Ludmila Dulskaya
Last summer was remembered for weather disasters: many regions of central Russia and the Urals faced drought. In the Krasnodar and Stavropol Territories and the Crimea, on the contrary, there were heavy rains.
This year, the sowing season almost throughout the country began lagging behind the usual time. What problems should be feared in the new season? What can be done to save the crop? For advice, we turned to Maria Kuznetsova, Head of the Department of Potato and Vegetable Crops Diseases, Leading Researcher of the All-Russian Research Institute of Phytopathology.
Abiotic stress and nutritional deficiencies
“2021 has been a unique year. Hot dry weather prevailed in many regions of Russia. Excessively low soil moisture and lack of rainfall at high ambient temperatures have created unfavorable conditions for growing vegetable crops. Due to the lack of moisture, the plants could not fully use the fertilizers applied to the soil. This caused many functional diseases of potatoes, including: glandular spotting (rust) of tubers, darkening of the pulp, overgrowth of tubers and the formation of so-called "cheburashkas".
Potatoes, which experienced abiotic stress due to a lack of moisture and nutrients, later became very susceptible to the effects of infectious diseases of various etiologies. In addition, diseases that were present in seed tubers in a latent state began to manifest themselves more actively. In many areas of the Central part of Russia, in the Urals and some areas of Siberia, manifestations of bacterioses, anthracnose, rhizoctoniosis were massively observed, various defects of tubers were noted. Moisture deficiency also contributed to a more active damage to tubers by common scab, manifestations of verticillium and Fusarium wilt of plants.
In conditions of rainfall deficiency, herbicides did not work effectively enough. Many potato growers increased the dosages of drugs and carried out repeated treatments, which negatively affected the plants and led to chemical burns, and also contributed to the earlier manifestation of signs of alternariosis and anthracnose.
In 2021, in many regions of the Russian Federation, on different varieties of potatoes, an ultra-early manifestation of alternaria blight and later late blight was observed, which ultimately led to a decrease in the quality of tubers during harvesting. Fusarium and bacteriosis, anthracnose and pithy rot were actively manifested on the tubers during storage.
The abundance of precipitation in the Krasnodar and Stavropol Territories and partly incorrect work to protect potatoes from leaf spots led to severe damage to tubers by late blight and bacterial rot.
Getting ready for landing
What can be done to reduce the number of problems in the coming season?
Be sure to observe crop rotation (return to the field no earlier than in three to four years). Use only healthy tubers for planting. The scenario for preparing tubers for planting this season includes their mandatory warming up. Tubers need to be reviewed, discarded those that are affected by the stem nematode, with symptoms of late blight, bacteriosis, fusarium, phomosis, anthracnose. It is imperative to assess the ability of tubers to germinate, since abiotic stresses, in addition to various kinds of defects, can have a negative impact on germination.
Perform a set of measures: germination, planting of tubers, warming up the soil. Vernalized tubers planted in warm soil will sprout faster and be less susceptible to disease. Before planting or when planting, tubers must be treated with preparations from soil pathogens in order to avoid diseases such as rhizoctoniosis (“black scab”), anthracnose, silver scab.
We also note that the weather conditions of 2021, unfortunately, were favorable for the accumulation of pests. Snow fell when there was no severe frost yet, and the soil did not have time to freeze. Therefore, many pests and pathogens have survived in it.
In many regions of Russia, the presence of the Colorado potato beetle and nibbling cutworms was observed last season. Therefore, when planting, it is imperative to use insectofungicides - to reduce the harmfulness of pests and diseases.
What about imported seeds?
This season, seed potatoes from foreign countries are imported according to a simplified scheme, and the problem of the quality of seed material in Russia may worsen. Many pathogens, such as blackleg pathogens, are dormant. It is possible to import infected seeds, and we must be prepared for this.
What to do during the growing season
Be sure to carry out treatments against weeds. Last year, the protection of fields from weeds in many farms was organized incorrectly, which caused the accumulation of weed seeds and may exacerbate the problem of weediness of the plots. As you know, weeds not only change the microclimate in potato plantings, but are also reservists for diseases of bacterial and fungal etiology, so they must be fought hard, and not only in the fields, but also in the adjacent territory.
Also of great importance is the timely application of organic and mineral fertilizers: for seed potatoes, the ratio N:P:K is 1:1-1,2:1,6-2; for food - 1:0,8-1:1,5-1,8. Fertilizers affect the qualitative and quantitative composition of soil microflora, including antagonist microbes.
The best option for fertilizing is through the soil. However, under too dry or too wet conditions, foliar top dressings are a good addition - they are more effective on young leaves, when 75% of plantings are still actively growing.
