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Dynamics of disease development in soybean cultivar Pripyat in Belarus

For agronomists

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PLANT PROTECTION P

Soybean Economics and Disease Threat

Soybean is a strategic crop that simultaneously meets food, industrial, and forage requirements. It is valued as a source of easily digestible, water-soluble protein (the main seed protein is glycinin) and essential amino acids: lysine, methionine, and tryptophan. Furthermore, soybean serves as an excellent predecessor in crop rotation. Due to its ability to fix atmospheric nitrogen, it increases the yield of subsequent grain crops by 3–5 centners per hectare.

Belarus lacks its own protein raw materials, which is why the country annually imports about a million tons of soybean meal and cake. To solve this problem, areas under soybean are being actively expanded. Production costs are recouped at a harvest of 11–13 centners per hectare, and with a yield of 20 centners per hectare or more, the crop becomes highly profitable. However, the main factor hindering the stable production of high-quality grain remains the complex of soybean diseases.

  • Yield in favorable years — 25–30 centners/ha
  • Cost recovery — 11–13 centners/ha
  • High profitability — from 20 centners/ha
  • Increase in grain crops after soybean — 3–5 centners/ha
  • Annual import of meal and cake in Belarus — 1 million tons

Dynamics of soybean acreage in Belarus: in 2014, about 5,000 hectares were allocated for the crop, in 2015 — just over 2,500 hectares, and in 2019–2020, the area remained at the level of 1,600–2,200 hectares. In recent years, growth has been noted: in 2022, the area increased to 5,800 hectares, and in 2023 reached 6,100 hectares.

Trial Conditions and Weather Impact

To track the dynamics of disease development, field studies were conducted in 2021 and 2023. The trials were set up in sowings of the early-ripening cultivar Pripyat in the Central agroclimatic zone. Agrotechnology on the plots was standard for this region. Trial plot parameters:

  • Plot area — 15 m²
  • Replication — fourfold

The degree of crop disease infestation (R) was calculated using the classic formula: R = (∑ (a × b) × 100) / (N × K). Here, ∑ (a × b) is the sum of the products of the number of diseased plants (a) and their severity score (b), N is the total number of plants accounted for, and K is the maximum score of the scale. Soybean phenological phases were recorded according to the international BBCH scale.

The development of pathogens directly depended on the hydrothermal conditions of the season. The weather during the trial years differed significantly in terms of heat and moisture distribution. All deviations from the long-term averages are grouped in the table below.

Month 2021 growing season 2023 growing season
May Cool (1.1 °C below average). At the beginning of the first ten-day period, frosts down to -2 °C were recorded. In the first and second ten-day periods, there was an excess of precipitation (154.5–308.7% of the average), in the third ten-day period — a deficit (43.2%). Average temperature +13.3 °C (within normal range). The beginning of the month was cold (3.1 °C below average), the second and third ten-day periods were warm (1.9 °C and 1.4 °C above average). Acute precipitation deficit — only 10.5% of the average.
June Hot and dry. Temperature exceeded the average by 3.9 °C, precipitation amounted to only 68.2% of the average. The first ten-day period was within the average range. In the second and third ten-day periods, the temperature exceeded the average by 3.5 °C and 2.5 °C. There was practically no precipitation until the end of the second ten-day period; rain occurred only at the end of the month.
July Hot (4.6 °C above average) with satisfactory humidity (83.8% of the average). Temperature of the first two ten-day periods was within the average range, the third — 1.1 °C higher. Precipitation: first ten-day period — 35.0% of the average, second — 32.7%, third — 137.9%.
August The first ten-day period was cold (2.8 °C below average), the second and third were warm (1.2–3.1 °C above average). Monthly precipitation — 92.6% of the average. The first ten-day period was average in temperature, precipitation was abundant (369.6% of the average). From the second ten-day period, dry heat set in, exceeding the average by 5.8 °C in the second ten-day period and by 3.3 °C in the third.

Wet Season: Early Infection and Fusarium Dominance

For an agronomist, the weather pattern at the beginning of summer is the primary marker of phytosanitary risk. With abundant precipitation and warmth, diseases of the Pripyat soybean cultivar start at early stages of the growing season, requiring timely fungicide protection. In a wet season, the total infestation of crops can reach 57.9%, and the first symptoms appear as early as the branching phase.

