It is presented the researches results for defeated potato tubers growing and developing the cultivar’s yield on the microelement’s feeding background (boron, copper, manganese). The positive microelement’s impact was shown on their input into the soil during the potato planting and two following nutritions on the saving the affiliated tubers.

Goal. To establish the spread of the latent form of the phomosis pathogen in the western region of the Forest-Steppe zone and to study the possibility of crop protection through the use of biofungicides. Methods. In the process of work used laboratory (cultivation of pathogens) and field (analysis, processing of tuber material). Results. The results of research conducted during 2019—2020 to detect latent infection of phomosis rot of potatoes in the western part of the forest-steppe zone of Ukraine (Zakarpattia, Chernivtsi, Ivano-Frankivsk regions) are presented. Within two years, the highest damage to tubers by latent phomosis infection was observed in varieties Yavir and Vodogray in the Ukrainian Carpathians (Ivano-Frankivsk region, Verkhovyna district, Bystrets village; Zakarpattia region, Mizhhirya district, Maidan village; Zakarpattia region, Rakhiv district, Yasinya village; Chernivtsi region, Vyzhnytskyi district, Berehomet village), which reached 25—33 and 21.0—23.0%, respectively. In the plain zone of Chernivtsi region (Hertsaiv district, Bukivka village; Novoselytsia district, UkrNDSKR IZR) a significantly lower percentage of tuber lesions with a latent form of the disease was observed. The minimum rates of tuber damage, both latent form of phomosis and with existing external signs, were observed in the variety Slovyanka and were in the plain zone 4.5—5.5% and 7.0—8.0 in the mountain. When treating tubers with biofungicides, the least pathogen tuber damage was observed in the variants using Trichodermin-Bio, PhytodoDoctor and Planriz, where the number of infected tubers was 10.0, 11.0 and 12.5%, respectively. In the control variant, the percentage of affected tubers with latent form of phomosis was 2.1—3.2 times higher than in the experimental ones. The effectiveness of biofungicides was greatest when using Trichodermin-Bio and PhytoDoctor and was 68.3 and 65.1%, respectively. Less effective drug against the latent form of phomosis, compared with other options was Hetomic, where its technical efficiency was 52.4%. Conclusions. The causative agent of phomotic rot of potatoes (Phoma exigua var. Exigua) in latent form is a widespread pathogen in the western part of the Forest-Steppe zone. To limit the spread of latent infection of phomos, biological drugs Hetomik (0.4 kg/ha) were used, Gaupbsin (5 l/t), Planriz (2 l/t), Trichodermin-Bio (2 l/t), PhytoDoctor (0.3 l/t), which helped to reduce the damage to the tubers by a latent form of the disease by 2.1—3.2 times compared to the control.

The results of studies on methods of inoculation of potato tubers when assessing resistance to Phoma exigua. For this is suitable both ways tuber infection, making inokulumu (agar blocks) in the hole and sinking bubbles in the suspension of mycelium fungus.

The researches results for ascospore stage causative agent and disease appearing in Western Forest-steppe of Ukraine were provided.

The results of studies for determining fungicides efficiency against fungal potato rot during storage are presented. The post harvesting seed processing reduces the development of the disease from 18.8 to 6.4%, and the number of affected tubers decreases from 72 to 32%. The efficiency of the used preparations is 59.6—66.0%.