Pests Of Onions And Garlic During The Growing Season

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

There is no beast worse than a fly

Many dangerous pests are known that not only destroy a significant part of the onion and garlic harvest during the growing season, but also greatly reduce its quality and safety. Some harmful objects harm the underground organs of these crops - onion fly, onion hoverfly, onion (root) mite, stem nematode, others - to the leaves and inflorescences - onion lurker, onion leaf beetle, tobacco (onion) thrips.

Often, owners of household plots and garden plots, due to ignorance of these pests, do not carry out any protective measures, and as a result, they often lose a significant part of the crop. It happens that he dies completely.

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The onion fly (it has an ash-gray body with a greenish tinge on the back 6-8 mm long) flies out in the second half of May. The beginning of the summer of the pest in early and warm spring occurs during the flowering of cherry and dandelion, massive years and the laying of eggs by females - during the flowering of lilacs.

The onion fly lays white oblong eggs (about 1 mm long) in groups of 5-20 on dry scales of bulbs and leaf bases or under lumps of soil next to plants. A week later, worm-like larvae hatch from the eggs, narrowed towards the front of the larva, which are drilled into the juicy tissue of the bulbs (usually from the bottom) and feed inside the bulb. More often they concentrate in the lower part, making passages in juicy scales, causing rotting of the bulb, especially quickly in wet weather. It is interesting that individuals hatching from the same clutch, as a rule, stick together, eating up a common cavity.

As a result of such damage, the leaves lose their turgor, wither, acquiring a yellowish-gray color, and later dry up. Bulbs damaged by an onion fly soften and rot, since the larvae of the pest are carriers of bacteria that cause wet rot. After feeding, the larvae go into the soil in 2-3 weeks, pupate, and after another 2-3 weeks flies of a new generation appear: the laying of a new series of eggs and the appearance of new larvae are repeated, which again harm the onion plantings. After pupation, these larvae hibernate in the soil at a depth of 12-20 cm.

If in the middle lane the onion fly gives two generations over the summer, then in the conditions of the Northwest, only one is usually noted, although, given the warm autumn (September and part of October), the second is also possible here. The most dangerous pest is with an early and friendly flight. The onion fly is most harmful on light sandy loam and loamy soils with permanent cultivation of crops, which often happens on personal plots. Onions sown with seeds, as well as sown at a later date due to the fact that the plants do not have time to grow and get stronger, suffer greatly. Because of this, by the time the pest appears on the plantings, the plants are in the most vulnerable to damage phase of seedlings (2-3 leaves). Along with onions, fly also actively damages batun onions, sometimes leeks, shallots, chives and garlic.

Onion hoverfly - a fly larger than the previous pest (6-9 mm long), bronze-green in color. After emergence in mid-June (sometimes the emergence coincides with the flowering of a dandelion), females feed on nectar on flower crops for some time. The fly often flies in a vicious circle; for landing, it chooses well-lit open areas of landings. Onion hover eggs are laid directly on the bulb (behind the outer covering scales or in the neck) or next to it directly on the soil surface.

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A stimulus for an active clutch of eggs (40-55 pieces) 1 mm in size can be the specific smell of mechanically damaged or diseased plants. The fly flies all day long. A week later, dirty yellow larvae emerge from the eggs. In the same clutch, they hatch almost simultaneously and immediately try to penetrate into the bulb. A characteristic difference of the larvae of the onion hoverfly is the presence of a short process in the form of a brown tube on the back of the wrinkled body.

These larvae feed on the inside of the bulbs, turning the inside into a black rotting mass. It takes them up to a month to feed, this generation of larvae is very harmful to onions, by its actions it leads to the formation of 1-2 arrows. After that, the larvae pupate in the upper layers of the soil. A new generation of hoverflies appears in late July - early August, it also harms onion plantings. The larvae overwinter inside the bulbs. In addition to onions and garlic, the pest also affects the bulbs of daffodil, tulip and gladiolus.

The onion (root) mite has an oval, thick, whitish-vitreous body (0.7-1.1 mm in size), brown legs and mouth parts, which can only be seen with a magnifying glass. Its harmful effect is often the reason for the low yield of onions.

