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, first of all it is necessary to clarify what kind of these roundworms the conversation is about. At present, science knows more than 30 thousand species of parasitic and free-living nematodes, while experts assume that in reality there are at least a million.
However, the professional community of potato growers is only interested in those who are able to live on potatoes and cause significant damage to the crop. This is a pale potato nematode (lat. Pale Globodera),
Golden potato nematode (lat. Globodera Roschiensis) 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 Roschiensis 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 ground part, the signs of the disease are not clearly manifested, therefore, it is almost impossible to determine the infection with Ditylenchus "by eye". At the same time, formal signs of damage on tubers (soft dark spots) can be easily confused with symptoms of fungal or bacterial rot. Even experts can speak with confidence about the presence of ditylenchus only after conducting a special analysis. But there are certain difficulties here too. Typically, damaged tubers and / or soil samples are delivered to the laboratory. Often there are cases when a nematode is found in these samples under a microscope (as already mentioned, the number of species of this microscopic worm is more than 30 thousand), but we are not always talking about a 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.
DISTRIBUTION REGIONS
We do not have exact data on the extent of the spread of the pest in Russia. The stem nematode does not belong to the number of quarantine objects, therefore, no one conducts centralized research (as is the case with the golden potato nematode). Based on the geography of inquiries to our laboratory, I can note that ditylenkhoz is found in almost all central regions of the country. The most problematic is 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. Severely 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 a pest does not entail the imposition of any punitive sanctions on the farm. But the very fact of infection (even if the percentage is not critical) should be a signal to the farmer that the work on his farm is not perfect and that at least one needs to be more careful about the choice of suppliers of seed (most often the stem nematode is imported with seeds) and be sure to check every imported consignment.
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 ditylenkhoz, planting should not be allowed, so as not to fight for the purity of their lands for 5-7 years, constantly keeping the problem under control.
METHODS TO COMBAT
The fight against any kind of parasitic nematode requires the development of a whole range of measures, taking into account the individual characteristics of each particular farm. 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 crops for infection with ditylenchus than for infection with globoderosis. The fact is that the golden potato nematode feeds only on potatoes. In order to get rid of it, do not plant this crop in the infected areas for a long enough period. 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 ditylenchus (and any other phytopathogens), production hygiene 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 several ditylenkhoz tubers are smeared, say, on a sorting table, ditylench will settle on the whole party that will follow there. And to avoid large-scale contamination is very simple - just rinse the surfaces. Even without adding fumigants, plain water will remove 99,9% of the problem. Speaking about hygiene, it is necessary to pay attention to the most complicated 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 it is also wrong to say that the pest treats all potato varieties equally. Researchers distinguish relatively resistant (less affected, with a lesion volume of up to 10%) and heavily 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 biological products, in my opinion, they are still ineffective in the fight against ditylench, 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.
PROSPECTS
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.