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Video: How To Deal With Potato Glodoberosis
Disease characteristics, control measures and resistant potato varieties
The defeat of tubers by a nematode has now become such a serious problem that the leading breeders of our region are now setting themselves up to release, first of all, nematode-resistant varieties.
Among the most serious problems of potato growing in Russia is the spread of diseases (globoderosis) caused by nematodes (genus Globodera Globodera). There are two types of cyst-forming potato nematodes - golden and pale, which are quarantine objects both in our country and abroad.
According to leading nematodologists, the second species has not yet been found in our country, but the range of the first is constantly expanding, and the yield losses are growing because of this. The harmfulness of the golden nematode depends on the number of the parasite, the level of soil fertility and the resistance of the cultivated varieties. It was revealed that with an average degree of field contamination, yield losses can be 20-30%, with a strong one - 70-80%.
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In our country, the danger of large losses of potato yield from nematodes is especially great. The fact is that the owners of backyard plots, as a rule, use poor quality planting material, grow potatoes for many years in the same place, and often use susceptible varieties, which leads to the accumulation and spread of infection. This is also facilitated by the difficultly controlled transportation of small batches of tubers within the country, as well as the lack of a method for disinfecting tubers and soil. On household plots in the outbreaks of severe infection, the yield shortfall can exceed 70%.
Determine the presence of a nematode on the site at the threshold of the number when it begins to harm, only a "narrow" specialist - a nematodologist from the plant protection service or quarantine inspection - is able to. Official services with a high degree of probability state that, in addition to the already registered outbreaks, there are outbreaks where the concentration of nematode larvae has not yet reached a level that can be detected by existing methods of soil diagnostics or infestation of susceptible potato varieties. Therefore, many advocacy scientists working with potatoes tend to assume that at least 80% of the individual sector is already infected with this object.
The expansion of the area of the golden nematode is associated with the peculiarities of its preservation and transfer: with the smallest lumps of soil, potato tubers, agricultural implements, with the presence of dormant stages of cysts, well protected from the influence of unfavorable environmental factors, which makes it difficult to fight. This is due to the fact that in the first years of infection of the site, it is impossible to detect the pathogen. The cycle of development of the parasite takes place in the roots of the host plant. In spring - at the beginning of summer, second instar larvae emerge from the preserved cysts into the moist and warm soil.
They have a good orientation towards isolating the roots of the affected plants, which stimulate the massive and rapid release of larvae from the cysts and infection of the potato roots. In the absence of a host plant, only a small number of larvae emerge from the cysts and die. The individuals remaining in the cysts can remain alive for up to 10 years or more. Under unfavorable conditions (insufficient soil moisture, low temperature and poor aeration), the release of larvae from cysts and their penetration into the roots decreases.
In the roots, the larvae lose mobility, feed on the contents of the cells, and during the growing season to an adult state, they undergo three stages of development. Females produce oval-shaped eggs in the ovaries, which remain inside their bodies. The number of eggs ranges from several tens to several hundred, depending on the supply of females with food. The nematode has several pathotypes (sort of groups), differing in their aggressiveness and ability to reproduce on various species of nightshade (and, possibly, to switch from one to another).
After laying eggs (in the ovaries inside the body), the female dies off, her cuticle thickens, hardens and becomes brown. Such dead females with eggs inside are called cysts. At the end of the growing season, the cysts with the larvae developed in them fall off the root system and hibernate. The biological cycle of a potato nematode lasts about two months (gives the first generation).
The focus of globoderosis is found, as a rule, 5-7 years after the introduction of cysts on the site during monoculture: the presence of diseased plants is striking in the beds. They lag behind in growth and development, have a depressed appearance, the lower leaves turn yellow and wither, the roots become fibrous, the tubers are small or completely absent. There may be several outbreaks in the field. The degree of yield decline depends on the amount of nematode in the soil, on the variety of potatoes, on the type of soil, the level of its fertility and weather conditions. Sometimes in the formed "bald patches" the crop dies completely.
It is possible to detect the parasite on the site by examining the plants that have lagged behind in development, from mass flowering to harvesting. The bush is carefully dug up and, without shaking off the ground, the root system is examined. On the roots of the infected bush, with the naked eye, you can see small, poppy seed-sized, rounded yellow females, as well as brown-golden cysts.