It is necessary to carry out foliar top dressing, including nitrogen. You should not immediately apply the full dose of nitrogen when planting, many potato growers divide this amount into two or three doses. The first - before planting, in the amount of 60% of the total (which can be determined based on the content of mineral nitrogen in the soil in spring); the second - a week after the start of tuber formation, in the amount of 20%.
The entire volume is recommended to be applied during the first nine to ten weeks after emergence, since 90% of nitrogen is absorbed by the plant during this period.
During the growing season, nitrogen deficiency can be corrected by additional application of UAN or urea. Due to the risk of leaf burn, urea with a nitrogen concentration of more than 10-15 kg/ha should not be applied - it should be applied in several doses. This treatment can be combined with fungicide treatment against late blight and Alternaria.
It is also necessary to carry out foliar feeding of potatoes with monopotassium phosphate fertilizers - to curb the development of diseases on the leaves. And the introduction of calcium nitrate will protect the tubers from injury and infection with pathogens during harvesting, transportation and storage.
Protection against diseases
According to our information, this season, not all fungicides were delivered to Russia in full, which can create problems in organizing the protection of potatoes from late blight and early blight. It is important to remember that in conditions of strong development of diseases, only a chemical method can ensure a stable crop.
Potato growers need to review their stock of fungicides, clarify their effectiveness against late blight and early blight, and act according to weather conditions. In the table "The effectiveness of active ingredients against late blight and early blight of potatoes" indicators of effectiveness are given, which should be relied upon when choosing drugs. Let me remind you that spraying against late blight is effective when it is carried out before the disease appears in the field. And treatments against alternariosis can be started after the first symptoms of the disease appear.
Table 1. The effectiveness of active ingredients against late blight and early blight of potatoes
Active ingredient: drug | Fitoftoroz | Alternaria |
Copper preparations | + | capacitor positive (+) lead |
Dithiocarbamates | + | + |
Chlorothalonil | + | + |
Fluazinam | + | capacitor positive (+) lead |
Dimethomorph + Mancozeb | + | + |
Dimethomorph + Initium | + | — |
Cymoxanil + famoxadone | + | + |
Cymoxanil + Mancozeb | + | + |
Cymoxanil + copper | + | — |
Fenamidone + Mancozeb | + | + |
Mefenoxam + Mancozeb | + | + |
Metalaxyl + Mancozeb | + | + |
Oxadixyl+copper oxychloride | + | — |
Mandipropamide | + | — |
Mandipropamide + Difenoconazole | + | + |
Propamocarb-HCl + Fluopicolide | + | — |
Propamocarb-HCl + phenomidone | + | + |
diazofamide | + | — |
Difenoconazole | — | + |
Pyraclostrobin + boscalid | — | + |
fluapiram + pyrimethanil | — | + |
famoxadone + oxathiapiproline | + | + |
- no effect; + there is an effect
To optimize the protection of potatoes from late blight and early blight, three key periods in the development of potato plants should be distinguished: from germination to the beginning of closing of the tops in rows (phase 1), from the beginning of closing of the tops to flowering (phase 2) and from flowering to the natural death of the tops (phase 3). During the specified periods, you must perform the specified actions.
Phase 1. Spraying is justified when foci of phytophthora are detected or at a high risk of its early appearance. The mass of leaves during this period grows slowly, so any fungicide can be applied. Repeated spraying according to the traditional (routine) scheme - no later than after 7-10 days on susceptible varieties, and after 11-14 days - on resistant ones.
Phase 2. At this time, the mass of tops doubles every 4-5 days. Systemic fungicides that protect new growth of leaves and stems, according to the traditional scheme, should be applied no later than every 7-10 days on susceptible varieties, and after 11-14 days on resistant ones. Contact and translaminar fungicides should be applied to all varieties of potatoes according to the traditional scheme every 5 days.
Phase 3. The active growth of tops in this phase stops. Main goals: to protect the tops and tubers from late blight, and the tops from Alternaria. Against late blight, it is desirable to use translaminar and contact fungicides that protect tubers. Processing according to the traditional scheme - no later than every 7-10 days on susceptible varieties and after 11-14 days - on resistant ones.
At the end of the growing season, in order to prevent the transfer of diseases of various etiologies from tops to tubers and reduce the risk of damage to tubers by late blight, alternariosis, anthracnose and bacteriosis, pre-harvest destruction of tops should be carried out two to three weeks before harvesting.
Planting healthy, vernalized and insect-fungicide-treated tubers in warm soil, applying balanced doses of fertilizers, observing all agrotechnical requirements when growing potatoes, protecting plantings from weeds, pests and diseases during the growing season of plants - this is the key to a successful harvest of the 2022 season.
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