Beet nematode - a secret pest on agricultural fields

The nematode family is a dangerous parasite of crops. They provoke the occurrence of sugar beet diseases. One of the most common is heteroderosis. In affected plants, there is a slowdown in the growth of the root crop, lethargy, and a complete death of the culture. Beet nematode causes significant damage to agriculture. Representatives of this family are found everywhere. In addition to their own negative effects, they provoke the appearance of viral and bacteriological infections.

Parasite morphology

The body of roundworms is covered with a smooth or annular cuticle. They lack the circulatory and respiratory systems. In beet nematode, pronounced sexual dimorphism is observed:

Female

The size of the female is 0.8-1.3 mm long and 0.2-0.8 mm wide. She has a lemon-shaped body. At the initial stage, the female is white, then becomes yellow and brown. The head is small, the neck is short, expanding at the base. Head cone smaller than vulvar. The nematode has a gelatinous egg sac. It contains most of the eggs. Inside the body are long swirling ovaries. The outer cuticle of the female is covered with many grooves.

Male

Males have a length of 1-1.3 mm. He has a transparent elongated body. On the front side there is a small protrusion on which the mouth opening is located. A spike peeps out of the worm's mouth. At the rear end are two needles that are pulled into the cesspool. This organ is used in mating. The life span of the male is about a month, he dies after the fertilization of the female.

Information. Nematodes were first found on the roots of sugar beets. They were discovered by the botanist Mine. This species was named after the scientist Heterodera Schachtii.

In its development, parasites go through several stages:

• barrel-shaped egg, size 0.1 mm;
• cyst - the shell of a dead female, filled with eggs and larvae of the first age;
• larvae of the second to fourth age;
• adults.

In any soil there are brown cysts of nematodes, in which hundreds of parasites are waiting in the wings. When a sugar beet root is nearby, the larvae catch the substances secreted by them and begin to move. They gnaw through the cyst membrane and rush to the plant. Using a stylet, the larva drills the surface of the root. Inside the plant, it moves, dissolving the cells with special enzymes. The parasite is purposefully selected to the channels for transporting nutrients. With the help of secreted secrets, the larva changes the structure of sugar beet root cells, making it most suitable for its nutrition. With multiple offspring of nematodes, beets lose a large amount of nutrients.

Drunk larvae begin to develop into male and female individuals. All molting processes take place inside one swollen shell. Only upon reaching the adult stage do males leave it. They come out of the vegetable in the soil. Males no longer eat.Females do not leave the root; it constantly eats and grows. After several molts, they significantly increase in size and break the beet shell with their backs. The female body takes the form of a lemon.

Attention. Adult females are visible on the roots of sugar beets without optical magnification. They look like white lumps.

The spread zone of beet nematode covers the whole of Europe, Russia, they are found in the fields of North America and Australia. Roundworms of the species Heterodera Schachtii have settled in all temperate regions of the world.

Nematode reproduction

Roundworms lead a secretive and sedentary lifestyle, but multiply rapidly. Females secrete pheromones to attract males. The males in the soil creep up to the female. They inject sperm into it with a special organ, spicule. After mating, the process of egg formation begins. One female is able to lay 200-300 eggs. During this period, she eats especially intensively. Part of the eggs is laid in an egg bag. Larvae of them appear soon. The female dies and turns into a strong brown cyst.

Under favorable conditions, beet nematode produces several generations. The development of one generation takes one to two months. The most suitable for nematodes is a temperature of 25-30⁰. The larva of the second age, having penetrated the root crop, makes moves 1-2 cm, then proceeds to feeding. At this stage, they do not have gender differences. The offspring leaves the cyst at a steady temperature of 10⁰. The speed of their movement depends on the structure and soil moisture. Not all larvae leave the cyst, about 50% remain to winter under the protection of the hard shell. They start feeding next spring.

Attention. In the Central regions of Russia during the growing season 4-5 generations of nematodes are replaced, in the Non-Chernozem region 2-3.

The presence of a cyst phase in the development cycle ensures the survival of a large number of offspring. Their passive resettlement occurs with infected seed material, during mechanical processing of the soil, using wind and water flows. In the fields, mass reproduction of beet nematode occurs due to non-compliance with the recommended rotation rotation.

Attention. Within the cysts, parasites are protected from predators and adverse conditions. They are able to maintain viability from 1 year to 10 years.

Nematode Harmfulness

Beet nematode is considered the cause of "beet fatigue" of the soil. Their effects are not always detected. In some cases, the deterioration of the condition of the culture is attributed to excessive humidity or drought, as well as the action of herbicides. A high concentration of parasites leads to the fact that 70% of vegetables remain underdeveloped, even with timely feeding. Productivity in such fields is reduced by 2-3 times from the planned indicators. In a damaged root crop, the amount of sugar decreases.

Attention. If the number of nematodes exceeds the economic threshold of harmfulness, then beets cannot be sown in this field. It is worth abandoning the planting of other cults on which worms parasitize - canola, radish, mustard.

The spread of parasites occurs foci. The first sign of damage is lethargy of leaves on a sunny day. The extreme leaves begin to turn yellow and die off soon. Attack on crops occurs at an early stage in the development of sugar beets. At this stage, culture is particularly vulnerable. Its growth is slowed down, there are many additional roots, causing beetroot. On additional branches that arose in the feeding places of the pest, females and cysts are sitting.

A disease of the culture caused by beet cyst-forming nematode is called heteroderosis. It poses the greatest danger during a drought. The pathological effect of the larvae is created using digestive enzymes introduced into the structure of the plant. Depleted withering crops in the foci of infection are often affected by fungi and rot.The harmfulness of the nematode depends on its amount in the soil. A high level of threat, which requires the use of chemicals, is 200 larvae per 100 cm³ land.

Gall nematodes rarely formed on beets. Outwardly, the appearance of a parasitic organism is completely invisible. The tops of the crop remain green. In the underground part around the central root, many galls are formed on the lateral processes, in which the worms are located. Through additional measles, they take nutrients from the root crop. Beets lag behind in development, lose their presentation, poorly stored.

After harvesting, many cysts with larvae remain in the soil on the remains of the root. They are ready to continue infection at the next sowing.

Ways to deal with the nematode

The microscopic dimensions of the pest, the delayed manifestation of signs of its presence and rapid reproduction complicate the protection of sugar beets. In order to competently organize a set of measures to destroy the parasite, it is necessary to conduct monitoring. For this autumn, after harvesting beets, soil samples are taken. Samples are taken on two diagonals of the plot, to a depth of 20 cm. Samples are sent to the laboratory, where the number of cysts and larvae are counted with a microscope.

Tip. Marigolds help fight a nematode in a private area. The root system of these flowers repels the parasite larvae. Pests avoid areas where marigolds grow.

Control measures include:

1. The crop rotation method with the inclusion of crops not affected by nematodes is highly effective. These include corn, barley, wheat, clover. Sugar beets in the infected field are planted no earlier than after 4-5 years. For complete disinfection, up to 9 crop rotations will be required. During this time, it is necessary to alternate the crops of cereals and legumes.
2. Weeds must be removed; special attention should be paid to plants of the cows and cruciferous family. Nematodes are able to feed on them in the absence of the main host.
3. Fields of sugar beets are dug in ditches, on the bottom of which lime is poured.
4. Waste is disinfected during beet processing.
5. Planting material, mechanisms and soil are treated with systemic nematicides. Preparations are applied after harvesting or in the spring, a month before planting.