This is sometimes a surprise to vegetable growers, who suddenly discover, when harvesting, a lot of soft, decaying bulbs, covered with brownish dust on the outside. The mite is harmful during the growing season and during storage, populating mainly bulbs that are diseased or damaged by other pests (onion flies and hoverflies, nematodes). This pest enters the site with infected planting material, from which it can move to neighboring unpopulated bulbs.

But sometimes it settles in soil with some previous culture. Then it penetrates from the soil into the bulbs, most often from the bottom, which becomes rotten and falls off. Through the bottom, the pests enter and feed on juicy fleshy scales, while the damaged bulbs rot (fungi and bacteria contribute to the decay process). Females lay eggs in the bulbs (fertility is up to 800 pieces), of which in 1-2 weeks, depending on weather conditions, larvae hatch, which feed on plant sap. The full development cycle of this pest is a month.

The mite overwinters in bulbs, in the soil, in post-harvest residues, in greenhouses and storage facilities. It should be noted that mites are heat-loving and moisture-loving organisms, multiplying especially intensively at temperatures above 13 ° C and air humidity above 70%. And if an air humidity of 70% or more is noted in the room, the mites begin to actively multiply, but when it decreases, the development of the pest stops. Deterioration of living conditions or lack of food leads to the emergence of a very persistent form of the pest, called "hypopus": in it, ticks can exist for a long time without eating.

Adult stem nematodes are small (1-1.5 mm long) filamentous whitish worms that pierce the cells of leaves and bulbs, sucking the juice out of them. Females lay eggs in plant tissue, from which larvae hatch, feeding similarly to adults. Seedlings damaged by an adult nematode or its larvae swell, bend and, as a rule, die. Onion sets have curved and thickened leaves at the bottom. The juicy scales of the damaged bulb acquire a grayish and then brownish tint, loosely adjoin each other, which makes it seem soft to the touch.

The bottom of a bulb damaged by nematodes usually cracks. As a rule, nematodes either carry rot pathogens themselves, or contribute to the settlement of these microorganisms when they mechanically damage the tissue of the bulb, therefore, such bulbs usually rot during storage. Nematodes overwinter in bulbs and soil; in dry plant residues they are able to remain viable (in anabiotic state) for up to 4-5 years and are activated when exposed to a humid environment. In addition to onions and garlic, they also damage plants in a number of other families.

The onion lurker is a small (2-3 mm long) black beetle with whitish scales on its body and a downward-bent proboscis - a weevil. Emerging from its wintering grounds, it first feeds on sprouted old bulbs remaining in the soil, or on perennial types of onions - on a batun onion, chives, and multi-tiered onions. This usually occurs at the end of April - beginning of May. The female gnaws through the leaves almost dotted holes of white light, where she lays eggs. After 1-2 weeks (depending on weather conditions), yellowish legless larvae hatch from the eggs, which begin to scrape out the inner juicy pulp of the leaf without damaging the upper shell.

Such leaves, with well-distinguishable whitish longitudinal stripes, turn yellow quickly, starting from the top, and, as a rule, dry out. On one leaf, sometimes there are 8-10 larvae. Having finished feeding, after 2-3 weeks they go into the soil for pupation, so that in early July they appear in the form of young beetles, which begin to actively damage the leaves of plants, and are also able to gnaw the pedicels of the testes, thereby reducing the yield of seeds. Beetles hibernate on weeds, not far away from the plots, and it happens - right on its territory.

The onion beetle is a beetle with an elongated oval (7-8 mm) body (it is reddish-orange above, black below) and red legs - appears in early May. Initially, females feed on wild and domestic lily crops. If you disturb the beetle, it instantly falls to the ground. Then the females move to onion plants, laying orange eggs in groups of 10-20 on the underside of the leaves. Having hatched, the larvae (of a dirty yellow color with a black head) eat holes in the onion leaves, penetrate into them.

