One of the most dangerous plant pests are nematodes (roundworms). They are microscopic in size, live in roots, stems, leaves and even fruits, multiply very quickly. A great threat to plants is created by gall nematodes - pests that live in their roots. Penetrating into tissues, parasites contribute to the formation of growths and swellings (galls) in them, hence their name. What it is and how to deal with them will be discussed in the article.
In nature, there are about thirty species of these worms. Some of them affect plants, others - animals, and still others - humans. Further, we will only talk about root-knot nematodes parasitizing in the roots of plants:
- Male nematodes are mobile, in contrast to the spindle-shaped immobile females. Their body is worm-shaped, 0.5–2 mm long, narrowed at the front and rounded at the back.
- The larvae resemble the shape of the male, but are smaller. The back of the body is more transparent and pointed.
- Eggs- microscopic, white. The female lays them in the so-called egg sacs, consisting of a gelatinous film. One such bag contains a huge amount of them.
At the end of the front part of root-knot nematodes (photo in the article) there is a mouth opening, inside of which there is a rigid needle called a stylet. With the help of this apparatus, they pierce the root of the plant and suck out the juices. Worms have a small head, movable lips and tiny eyes. The outside of the body is covered with an impenetrable but flexible cuticle that is highly resistant to chemicals.
Biology of roundworms
They reproduce in two ways:
- The female is on the surface of the root and lays her eggs in a bag, the larvae from which first enter the soil, and then make their way into the root system of the host plant, after which it becomes infected.
- The female is completely in the tissues of the root and lays eggs inside it. The hatched larvae move along the tissues of the root and settle in it for nutrition and development. They are no longer biologically protected.
It should be noted that the larvae from the roots, under favorable conditions, are able to move through all the organs of the plant.
Root nematode attack
The most suitable conditions for their reproduction are high soil moisture and air temperatures above 18 degrees. The period of formation of the root gall nematode is approximatelymonth. It can reproduce up to six generations per year. Plants affected by pests have the following characteristics:
- oppressed look;
- leaf curling;
- stop growth;
- yellow gall formation;
- growth of many threadlike roots (root beard).
It is very important to distinguish the galls of a diseased plant from natural white thickenings that retain moisture.
Where does the root-knot nematode come from
Infection with a nematode occurs through the soil and planting material. But it is entirely possible to introduce tiny parasites using contaminated implements, pots, and even dripping water from a damaged plant when watering.
Nematodes can be found not only in the garden plot, but also in the forest, compost and humus. And even purchased soil using greenhouse raw soil can contain them.
Tiny worms have a terrible voracity and fertility. They quickly and in large quantities accumulate in the soil, especially when the crop is planted in one place. Most gall nematodes are found on cucumbers and tomatoes. Parasites, creating small thickenings in the roots, lay eggs, from which larvae emerge, devouring everything around them. Eating the roots, the worms do not allow the cucumber to develop, depriving it of the opportunity to eat normally. The roots of the plant affected by the nematode become watery, with thickenings of a brownish hue. Branches weaken, leaves falland cucumbers are dying.
Difficulties lie in the fact that the pest is very difficult to detect at an early stage of development due to its small size. For prevention, one must not forget about crop rotation, changing the cultivation of crops on the site annually. Where these parasites appeared, plant garlic or cabbage instead of cucumbers. Nematodes cannot tolerate these plants.
Open ground nematodes
Two types of root-knot nematodes are observed in the open field in temperate European part:
- Birch - settles only on birch roots and does not pose a particular danger.
- Northern - lives in legumes, umbrella, nightshade, ranunculus and Compositae crops. Although the pest infects a huge number of plants, it does not pose a big threat to annuals. This species has only one generation a year and does not have time to settle in the roots of the plant to greatly weaken it.
Soon we should expect a new parasite on the territory of our country - the Colombian root-knot nematode. It has already been brought to Europe, and it successfully harms carrots, potatoes, beets, peas and many other crops in open and closed ground. As a result of damage, the proportion of tubers decreases, and the yield decreases. Losses reach up to 80%. It hibernates in the roots of cultivated plants and weeds, and in the stage of eggs it is also in the soil. This parasite reproduces both sexually and asexually. Life cycle lasts up to fourweeks.
Nematodes that are absent in Russia
There are four types of these pests that cause plant diseases, but are not yet available in Russia. These include: Colombian, root, false Colombian and false gallic. Countries from which they can be imported are Ecuador, America, Mexico, Chile.
One of the most dangerous and polyphagous is the root. The exact range of its host plants has not yet been fully identified, but it is noted that the pest affects economically important crops: beans, soybeans, eggplants, cucumbers, watermelons and tomatoes.
No less dangerous is the false root-knot nematode. Its main hosts are potatoes and sugar beets. Infection with this species is possible through planting material (rhizomes, tubers) and soil. Worms of this genus form galls. They are most noticeable on sugar beet, from the thickenings of which small numerous roots emerge. Symptoms of the disease appear on the fifth day after infection.
How to fight?
To combat the gall nematode, the following means are used:
- Chemical preparations are the most effective: Rogor, Nemafos, Bi-58, Dimethoat. According to the instructions, the substance is dissolved, and the soil is treated with the resulting mixture. This procedure is carried out several times a season, because poisons only kill adults.
- Biological agents. Such substances consist of natural components, therefore they are not harmful to plants and humans. Often use "Nematofagin". Before use, read the instructions and strictly follow them.instructions.
- Heat treatment. The plant is removed from the soil, part of the heavily affected roots are cut off, where galls have formed. The rhizome is dipped in water with a temperature of 50 degrees for five minutes. The soil is replaced with another one that has a loose composition, adding an anti-nematode drug to it.
When severely damaged, the plant is simply burned so that the pests do not find another victim.
Detecting and getting rid of nematodes is very difficult, so it is best to take preventive measures and prevent the appearance of these parasites. For this you need:
- carefully carry out autumn tillage;
- destroy weeds in time;
- do not bring plants with a closed root system from botanical gardens, greenhouses and shops into greenhouses;
- clean up fallen leaves;
- observe crop rotation;
- loosen the soil regularly;
- fertilize the soil with organic matter;
- carry out periodically abundant irrigation of the land, followed by drying;
- try not to overmoisten the soil.
One of the modern ways to protect greenhouses from pests is the use of sulfur bombs.
Parasites living in the roots of plants are dangerous pests that can be difficult to detect. The main manifestations of the disease are expansions and swellings that appear on the root system. Having identified such neoplasms,conduct microscopic examinations, because they are not always provoked by the presence of nematodes.