What type of worms is the onion nematode, and how to fight it
The nematode is a dangerous pest that inhibits the development of plants and leads to their death. This tiny worm causes great damage to both private gardens and large farms.
Onion nematode causes rotting of onion heads, death of the root system and stems. Infected crops become unfit for consumption. From the article you will learn what the stem nematode of onions and garlic is and how to fight it.
What is onion nematode?
The nematode causes damage not only to onion beds. This pest is dangerous for parsley, tomatoes, and radishes. How to recognize it?
Description and characteristics
The onion-garlic nematode is a white thread-like worm. The length of the pest is 1-1.5 mm, and the thickness is 0.05 mm.
In the front part of the body there is a sharp, needle-shaped organ with which the nematode sucks out the cell juices of plants. The back of the body is pointed. Females are larger than males.
The larvae differ from mature individuals by having an inferior reproductive system and miniature size - only 0.3 mm in length. The eggs of the parasite are absolutely tiny -70×30 microns.
Attention. On dry onion scales, the parasite remains viable for more than two years, and in dried, infected garlic - up to five years.
The worm overwinters in onion heads and cloves of garlic, as well as in soil and seed material. Distributed everywhere. In Russia it is found mainly in heavy soils.
Peculiarities
What type of worm is a nematode? The pest is a large family of parasitic roundworms. There have recently been discussions about the species identity of the worm. Previously, onion stem nematode and potato were classified as one species. However, then scientists found that the food items of these parasites are different, which causes some physiological differences.
Soil-dwelling nematodes patiently wait for a host plant to appear. They can survive without a food source for up to 18 months. In search of food, the worms rise from a depth of 1.5 m. Adults infect stems, leaves and bulbs.
Important. A massive invasion leads to the destruction of that part of the plant in which the parasites have settled. They then leave the dead tissue and move to the next plant.
The pest is amazingly resilient. Nematode eggs and larvae can withstand temperatures down to -80°C for 20 minutes. Therefore, frosty winters have little effect on the number of pests living in the soil.
When the humidity drops, the worms enter suspended animation, in which they can remain for up to 20 years.
Breeding period
The onion nematode reproduces inside leaves and bulbs by laying eggs. The eggs hatch into larvae that go through four stages of development.
The life cycle of the parasite takes about 45 days. Thus, during one gardening season, three or four generations have time to grow.
Thousands of individuals live on one plant at the same time. Sexually mature individuals mate directly in the plant host. Each female lays up to 400 eggs (8-10 eggs per day).
The optimal temperature for parasite reproduction is +13…+18°C.But even in the range from +1°C to +35°C, the reproduction of worms does not stop.
The larvae emerge from the eggs after a few days. Young individuals begin to actively feed, devouring plant tissue. Grown larvae are able to move to neighboring plants.
Eating habits
The nematode pierces the plant tissue with its stylet - a pointed organ at the front of the body - and sucks out the cell juices. Parasite enzymes released during feeding inhibit the development of greens and onions.
After some time, the plant most densely populated by parasites dies. And nematodes, sensitive to the quality of nutrition, leave dead tissue and move to neighboring plants.
Symptoms of onion nematode infection
Infection is indicated by symptoms such as underdevelopment and deformation of leaves, their yellowing and drying, loosening of the bulb, and its cracking. The bottom becomes rotten, falls off, and the bulb is completely destroyed.
In an onion that has been subjected to early infection by a nematode, the first leaf that appears is curved and swollen; later, as it grows, the curvature of the leaves and thickenings, located mainly in their lower parts, become more and more noticeable.
If the seedlings were infected at a later stage of development, the diseased plants may be almost indistinguishable from healthy ones, but white spots often appear on the bulbs.
Cutting these bulbs open reveals granular, loose, fleshy scales that are unevenly thickened. In the initial stage of the lesion they are white, and later acquire a gray or brown color. Cavities form between the inner scales, the bulb becomes soft to the touch, and its bottom and sides may crack.
If onion nematode colonizes garlic, its stem thickens and cracks. The leaves curl, bend in waves, dry out and turn yellow. The bulb loosens and becomes damp to the touch, its bottom may become rotten and fall off.
What is the danger of onion and stem nematodes?
The onion nematode invasion threatens to significantly reduce the quantity and quality of the crop.
The parasite carries many diseases, which in turn slow down the growth of plants or lead to their death. Worms damage the root system, compromising its integrity. This is how pathogenic microorganisms - viruses and bacteria - penetrate inside the plants.
In addition, plants infected with a nematode have reduced resistance to other parasites, such as hoverflies, mites, and onion flies.
Diseases of onion and garlic caused by nematodes reach their greatest development by the time of harvest. Onion heads infected with worms begin to rot after storage. If there is high humidity in the room, worms are able to move from infected heads to healthy neighboring ones.
Methods of pest control
Pest control is carried out in several ways:
- compliance with the rules crop rotation – crops affected by the nematode are returned to their original place no earlier than after 4-5 years;
- selection of healthy material for sowing – sevok before planting, carefully inspect, removing specimens with signs of onion nematode infection;
- maintaining optimal storage conditions - low temperature (0...+2˚С) and low humidity (50-60%) in the storage reduce the activity of the pest.
In addition, among the methods of combating nematodes, folk remedies and chemicals are distinguished.
Traditional methods
The use of traditional methods in the fight against onion nematode is ineffective. These means can destroy only a small part of the adult population.
Summer residents practice the following methods:
- Treatment of planting material with hot water. The sets and seeds are soaked for an hour in hot water at a temperature of 45˚C. Then they are dried and planted in the soil.
- Disinfection of seed material in an infusion of wood ash for two hours. After soaking, the seeds or sets are thoroughly dried.
- Warming up the seeds at a temperature of 42-45˚C the day before landings.
- Treatment seed in a solution of potassium permanganate, formalin or 1% saline solution - leave for 30 minutes.
Chemicals
Chemical preparations show maximum effectiveness.
One of the popular chemicals is called “Percalcite”. This is an oxygen-containing preparation that destroys nematode cysts with eggs and larvae in the soil.
Use the product in dry weather. The drug is scattered over the sown area 5-10 days before sowing. For one square meter use 200-300 g of the substance. Then the preparation is sealed with a shovel or rake to a depth of 10-15 cm.
Another effective remedy is carbamide (urea). It is applied 30 days before sowing at the rate of 100 g per square meter. m.
Preventive measures
One of the most reliable ways to protect crops from infection is prevention. Regular use of preventive measures reduces the risk of onion nematode invasion to a minimum.
The following methods are used as prevention:
- regularly changing the place where the crop is planted - alternating plants, among other things, improves soil fertility;
- treatment of seed material before planting with high temperature or chemicals;
- destruction of plant residues after harvesting - special attention is paid to the destruction of infected plants and weeds;
- regular application of inorganic fertilizers.
Nematode-resistant varieties
Selection has not yet developed onion varieties that are absolutely resistant to onion nematode damage. But there are a number of varieties that are less susceptible to pest damage. These include Bamberger, Exhibition, Centurion.
Among those particularly susceptible to infection are Bessonovsky, Arzamassky, and Kaba.
Conclusion
Onion nematode is a parasite that reduces the quality and quantity of onion yield. The pest is tenacious and can wait for a host plant in the soil or seed for a long time. Therefore, when growing onions, special attention is paid to measures to prevent infection with nematodes.
If a pest is detected, chemicals are used, since folk remedies are ineffective.