  • Total infestation in a wet year — 57.9 %
  • Total infestation in a dry year — 47.6 %
  • Peak of Alternaria blight during ripening — 33.6 %
  • Maximum level of Fusarium wilt — 26.2 %

In the 2021 field trials, soybean reacted with the first symptoms of infection on July 1 at stage 30 (branching). This was facilitated by the warm weather of the third ten-day period of June, with temperatures above average and abundant precipitation. Fusarium wilt, caused by a complex of pathogens including Neocosmospora solani (Mart.), Fusarium oxysporum Schltdl, and Fusarium equiseti (Corda) Sacc., developed most aggressively. Starting in the branching phase at 11.1%, by the pod filling phase (stage 75, when about 50% of pods had reached final length), the Fusarium infection grew to a moderate 26.2%.

Septoria brown spot (pathogen Septoria glycines Hemmi) also appeared during the branching stage due to a temperature of 22.7 °C and June precipitation exceeding the norm by two times. In August, heavy rains triggered a second wave of the disease, but due to their intermittency and soil moisture deficit in mid-summer, Septoria development stalled at 17.5% by stage 75. Ascochyta blight (Phoma sojicola (Abramov) Kövics, Gruyter & Aa.) and Cercospora leaf blight (Cercospora sojina Hara) developed weakly: Ascochyta blight was suppressed by high temperatures (infection did not exceed 8.6% by the fruit formation stage), and Cercospora leaf blight appeared sporadically due to a lack of moisture, affecting only 5.6% of the plants.

Critical thresholds for soybean: Fusarium infection occurs at soil temperatures from 10 to 20 °C and humidity from 20 to 100%. Cercospora leaf blight is activated in the 25–30 °C range at relative humidity of 90.0%.

Drought season: late pathogen start and Alternaria blight outbreak

Drought in the first half of the growing season can delay the development of diseases, but it does not eliminate them completely. With a moisture deficit, symptoms of infection shift to later development stages of the soybean crop. Under such conditions, pathogens that are resistant to high temperatures and capable of rapid progression during late rainfall come to the fore.

In the dry year of 2023, diseases on the Pripyat cultivar appeared only by stage 73 (about 30% of pods reached final length). The total disease index was 47.6%, but the species composition changed: fungi of the genus Alternaria were added to the main complex. Due to a hot and humid August, when the temperature exceeded the norm by 2.7 °C and precipitation reached 96.6 mm (1.4 times higher than the climatic norm of 67.9 mm), Alternaria blight showed explosive growth. By the ripening stage, the infection reached a maximum of 33.6%, which confirms its thermophilic nature (active development occurs at air temperatures of 22.0 °C and above).

The remaining diseases in the dry season were of no economic significance. The development of Cercospora leaf blight was limited to 7.2% due to uneven rainfall, even though the temperature period was favorable for it. Septoria brown spot and Ascochyta blight remained at a depressed level due to the heat: Septoria brown spot appeared in stages 73 and 82 (about 20% of pods ripened) with an intensity of 3.8%, and Ascochyta blight appeared at stage 73 with a level of no more than 1.0%. Fusarium wilt appeared extremely late, only by stage 79 (90% of pods reached final length), and its development accounted for 2.0% until the crop fully ripened.

Monitoring shows that dry weather at the beginning of summer does not guarantee clean crops at harvesting. With increased humidity at the end of the season, the thermophilic Alternaria blight can quickly infect up to a third of the entire soybean stand.

Disease and pathogen Development in the wet season (2021), % Development in the dry season (2023), % Biological optimum of the pathogen
Fusarium wilt
Neocosmospora solani (Mart.), Fusarium oxysporum Schltdl, Fusarium equiseti (Corda) Sacc		 11.1 (st. 30)
26.2 (st. 75)		 2.0 (st. 79) Temperature from 10 to 20 °C, soil moisture from 20 to 100%
Septoria brown spot
Septoria glycines Hemmi		 17.5 (st. 75) 3.8 (st. 73–82) Temperature from 15 to 30 °C (optimum 26–28 °C), air humidity 90.0%
Ascochyta blight
Phoma sojicola (Abramov) Kövics, Gruyter & Aa.		 2.5 (st. 30)
8.6 (fruit formation phase)		 1.0 (st. 73) Cold and humid weather (heat suppresses development)
Cercospora leaf blight
Cercospora sojina Hara		 5.6 (per growing season) 7.2 (per growing season) Temperature 25–30 °C, relative air humidity 90.0%
Alternaria blight
fungi of the genus Alternaria		 not recorded 33.6 (ripening) Air temperature of 22.0 °C and above with high moisture

