

Simple rules of prevention against onion feather yellowing

So, For onion feathers to be a healthy color until the harvest, it is necessary to treat the plot correctly, water in time, use modern means of disease and pest control and consider other rules of its cultivation.

Rule one - observing crop rotation

Remember that it is not recommended to plant onions in the same place more than once every four years, otherwise pests and diseases accumulate on the plot, and the onions consume plenty of nutrients from the soil.

Rules two - correct fertilizer

Perform the fertilizer correctly and in optimal amounts, remembering that both the lack and excess of fertilizer does not promise anything good. You should not allow the soil to dry out too much and significantly overwater the soil too.

Rule four - do not run the site

If you notice that the onion feathers began to turn yellow, it is better to remove them and burn them. So you can stop the infection or pest spreading.

Rule five - deep digging

The soil for onions should preferably be dug to the full bayonet of the spade with a revolution of the layer to minimize the number of harmful microorganisms in the soil.

These are essential measures, we can say, to prevent yellowing feathers onions, but it also happens that they do not help, and the onion still turns yellow. What are the causes and what to do about it?

Yellowing onions. What to do?
Mildew on the onion. © Levon

The reasons for the yellowing of onions, as we have already mentioned, are quite numerous, it can be a manifestation of pest or disease, improper agricultural techniques, the effects of weather or a lack of nitrogen in the soil.

Pests causing yellowing of onions

Pests, the vital activity of which leads to the yellowing of onions, quite a lot: it onion moth, tobacco thrips, onion concealer, stem nematode and, of course, onion fly.

Onion moth

An onion moth is usually most active when the heat and rarely rains, the soil is over-dry. At this time, the onion moth butterfly appears, little different from the domestic moth we are all familiar with. Its larvae, which hatch from eggs laid by the moth, cause damage. The presence of larvae leads to the fact that first the tips of onion feathers begin to wither, and then the entire feather dries up.

In order to know how to fight the onion moth, you need to know its biology. For example, the onion moth makes its ovipositor near the bulbs into the soil. Caterpillars hatching from eggs have a light yellow body color and are about a centimeter long. Hatching, they move to feathers, get into them and begin to gnaw out the tissue from inside, which leads to the yellowing and wilting of feathers.

Before using insecticides such as Metaphos, you should try to fight the onion moth with folk means, for which you can treat feathers and the soil around with furnace ash, scattering it evenly, and also with tobacco, you can directly from cigarettes, or spray the soil and plants with garlic infusion (a couple of cloves per liter of water).

Yellowing onions. What to do?
The onion moth butterfly (Acrolepiopsis assectella). © Larry Hodgson

Tobacco Thrips

The onion, or tobacco thrips, also causes yellowing of onion feathers. Thrips are smaller in size than aphids and, like them, feed on cell sap, which leads to yellowing and desiccation of onion leaf blades. Thrips overwinters in the soil and bulbs that are left for planting the next year, so even if you plant seedling in an ideal plot in all respects and observing all the agricultural technology, onions can still suffer from this pest.

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In order to thrips in your area did not get with the sowing, it is necessary to drop the sowing for a quarter of an hour before planting in water with a temperature of 45-47 degrees above zero, then for 10 minutes - in cold water.

If the pest announced clearly, the folk remedies are unlikely to help, then you must use insecticides. To control thrips, you must use insecticides, strictly following the instructions, such as Spark or Confidor.

Yellowing onions. What to do?
Tobacco thrips larvae on onions (Thrips tabaci). © Travis Cranmer

The Onion Latent Thrips

Their activities are another reason why onion feathers can turn yellow. The larvae of the stealth moth literally eat the feathers of onions and they first change color to lighter, then turn yellow, wilt, and die. If the pest is not dealt with, it can destroy most of the onion plantation.

The most annoying thing is that this beetle moves quickly, and even if you consider crop rotation, fertilization and watering, and take good care of the soil, it can still appear on your plot, having flown from the neighboring one.

To minimize the risk of the beetle on the plot, it is necessary to recultivate the soil, remove and burn plant residues, and observe crop rotation. The soil around beds should be sprinkled with wood ash or mustard or pepper powder, which can repel the insect.

If the beetle appears in small numbers, these individuals can be picked up by hand. If the pest is numerous, however, it is necessary to apply insecticides, strictly following the instructions on the package. Earlier, the drug Karbofos helped effectively, but then it was banned and you need to look for other approved analogues.

Stem nematode

The next reason for the appearance of atypical color of onion feathers is a stem nematode. It is essentially a small worm that can penetrate the bulb and cause cracks in the bottom of the head, it begins to rot and the leaf lamina begins to turn yellow and die off. Usually the nematode is very small, no more than one and a half millimeters, but the damage from it can be tremendous. If the nematode gets into your plot, no crop rotation is likely to help, it can live in the soil for up to ten years, and sometimes longer.