After 2-3 weeks, the larvae pupate in the soil, and at the beginning of July the beetles of the next generation begin to emerge, which then hibernate in the surface layer of the soil (often on weeds). In addition to onions, the onion beetle damages the leaves of garlic, onion and chives, as well as lily of the valley and many liliaceae. Having hatched, the larvae can very quickly skeletonize the leaves and petals of lilies, which will completely lose their decorative effect.

Tobacco (onion) thrips is a very small insect (up to 0.8-0.9 mm in size) with a thin elongated body of light yellow or brown color. It has two pairs of wings (narrow with a fringe of hairs along the edges). Thrips usually appear in June, settle in the axils of onion leaves (on the testes - in the inflorescences), actively sucking the sap from the plants. At the first stage, damage from thrips looks like whitish spots, later the leaves bend, turn yellow and dry out.

Upon close examination of such leaves, you can find small black dots on them, which are the excrement of these pests. Females lay eggs under the skin of the leaf. A week later, larvae appear from them, which feed in the same way as adults. The transformation into adult insects occurs in 3-4 weeks: they fly away and fall on other plant species. In addition to onions and garlic, the pest also damages tobacco, cabbage and cucumber. It hibernates on plant debris, in the upper soil layer, under dry scales of bulbs. If onions and garlic are stored in an apartment in winter, where the temperature is maintained at 18 … 22? C, the pest continues to feed and reproduce.

Pest control of onions and garlic

In the fight against these pests, it is important to observe a set of agrotechnical techniques. With a crop rotation, onions and garlic are returned to their original place no earlier than after 3-4 years. All types of onions and garlic are not planted nearby to avoid the spread of harmful organisms. Cucumber and tomato are considered good predecessors of these crops. The landing site is chosen on an area with good ventilation.

Also recommended for pest control:

• early sowing and planting dates;
• timely (during the period of mass pupation of pest larvae) inter-row treatments;
• top dressing and moderate watering, providing amicable growth of green mass;
• collection and destruction of plant residues after harvesting;
• deep digging of the soil.

For example, the amount of onion beetle, which often hibernates in lily plantings, reduces soil digging, which is carried out carefully so as not to damage the flower bulbs. When these beetles are found on flowers, they are carefully collected and destroyed. With a high number of pests, planting lilies are sprayed with phytoverm.

Damage from pests (especially from onion flies) is seriously reduced if onion crops are sown early: by the time the pests fly out, the seedlings become strong.

A mandatory agricultural practice is to carry out 4-5 inter-row treatments during the growing season, which maintain the top layer of the soil in a loose state and prevent the growth of weeds. It is important to use the recommended doses of fertilizers and not to chase the growth of green mass due to nitrogen or organic fertilizers. To scare off onion flies and onion hoverflies, some gardeners sprinkle the soil with repellent agents - wood ash, tobacco or tobacco dust with sand (1: 1), repeating this technique 2-3 times every week.

Mulching the soil near the plants with peat is also effective. It is recommended to place beds of onions or garlic next to carrot plantings: it is believed that onion phytoncides scare away carrot flies, and carrot phytoncides - onions. During the growing season, they fight against pathogens that weaken plants. When growing turnip onions intended for long-term storage, watering is stopped a month before harvesting.

When using green onions on a feather, the use of a chemical method against these pests is undesirable. In addition, many of these pests during the growing season of plants lead a hidden lifestyle (inside the leaves), so the chemical effect on them is limited.

Onions and garlic are harvested in dry weather after the formation of bulbs, dried in the area until the leaves dry out and dry covering scales form. After drying, the leaves are cut off, the bulbs are heated at a temperature of 35 … 37 ° C for 5-7 days and placed in storage. Sprinkle onion sets with dry chalk.

Before planting, the bulbs are sorted out, rejecting sick and damaged ones. Some practitioners use a rather laborious, but quite effective thermal method to disinfect the bulbs from stem nematodes and thrips by immersing them in water at a temperature of 45 … 46 ° C for 10-15 minutes. If a higher temperature of water is used, then the exposure time is reduced (6-8 minutes at 50 … 52 ° C or 3-5 minutes at 55 … 57 ° C), then cooled with cold water. Other gardeners practice healing onions and garlic from these pests by soaking the bulbs in water (at 16 … 18 ° C) for three days.