Nematode is the enemy of the potato grower, "which can not be talked about." No one discusses suspicions about the possible infection of their fields or successful methods of struggle.
No one discusses suspicions about the possible infection of their fields or successful methods of combating a pest in a professional circle, with neighbors in the household. Perhaps that’s also why the topic with each year is becoming increasingly relevant. The editors of the magazine decided to contribute to correct the situation and highlight the most important, in our opinion, aspects of the issue.
We asked to tell one of the leading Russian experts in the field of phytoparasitology - the head of the Laboratory of Phytoparasitology of the Center for Parasitology of the Institute for Ecology and Evolution Institute . A.N.Severtsova RAS, Head of the Laboratory for the Diagnosis of Phytopathogenic Organisms of the All-Russian Research Institute of Phytopathology Mikhail Pridannikov.
ONE OF 30 thousand SPECIES
When it comes to the nematode, it is first necessary to clarify what kind of roundworms are being discussed. Currently, science knows more than 30 thousand species of parasitic and free-living nematodes, while experts suggest that in reality there are at least a million of them.
However, for the professional community of potato growers of interest are only those who are able to live on potatoes and cause significant harm to the culture. This is a pale potato nematode (lat. Pale Globodera),
Golden Potato Nematode (lat. Globodera rostochiensis) and stem (tuber) nematode (lat. Ditylenchus destructor) Pale potato nematode is an object of external quarantine; data on its detection on the territory of Russia has not yet been recorded.
But do not forget that almost all of this area is occupied by private gardens or farms of small farmers (up to 100 hectares). For large agricultural producers Globodera rostochiensis It does not pose a serious danger; if a pest is found in one of the fields, it is possible to exclude this area from crop rotation without much damage to the business.
A much greater threat is the stem nematode. For large agricultural enterprises Ditylenchus destructor today becomes problem number 1.
INVISIBLE AND VERY DANGEROUS
The stem nematode infects tubers and underground parts of the potato stem. On the terrestrial part, the signs of the disease are clearly not manifested, therefore, it is almost impossible to determine infection with Ditylenchus “by eye”. In this case, the formal signs of damage to the tubers (soft dark spots) are easily confused with the symptoms of fungal or bacterial rot. Even specialists can confidently talk about the presence of ditylench only after conducting a special analysis. But here there are certain difficulties. As a rule, damaged tubers and / or soil samples enter the laboratory. Often there are cases when in these samples a nematode is found under a microscope (as already mentioned, the number of species of this microscopic worm is more than 30 thousand), but far from always we are talking about harmful ditylenchus.
TO THE HISTORY OF THE QUESTION
The stem nematode is not a new guest on Russian lands; the pest was detected in the country at the beginning of the XNUMXth century. In Soviet times, the spread of the pest was controlled by phytosanitary services. Then about the problem forgot for a while.
First calls to the phytoparasitology laboratory for About ditylench we began to fix in 2014-15.
Lack of attention to stem nematode, capable of blaA favorable year for her to destroy up to 80% of the crop is explained simply: determining its presence on the field is not so simple.
Unfortunately, the qualifications of employees in different laboratories are not always high, and false diagnoses in these circumstances are not uncommon.
How to avoid a similar situation? Firstly, it is very responsible to approach the collection of material for analysis: to bring not only land, but also to find plant debris, parts of weeds - it is in them that the stem nematode prefers to settle. Secondly, at the slightest suspicion of the presence of a pest, samples should be taken to several laboratories. Research costs in any case will not be comparable with the cost of error.
We do not have accurate data on the extent of the spread of the pest in Russia. The stem nematode is not among the quarantine objects, therefore, no one conducts centralized studies (as in the case of the golden potato nematode). Based on the geography of requests to our laboratory, I can note that ditylenchiasis is found in almost all central regions of the country. The most problematic ones include the Nizhny Novgorod and Bryansk regions.
Over the Urals, cases of infection are also recorded, although so far we are talking about isolated episodes.
But let's not forget that the stem nematode is difficult to determine, and if the problem is still detected, it is not customary to talk about it.
IF THE PEST IS DETECTED
Most often, a massive lesion of ditylechomas is detected on the eve or already during harvesting. A typical case, when they examined the plantings in August, everything was fine, after two or three weeks they began to clean, and there was nothing left of the potato. The pest manifests itself most strongly under favorable conditions for it (it is humid, warm weather without sudden changes in temperature, moist soil). And here is another important point: a lot of farms are now switching to artificial watering, they should especially carefully monitor the presence of ditylench on their lands.
The amount of damage to the farm depends on the degree of damage to plants
The farmer has the right to realize everything that he managed to collect: the potato affected by ditylenchus is not destroyed.
But since the quality of such products is noticeably reduced, prices for it also have to be lowered. Heavily damaged product is taken away by starch factories.
Seed potatoes will have to be sorted several times before being sold. And of course, the producer will have to significantly reduce the class of material. In potato seeds of the "Elite" class (OS; ES; PP-1; SSE; SE; E) infection with ditylenchosis is not allowed, and in the seeds of the first and second reproductions (PC1 and PC2) up to 0,5% of infected tubers are allowed according to GOST.