To exclude the nematode by means of seeding onions into your plot, it should be dropped for a quarter hour in water heated to 45 degrees above zero before planting, and then in salted water for half an hour.

Horticulturists say that if the soil is infested with nematodes can help get rid of it with infusion of velvet grass - 2-3 kg of vegetative mass of velvet grass per bucket of water is the norm for 2-3 square meters of soil.

There are also insecticides to combat nematodes, these are Fitoverm and a new drug Nematophagin BT.

Yellowing onions. What to do?
Onions infested with nematodes. © H. de Belem

The onion fly

Almost the most common pest of onions, the larvae of which are happy to eat any of its varieties. Usually you can determine that it is the onion fly to blame for yellowing feathers by the way the leaves begin to deteriorate: first they turn yellow, then they begin to wither.

In order to prevent the onion fly in the plot, beds with onions should be alternated with beds of carrots. The scent of carrots can repel onion flies, and the smell of onions - carrot flies, here is a double benefit.

If the number of individuals is small and the harm from them is not yet very significant, the affected plants can be treated with a solution of salt and ammonia alcohol, but remember that salt is dangerous for the soil and more than once a season such treatment is better not carried out. To obtain the solution you need to dissolve 200 grams of salt in a bucket of water (no more!) and a tablespoon of ammonia alcohol. After that, you can treat the soil and the affected plants with the solution, using this amount per five square meters of bed.

Mixtures of ash and tobacco, pepper and mustard in equal proportions are much more favorable for soil, but less effective for the pest. You may use 25-30 grams of these substances per square meter.

If traditional remedies do not help, which is often the case, you must use insecticides. Onion flies can be treated with the following preparations: Actara, Sochva and Tabazol.

Yellowing onions. What to do?
Signs of onion infestation by leek or onion flies. Onion diseases

In addition to pests, diseases such as bacterial blight, blight, rust and a number of other less common ones can also turn onion leaves yellow. Usually the diseases on onions are fungal or bacterial, and they can appear on the site being brought in with the planting material or by insects.

Bearing this in mind, when sowing onions, seedlings should be carefully screened by removing all those bulbs that show signs of infestation. The remaining bulbs should be placed in water at +45 degrees for 10-15 minutes, then dip them in salt water (a tablespoon per 300 grams of water) for 8-10 minutes.

Do not forget that diseases are more active in the soil having excess moisture and in shaded areas, so water onions often but sparingly and pick levelled and well lit area.

In addition, diseases can be transmitted with pests, so even if there are few pests on the plot, you still need to deal with them.

If you don't want to use chemicals to fight the diseases, at least treat the affected plants with copper-containing preparations: XOM, Oxyhom, Bordeaux liquid and others, if that is not appropriate in your plot either, then remove the affected plants to not let the diseases spread further.

Yellowing onions. What to do?
Rust on onions. © Sue in Suffolk

Onion bed care mistakes

Any plant can suffer from improper care and onions are no exception. The most common mistakes are planting onions in the same spot for many years, improper fertilizing and watering.

Lack or excess of nitrogen in the soil

Onions are almost the only vegetable that is very picky about nitrogen in the soil. Onions can turn yellow both from a lack of nitrogen and from its excess, so you should be careful with the introduction of micronutrients. If feathers turn yellow, dig up one bulb, if you do not find signs of pest infestation and the bulb is apparently intact, it is possible that the feathers turned yellow due to a lack of nitrogen.

For its replenishment you must spend foliar feeding: enough to dissolve 45-55 g of ammonium nitrate in a bucket of water and spend the resulting solution for a couple of square meters of onion bed. Nitroammofoska can be used for this purpose by dissolving a tablespoon of fertilizer in a bucket of water, this amount is enough for three rows. In this case, superphosphate and potassium sulfate should be added to the soil. Both need a teaspoon per bucket of water, this is the norm for a couple of square meters of bed. After a week, you can loosen the soil and add wood ash to 100-150 grams per square meter.

We do not recommend to bring organic matter under the onions, especially if the summer is wet and cold, this can lead to outbreaks of fungal diseases.

Wrong onion watering

If onions under or over water, his feathers begin to turn yellow. Onions should be watered every day, preferably in the evening, with tap water at room temperature. A bucket of water per square meter is enough, but only if it is not raining and it is hot. If it rained even a little during the day, you can not water, if there is no rain, but it is cold (below +20 degrees), you can halve the amount of water.

Yellowing onions. What to do?
Onion bottom rot

Closing. So, as you have understood, the reasons why onions start to turn yellow feathers, quite a lot. Before you take on chemicals, assess the condition of the onion, try to find pests, assess the condition of the soil and so on, only then decide in favor of using chemicals. Sometimes the situation is saved by simply removing a few atypical plants from the plot and following some simple rules of care. Do not forget about prevention, especially if you sow unfamiliar material.