Optimization of the method for determining nitrogen balance in apple leaves when assessing the effectiveness of fungicides for scab

Under conditions of apple scab (Venturia inaequalis) epiphytotics, optimizing instrumental approaches adopted to assess the physiological state of plants becomes an urgent task. The study aims to develop and test a method for non-destructive rapid assessment of nitrogen balance in apple tree leaves (Malus domestica Borkh.) using the nitrogen balanceindex (NBI) to analyze the effectiveness of various fungicide protection schemes. The experiment began in 2024 as part of a three-year study into the biological effectiveness of fungicides for apple scab in the apple orchard of Solnechnogorsky District of Moscow Oblast on the Mantet, Melba and Lobo cultivars. The experiment included four variants: two proposed schemes under study with sequential triple administration of a contact fungicide, followed by double application of a systemic preparation. Scheme No. 1 involved using Merpan, WP (500 g/kg captan) – 3 kg/ha + Znatok, WDG (500 g/kg trifloxystrobin) – 0.14 kg/ha. Scheme No. 2 included Shrapnel, WSG (700 g/kg dithianon) 0.7 kg/ha + CipAgro, WDG (750 g/kg cyprodinil) – 0.2 l/ha, commercial fungicide protection system (with a predominance of difenoconazole) and control (water treatment). NBI index measurements were performed on 3 July and 3 September using a Dualex device on leaves of three age groups. Comparison of the methods showed that the 30 × 1 approach (30 points on one leaf) provides less variability (SD ranges from 1.99 to 3.62) compared to the 6 × 4 approach (6 points on each of 4 leaves). Leaf age had the greatest effect on NBI (24.7% of variance, p < 0.05). The study established reliable inverse correlations between the NBI level and the spread (ρ = -0.615, p <0.05) and development (ρ = -0.601, p <0.05) of scab. It was observed that the protection scheme with captan and trifloxystrobin enabled the maximum increase in NBI during the growing season (up to +5.25 units). The obtained results confirm the effectiveness of using NBI as an objective criterion for assessing fungicidal protection under conditions of high infection pressure.

1. Polozhikhina M. A. Possibilities and problems of import substitution (on the example of apple production), Vestnik Moskovskogo Universiteta. Seriya 6: Economics. 2022;4:80-96. (in Russ.).

2. Naumova L. L., Lukin A. A., Velisevich V. A. Consumer properties and nutritional value of winter apples, Polzunovsky Vestnik. 2023;3:101-106. DOI: 10.25712/ASTU.2072-8921.2023.03.013. (in Russ.).

3. Beloshapkina O. O., Vahsheh I. N. N., Ryabchenko, A. S. Influence of chemical and biological preparations on Venturia pyrina – pathogen of pear scab, Mikologiya i Fitopatologiya. 2015;49(1):48-53. (in Russ.).

4. Nasonov A. I., Yakuba G. V., Lobodina E. V. Long-term preservation of resistance to carbendazim in Venturia inaequalis in Krasnodar Krai (Russia), Mikologiya i Fitopatologiya. 2022;56(5):374-378. DOI: 10.31857/S0026364822050087. (in Russ.).

5. Kashirskaya N. Y., Kochkina A. M. Modern protection systems of apple plantations from scab, Achievements of science and technology in agro-industrial complex. 2019;33(2):50-51. DOI: 10.24411/0235-2451-2019-10212. (in Russ.).

6. Nasonov A. I., Yakuba G. V., Bardak M. V., et al. Evaluation of ‘fitness cost’ in Venturia inaequalis resistant to difenoconazole, Mikologiya i Fitopatologiya. 2025;59(2):154-168. DOI: 10.31857/S0026364825020042. (in Russ.).

7. Pikunova A. V., Sedov E. N. The Racial Composition of Venturia inaequalis in Environments of the Oryol Region, Mycology and Phytopathology. 2019;53(5):293-300. DOI: 10.1134/S0026364819050040.