We also note that the detection of the pest does not entail the imposition of any punitive sanctions on the economy. But the very fact of infection (even if the percentage is not critical) should be a signal to the farmer that the work in his farm is not perfect and you need to at least be more careful about the choice of suppliers of seed material (most often the stem nematode is imported with seeds) and be sure to check every imported batch.
The first thing to do before buying seeds is to carefully consider them. Just wash two buckets of potatoes and evaluate how the tubers look, whether they look like in appearance. It is very important to carry out this procedure in advance, at least a month before landing.
At the slightest doubt, the material must be sent for analysis. Even with a small percentage of infection with ditylenchiasis, planting should not be allowed, so as not to struggle for the purity of their lands for 5-7 years, constantly keeping the problem under control.
METHODS TO COMBAT
The fight against any type of parasitic nematode requires the development of a whole range of measures, taking into account the individual characteristics of each particular economy. And you always need to start with building a crop rotation. I will make a reservation right away that it is much more difficult to select the necessary list of cultures for infection with ditylenchus than for the defeat of globulose. The fact is that the golden potato nematode eats only potatoes. In order to get rid of it, for a sufficiently long period not to plant this culture in infected areas. It is not by chance that the stem nematode is called a destructor; it can live on about 40 species of cultivated plants and no less than a hundred wild ones.
Given this, experts recommend that at first leave areas infected with ditylenchus unseeded. Under conditions of pure steam, all plant residues decompose, and the number of pests decreases sharply. Ditylench also does not like cereal crops; it propagates inactive in them. Separately, it is worth mentioning the use of siderates. In the list of these crops, you can select the appropriate “candidates” for inclusion in the crop rotation. Take mustard, for example.
After smelling, this plant decomposes in the ground, releasing specific substances that are harmful to the nematode. But in order for the plant to fulfill its task, it is necessary to smell it at a strictly defined moment, upon reaching the optimal phase of development. Many prefer to wait until the seeds appear, and only then deal with the remaining green mass. As a result, agricultural producers hold an excellent event to improve the structure of the soil, but it has no effect on the nematode, since all active substances go into the seeds.
In the fight against ditylench (and any other phytopathogens), hygiene of production is also of great importance. It is necessary to regularly and thoroughly remove the dirt remaining on the equipment - on all machines that work in the fields and in warehouses. Imagine if a few dietilench tubers are spread, say, on a sorting table, ditylench will settle on the entire batch that will follow there. And to avoid large-scale infection is very simple - just rinse the surface. Even if you do not add fumigants, plain water will remove 99,9% of the question. Speaking of hygiene, it is necessary to pay attention to the complex issue of disposal of rotten products.
Where do the spoiled products get dumped most often? To the nearest ravine or ditch right at the vault. From there, all diseases and pests (including the nematode) remaining on these tubers are easily transferred to a healthy crop. The example becomes especially vivid if the water from the ravine flows into the local reservoir, from which the farm takes water for irrigation.
NON-MATERIAL RESISTANT VARIETIES
In modern catalogs of breeding and seed companies there are always varieties that are highly resistant to the nematode. You need to understand that in this case we are only talking about resistance to golden and pale nematodes, because it is determined genetically. There is simply no resistance to ditylench due to genes. This is a destructor.
Although to say that the pest equally perceives all varieties of potatoes is also incorrect. Researchers identify relatively stable (less affected, with a lesion volume of up to 10%) and highly affected varieties (primarily those that are processed).
But it is too early to build a coherent classification. Scientific papers on this subject, which appear from time to time, mainly reveal narrow aspects of how ditylenchiasis spreads in certain varieties, in certain climatic conditions, with a certain degree of infection. How the same varieties behave, but at different temperatures and with a different degree of infection, remains a question.
CHEMICAL AND BIOLOGICAL PROTECTION
Currently, only one nematicide is allowed in Russia - Vidat 5G. In the future, there should be more of them: in the portfolios of all major manufacturers of plant protection agents there are such drugs, and now concerns are making every effort to speed up the registration process.
As for biologics, in my opinion, in the fight against ditylech, they are still ineffective, and as a biologist, I am skeptical about their prospects. The developers have interesting ideas, but it is still hardly possible to defeat the epiphytotic infection with “biology”.
Let's draw an analogy: a person treats a serious illness with antibiotics, and then drinks vitamins to maintain overall immunity. Also here: chemistry is necessary to reduce the level of invasive infection to a minimum, and only then you can connect the "biology" to maintain soil health.
At the moment, ditylenkhoz can be called a serious problem for Russia, but still not a disaster. With certain efforts, each farm is able to drive the pest into the framework when it is present in the soil, but cannot harm the crop.
And in the foreseeable future, I think, we will come to the same regulations that are used today in Europe. In Holland, for example, all seed farms and enterprises producing potatoes for processing are required to apply nematicides to the soil, regardless of whether or not a nematode is detected on their sites. Therefore, a nematode in certain territories is present there, but in an amount when it can be overlooked.
Recall: once late blight destroyed crops in entire countries, causing hunger, but they learned how to deal with it by developing a routine treatment regimen. About the same thing will happen in ditylenchus. Perhaps this will not happen soon, but there is simply no other way.