At present, helminthiases of plants caused by roundworms (nematodes) are a serious problem for agricultural production. World losses of crop production from nematodes averaged 7-10%, with severe infection, agricultural producers receive less than 80% of the crop.
Potatoes are exposed to several types of nematodes. Among them are stem (Ditylenchus destructor), northern gallic (Meloidogyne hapla Chitwood), pale (Globodera pallida Stone) and golden (Globodera rostochiensis). The stem (tuber) nematode damages the underground parts of plants (both during the growing season and during storage), causing a dangerous disease of ditylenchiasis. In the tuber tissues under the peel small white spots are formed with holes in the very middle. Affected areas become soft and are detected when palpating. Affected tubers wrinkle and rot. Most often, plant infection occurs in the field, and in the conditions of the storage, the disease begins to progress.
No less harmful is the northern gall nematode, which parasitizes on the roots and tubers of potatoes and contributes to the development of meloidoginosis. On the roots of Dietilenchosis, caused by potato nematode plants, thickenings (galls) are formed. The pest prevents access to the stems of plants of water and nutrients, which leads to a decrease in the quantity and quality of the crop. The pale potato nematode is also capable of causing economically significant loss of potato yield. The pest lives in a cold and temperate climate, is widespread in European countries, and is subject to external quarantine.
CAUTION - CYST
One of the most serious pests is the cyst-forming golden potato nematode, which causes a dangerous disease - potato globoderosis (other plants of the Solanaceae family are also susceptible to it, but to a lesser extent).
Golden potato nematode is included in the list of pests of quarantine significance for the Russian Federation.
HOW IS THE NEMATODE CYST FORMED?
Female cyst nematodes form cysts with eggs on potato roots. After planting potatoes in the spring, the invasive larvae emerge from the cysts under the influence of root exudates for 3-6 weeks and infect the roots. The larva enters the root through the root cap and for several days moves along the root conduction system, after which it stops and forms a feeding zone of several giant cells. Depending on the soil temperature, females and males are formed from the larvae within 1,5-2 months. A few days after copulation, the female begins to accumulate eggs in the body cavity. Young females of white color by autumn acquire a golden color and in this state go to winter. Towards the end of life, the female's body is completely filled with eggs, turning into a kind of capsule, covered with a dense shell - a cyst.
Cysts dwell in the soil, infecting the roots of plant crops during the subsequent growing cycle, and can be stored for a long time (about 10 years) even without the presence of the host plant.
It is difficult to deal with cysts - traditional methods (steaming the topsoil and crop rotation) are ineffective, they are almost not exposed to chemicals.
Currently, many scientists and agricultural practitioners are betting on the possibilities of biological preparations (based on predatory fungi), the principle of which is based on natural “predatory” mechanisms. Such drugs, in addition to being effective in solving the main problem, have additional advantages: they are not toxic, do not cause addiction in the pest.
HOW TO DETECT NEMATODE
The nematoda is a tiny round worm (0,5-1 mm in size), it is difficult to see it with the naked eye. But an infected plant can be identified by a number of distinctive features. The first features appear already 3-4 weeks after the emergence of seedlings: the plants lag behind in growth, begin to turn yellow prematurely (mainly from the lower tier), they have a smaller number of stems, the leaves curl.
Flowering is usually absent or very poor. Heavily infested bushes die long before harvest, producing very small tubers or none at all. The root system of infected plants is brown, smaller than normal and has many lateral roots. By mid-July, golden balls are formed on the roots of potato plants - the only direct marker for the detection of golden potato nematode.
For a more accurate diagnosis, methods for determining the invasive load have been developed and described in detail in the professional literature. However, in the field, most of them - due to the need to use special equipment - are not available.
Therefore, farmers are urged to do a soil analysis every year for the presence of nematodes. The sooner a problem is discovered, the easier it will be to get rid of it.
NEMATODA INFECTION
The source of the nematode distribution is infected potato tubers and infected soil (during harvesting, cysts fall off the roots and remain in the soil). It is cysts that serve as the main source of infection for all new areas, since they can be transferred on seed potatoes, with tools and even on shoes.
The main ways of infection:
• when planting infected tubers;
• when storing infected tubers together with healthy ones in conditions of high humidity;
• when using an untreated tool that came into contact with contaminated soil;
• when tubers are planted in soil where infected potatoes were previously grown.
The most favorable conditions for the golden potato nematode are created in areas where potatoes are grown from year to year, without observing crop rotation rules.
DISTRIBUTION IN RUSSIA
According to the Rosselkhoznadzor, as of January 1, 2018, the area of identified foci of the distribution of golden potato nematodes in Russia is about 376 thousand hectares, and the area of quarantine phytosanitary zones for this pest exceeds 1 million hectares.
The distribution range of the golden potato nematode currently includes 64 regions of the country (including foci in the Urals, Siberia and the Far East), in 906 municipal regions.
The spread of golden potato nematodes adversely affects the development of potato farms and poses a significant threat to the country's food security.