Conclusion. The analysis of the phytopathological situation in soybean crops in 2021 and 2023 showed that crop infection depends on weather conditions. It was noted that in 2021, the Pripyat cultivar was affected by Fusarium wilt, Ascochyta blight, Septoria brown spot, and Cercospora leaf blight. The highest infection was noted for Fusarium wilt – 26.2%, which corresponds to a moderate level of development, while infection with other diseases remained at a depressed level. The total disease development in the Pripyat cultivar crops in 2021 was 57.9%. In 2023, the crop was affected by Cercospora leaf blight, Ascochyta blight, Septoria brown spot, Fusarium wilt, and Alternaria blight. The highest degree of soybean infection was noted for Alternaria blight at a moderate level of development (33.6%), with other diseases remaining at a depressed level. The total disease development in the Pripyat cultivar crops in 2023 was 47.6%.

Diseases, pests, and weeds in soybean crops in the Krasnodar Territory and control measures / V. M. Lukomets [et al.] // Oil Crops: Scientific and Technical Bulletin of the V. S. Pustovoit All-Russian Research Institute of Oil Crops. – 2007. – Iss. 1 (136). – pp. 66–75.

Main diseases in soybean crops / T. Kh. Rezvitskiy [et al.] // The scientific heritage. –

2021. – No. 59. – pp. 6–8.

4. Mycotoxins in Cereal and Soybean-Based Food and Feed [Electronic resource] // CHAPTER METRICS OVERVIEW. – Mode of access: https://www.intechopen.com/ chapters/42603 – Date of access: 29.01.2024.

Levkina, O. Optimization of soybean production parameters in the Republic of Belarus / O. Levkina, V. Vasiliev // Agrar. ekonomika. – 2018. – No. 6. – P. 46–50.

Bezmutko, S. V. Evaluation of the effectiveness of new fungicidal seed treatment agents for protecting soybean from major fungal plant pathogens / S. V. Bezmutko, I. A. Kozhevnikova // Agrar. nauka. – No. 2. – P. 165–168.

Methodological guidelines for registration trials of fungicides in agriculture / Scientific and Practical Center of the National Academy of Sciences of Belarus for Agriculture, Institute of Plant Protection; ed. by S. F. Buga. – Nesvizh: Nesvizh Enlarged Printing House named after S. Budny, 2007. – 511 p.

8. Meier, U. Growth stages of mono-and dicotyledonous plants: BBCH Monograph / U. Meier; Ed. by U. Meier. – 2 Edition. – Berlin and Braunschweig: BBA, 2001. – 158 p.

9. Mycobank Database [Electronic resource]. – Mode of access: https://www.mycobank. org/ – Date of access: 24.01.2024.

N. V. Leshkevich, E. O. Senkovsky, A. A. Zaprudsky RUE «Institute of Plant Protection», Priluki, Minsk region

DYNAMICS OF DISEASE DEVELOPMENT IN

SOYBEAN CROPS OF THE PRIPYAT VARIETY

Annotation. The article presents the results of monitoring the phytopathological state of soybean crops cultivated in the experimental field of the Republican Unitary Enterprise “Institute of Plant Protection”, where it was established that plants were affected by a complex of diseases, the main of which were fusarium (Neocosmospora solani (Mart.), Fusarium oxysporum Schltdl, Fusarium equiseti (Corda) Sacc), ascochyta blight (Phoma sojicola (Abramov) Kövics, Gruyter & Aa.), septoria blight (Septoria glycines Hemmi), cercospora blight (Cercospora sojina Hara), alternaria blight (fungi of the genus Alternaria). It was revealed that in the conditions of 2021, the dominant disease was fusarium with a development rate of 26,2 %, in 2023 – alternaria with a degree of damage of 33,6 %.

Key words: soybean, development, degree of damage, diseases, cercospora blight, septoria blight, alternaria blight, fusarium blight, ascochyta blight.

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