Fruit growing
and viticulture of South Russia
Phytosanitary condition of plants
The results of studies on the intensity of downy mildew development in the conditions of the vineyards of the Don ampelographic collection in 2019-2021 are presented. The preservation of wintering forms of mildew was facilitated by the weather conditions of the dormant periods i n 2019-2021: the absence of low freezing temperatures and sufficient humidity (61-85 %). The air temperature in the autumn-winter periods during the years of research was significantly higher than the average long-term values (the sum of negative temperatures ranged from 119.4 to 274.3 ). Under such conditions, the oospores of the pathogen, germinating at the beginning of the growing season, produce an inoculum for primary infection of plants. Phytomonitoring of the infestation of various varieties with downy mildew under epiphytotic conditions in 2021 made it possible to identify the most resistant varieties for their further use as donors of downy mildew resistance. During the growing seasons in 2019, 2020, the increased temperature, compared with the average annual values, and low humidity contributed to the depressive development of downy mildew. When the hydrothermal coefficient was from 0 to 0.5, the plants of 70-80 % of varieties had no signs of downy mildew. The intensity of disease development in other varieties did not exceed 2.5 points. In 2021, in all growing months, with the exception of July, there was a shortage of precipitation. Despite this, the increased air humidity in May-July with a hydrothermal coefficient of 0.8-1.2 contributed to the intensive development of downy mildew. As a result, 12 % of the varieties of the Don ampelographic collection showed the highest resistance to downy mildew (up to 2 points): Tavrosi; Pochatochnyy; Ol'khovskiy; Nakutvneuli; Kosorotovskiy; Grdzelmtevana. The intensity of the infestation from 2 to 3.5 points was found in 78 % of the varieties. The least resistance to downy mildew (more than 3.5 points) was manifested in 10 % of varieties: Sypunchernyy; Pukhlyakovskiy chernyy; Megrabuyr; Bessergenevskiy 1; Belobulanyy.
The cherrybark moth Enarmonia formosana (Tortricidae) causes significant damage to the trunks of fruit crops ( hawthorn, apple, cherry, pear, etc.) in the southern regions of Russia and the countries of southern and central Europe. The phenology of the cherrybark moth in the Leningrad Region has not been studied enough, which determined the purpose of this study. Pheromone monitoring of the flight dynamics of the Enarmonia formosana was carried out in the experimental orchard of St. Petersburg State Agrarian University (Pushkin district) and in the orchard Skrebovo (Luga district) in 2008-2009 and 2020-2021. Pheromone materials produced by JSC Shchelkovo Agrokhim (Shchelkovo, Moscow Region) were used, including synthetic sex attractants. Pheromone traps were placed in orchards according to the standard procedure, randomized in triplicate. As a result of trapping moths in conditions of the Leningrad region, a low number (29-31 moths per season) in 2008-2009, an outbreak of mass reproduction (524 moths) in 2020 and moderate development of the pest under the influence of seasonal abiotic factors in 2021 (297 moths) were revealed. The cherrybark moth flight dynamics in those years has been studied in detail. It is assumed that due to the continuing trends of climatic anomalies, the likelihood of a recurrence of favorable weather conditions for the cherrybark moth outbreak in orchards of the Leningrad Region is increasing. Original research and analysis of the literature have found that the cherrybark moth began to occupy a prominent place in the complex of orchard pests under the conditions of the north-west of the Russian Federation.