8. Nasonov A. I., Yakuba G. V. Apple scab: resistance to chemical fungicides, Mikologiya i Fitopatologiya. 2024;58(2):91-107. DOI: 10.31857/S0026364824020018. (in Russ.).

9. Terentyev A., Dolzhenko V., Fedotov A., et al. Sovremennoe sostoyanie giperspektral’nogo distancionnogo zondirovaniya dlya rannego vyyavleniya boleznej rastenij: obzor, GIS Proxima, 2023, URL: https://gisproxima.ru/sovremennoe_sostoyanie_h (accessed: 18.05.2025) (in Russ.).

10. Yu K., Leufen G., Hunsche M., Noga G., Chen X., Bareth G. Investigation of Leaf Diseases and Estimation of Chlorophyll Concentration in Seven Barley Varieties Using Fluorescence and Hyperspectral Indices, Remote Sensing. 2014;6(1):64-86. DOI: 10.3390/rs6010064.

11. Kviklys D, Viškelis J, Liaudanskas M, Janulis V, Laužikė K, Samuolienė G, Uselis N, Lanauskas J. Apple Fruit Growth and Quality Depend on the Position in Tree Canopy, Plants (Basel). 2022;11(2):196. DOI: 10.3390/plants11020196.

12. Holm G. Chlorophyll mutations in barley, Acta. Agr. Scand. 1954;4:457-471.

13. Dymova O. V., Golovko T. K. Photosynthetic pigments in plants of the natural flora of the taiga zone of northeastern European Russia, Fiziologiya rastenij. 2019;66(3):198-206. DOI: 10.1134/S0015330319030035. (in Russ.).

14. Sautkina M. Y. Comparative assessment of the content of photosynthetic pigments in English oak leaves in protective forest belts, Journal of Agriculture and Environment. 2022;21(1):18. DOI: 10.23649/jae.2022.1.21.18. (in Russ.)

15. Giniyatullin R. K., Ivanov R. S., Tagirova O. V., et al. Content of photosynthetic pigments in healthy and weakened trees of Populus balsamifera in industrial pollution conditions, (Respublika Bashkortostan, Sterlitamakskij promyshlennyj centr), Samara journal of science. 2022;11(1):43-48. DOI: 10.55355/snv2022111104. (in Russ.).

16. Kalmykova E. V., Melnik K. A., Kuzmin P. A. Species differences in the content of photosynthetic pigments in plants of arid territories of southern Russia, Agrarny Vestnik Urala. 2023;3:32-42. DOI: 10.32417/1997-4868-2023-232-03-32-42. (in Russ.).

17. Croft H., Chen J. M. Leaf pigment content, Comprehensive Remote Sensing, S. Liang (ed.), Oxford: Elsevier. 2018;3:117-142. DOI: 10.1016/B978-0-12-409548-9.10547-0.

18. Kovac D., Veselovska P., Klem K., et al. Potential of photochemical reflectance index for indicating photochemistry and light use efficiency in leaves of European beech and Norway Spruce trees, Remote Sensing. 2018;10:1202. URL: https://www.mdpi.com/2072-4292/10/8/1202 (дата обращения: 19.05.2025). DOI: 10.3390/rs10081202.

19. Tyulkova E. G. The influence of technogenic conditions on the content of photosynthetic pigments in trees of different age groups, Vesnik Brestskogo Universiteta. Seriya 5: Khimiya. Biologiya. Nauki o Zemle. 2019;1:52-60. (in Russ.).

20. Chernyavskaya I. V., Ednich E. M., Tolstikova T. N. Content of photosynthetic pigments in Acer spp. in urban conditions, Siberian Journal of Life Sciences and Agriculture. 2023;15(5):153-171. DOI: 10.12731/2658-6649-2023-15-5-931. (in Russ.).

21. Nasonov A. I., Bardak M. V. Morphotypic composition and sensitivity to difenoconazole of Venturia inaequalis populations, Siberian Journal of Life Sciences and Agriculture. 2023;15(3):219-238. DOI: 10.12731/2658-6649-2023-15-3-219-238. (in Russ.).