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Nematode control measures
It is always easier to prevent soil contamination than to deal with potato nematode outbreaks later. To do this, the following rules must be observed: do not plant unknown seed material (with it you can bring in a nematode) and do not bring manure from the farm where this nematode is available.
If a nematode has entered the area or causes significant damage to the crop, it is necessary to stop growing potatoes and occupy the area with other non-affected crops (for example, legumes (especially lupines), perennial grasses or beets. In a monopoly system, the influence of the nematode can be reduced by sowing green manure after potatoes (winter rye) in order to bury it later in the late spring.
Almost complete death of nematodes within three years is provided by the alternation of crops with the introduction of urea at a rate of 5 kg / weaving (in three doses) according to the scheme: "potatoes (nematode-resistant variety) - legumes - beets - potatoes (nematode-resistant variety)". Anti-nematode crop rotations with resistant varieties sharply reduce the number of phytohelminths: already in the first years of the struggle, a small number of cysts remains in the soil. There is reason to pin some hopes on growth regulators: pre-planting treatment of tubers with drugs (silk or epin) increases the mass of plant roots by 20-60%.
But since it is difficult for the owners of many household plots to organize a long-term crop rotation of crops (with the appearance of potatoes on the site in 5-6 years), then for them the most optimal way to combat the nematode is the use of resistant and tolerant (hardy) varieties. It is necessary to come to terms with the fact that some available nematode-resistant varieties are inferior to susceptible varieties in taste and culinary qualities, yield and resistance to other pathogens.
But here, as they say: "Of two evils, choose the lesser" and "The invisible enemy is more terrible than the visible" (for example, phytophthora or Colorado potato beetle). Non-malignant varieties can give a fairly high yield on infested areas and at the same time clear the soil. Resistant varieties act as “hostile” plants for the nematode: the substances they release stimulate the release of larvae from cysts, their penetration into the roots of resistant varieties and death before reaching sexual maturity.
The nemato-purifying effect of using resistant varieties reduces high infestation by 80-90%, and with a weak one - by 100%, since females do not develop on the roots of such plants. But you just need to remember that the same nematode-resistant variety cannot be grown for more than 4-5 years in a row (subject to crop rotation and the introduction of organic fertilizers), so that an aggressive pathotype does not appear.
But the nematode is able to recover very quickly when susceptible varieties return, so it is very important not to mix the seed tubers of resistant and susceptible varieties.
In order to reduce losses from nematodes to an economically imperceptible level, in recent decades, breeders have taken the direction of breeding varieties resistant to it. If in 1988 there were only four such varieties in our country, now there are more than 60 of them (among them there are many foreign ones), i.e. every third. In the Leningrad Region, their saturation is 25%, but in Russia so far - less than 10%. Now the potato grower can choose when buying varieties that are different in early maturity, yield, resistance to other harmful objects; it is necessary to require that there is a mandatory complete characterization of the variety being sold.
Now the State Register of Russia is published annually for potato varieties, I will cite from it only a part of the list of varieties resistant to nematodes.
These are the majority of German varieties (especially early maturing). But they are highly or moderately susceptible to late blight and Alternaria - Arnica, Granola, Dennitsa, Zekura (mid-early), Karatop, Panda, Planta, Rosara, Sanita, Skala (early-maturing), Spekula. The Dutch varieties Agria, Accent, Amadeus, Asterix, Diamant, Cardinal, Symphony (mid-ripening), Anosta, Latona, Concord, Prior, Impala, Fresco, Ukama (early-ripening), Bimonda, Lizatta, Nikita, Pamir, Sante behave about the same., Hertha (mid-early).
The nematode-resistant domestic varieties include varieties of the VNIIKH selection - Aspia, Zavorskiy (mid-season); Hand, Lukyanovsky, Russian woman, Bezhitsky (mid-early); Zhukovsky early; breeding of the North-West of Russia - Rozhdestvensky (mid-early), Pushkinets (early), Eliseevsky, Naiad (formerly Nematode-resistant-26) (mid-season).
Late-ripening varieties include Lady Rosetta (Gollania) and Naroch, Skarb, Prigozhiy-2, Belorussky-3 (all Belarus), Malinovka (medium late) (VNIIKH).
Super early varieties (for example, Zhukovsky early) can also have a positive effect on the situation with nematodes, the cultivation of which for early production, even without preliminary germination of seed tubers, will significantly clear the soil in the individual sector.
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