Worldwide studies conducted on various crops, including grapes, show the expansion of the species diversity of mycopathogens due to the appearance of new species. It is reported about the species Alternaria Nees, Fusarium Link, Aspergillus P. Micheli ex Haller, Penicillium Link, Cladosporium Link with pathogenic properties for plants on which they have not been detected before. These fungi cause leaf spotting and exist in pathocomplexes, the structures of which differ depending on the culture, the affected organ, and phenological phase. A complex of fungi was found on the grapes, which causes necrosis of the leaves and serious damage to the photosynthetic apparatus of the plant. A strong development of the disease leads to the death of the leaf plate. In our study, 13 species of fungi isolated from necrotic leaves were found. The dominant fungi are Alternaria Nees, the common Aspergillus niger Tiegh., Mucor Fresen., Fusarium Link. Minor Components are Penicillium Link, Aspergillus flavus Link, Trichoderma Pers., Cladosporium Link. The composition of the mycopathocomplex is dynamic, varies depending on the phenological phase and abiotic conditions. Aspergillus niger Tiegh and Fusarium Link is found on young leaves with necrotic damages together with Alternaria fungi. In hotter and drier July, the number of Aspergillus fungi increases, but the percentage of occurrence of Alternaria and Fusarium decreases. In August-September, on old and weakened leaves, Mucor Fresen was much more common in the mycopathocomplex, which may indicate its necrotrophy in relation to grapes.
To develop protective measures, it is necessary to identify the most dangerous and new harmful objects, as well as to select drugs with high efficiency. However, it is not always possible to assess the effectiveness of inhibition of a particular fungus species by chemical preparations; in addition, many phytopathogens can acquire a certain level of resistance to fungicides. For this reason, it becomes necessary to study the effectiveness of drugs against individual species using laboratory methods using pure cultures of fungi. The in vitro method makes it possible to evaluate the effectiveness of chemical preparations against pathogens in a fairly short time. However, there is the problem of the lack of a standardized method for assessing antifungal activity against economically important pathogens of agricultural crops. The studies were performed by two methods depending on the method of introducing the drug into the medium: by agar stab technique with a uniform introduction of the drug onto the surface of the nutrient medium and by inoculation the conidial suspension of the pathogen with a microbiological spatula when the drug is introduced on paper disks. The antifungal activity of chemicals against the fungus Alternaria alternata, the causative agent of apple fruit rot, varied in a wide range from no effect to strong, but in most variants of the experiment it was medium and the data obtained by the two methods of study were comparable. Comparison of these two methods showed a different degree of reproducibility of the results. So the most stable and repeatable results were given by the method with a uniform application of the working concentration of the drug to the surface of the nutrient medium and sowing by injection. In our study, the disk-diffusion method turned out to be more laborious, and the effects obtained by this method were not always characterized by an unambiguous interpretation and differed in repetitions, in comparison with the method in which the fungicide was applied directly to the agar plate, and the sowing was carried out by agar stab technique. Further optimization and standardization of this method is needed, including the amount of fungal inoculum applied and the thickness and evenness of the agar plate.
The analysis of the epiphytic microflora of the leaves of wild grapes growing in the forest near the river and the mountain slope of the Crimean district was carried out. The research was carried out in 2020-2021. The number and structure of complexes of micromycetes associated with grape leaves were determined by swab test method of diluted suspension on a dense nutrient medium (PSA). The structure of the complex of micromycetes associated with leaves in grape plants growing in the floodplain of the river in the spring period was characterized by an abundance of yeast (61,3%), and in plants growing in the forest, mycelial, yeast and yeast-like fungi were approximately in equal proportions. By the beginning of autumn, mycelial fungi dominated in the structure of micromycetes of both ecotopes. The total number of microscopic fungi on the leaf surface of wild grapes changed under the influence of environmental conditions. The leaf apparatus of grape plants from the forest had a smaller number of micromycetes (on average for 2 years ranged from 1315.2...5094.7 thous. CFU /1gr dry matter), compared with plants growing in the floodplain of the river (on average for 2 years ranged from 5116.1 to 9279.7 thous. CFU /1gr dry matter). Thus, the total number of microflorae of grape leaves is affected by the humidity regime of the air and soil. Species of the genus Cladosporium sp. 44.4 % (May), Phomopsis sp. 65.8-78.2 % (July-September) were distinguished as dominant on the leaves of wild grapes of the forest area during the growing season. In the sample growing in the floodplain of the river, the dominant ones were: Phomopsis sp. (54.8 % in May; 82.4 % in September) and Cladosporium sp. (53.6 % in June; 35.3 % in July).