ABSTRACT
The purpose of the present study was to evaluate biological activity of slowrelease fungicide formulations for suppressing potato pathogens. Fungicides embedded in degradable poly-3-hydroxybutyrate/wood flour matrix for preemergence soil application were studied. The slow-release fungicide formulations (azoxystrobin (AZ), azoxystrobin + mefenoxam, and difenoconazole (DIF)) were compared with their commercial analogs (Quadris, Uniform, and Score) in the in vitro experiments, using disk diffusion test, and in the in vivo experiments with potato cv. Krasnoyarskiy ranniy. In cultures of plant pathogens, the embedded fungicides showed an inhibitory effect comparable to their commercial analogs, most effectively controlling the growth of 140colonies of Phytophthora infestans, Alternaria longipes, Rhizoctonia solani, and Fusarium solani (2.0–2.3 times relative to the negative control). In the in vivo experiments, with the same phytosanitary condition of seed tubers and the initial soil, potatoes were damaged by pathogens in different ways. In laboratory experiment, only Rhizoctonia species developed; in the groups with embedded fungicides, germination occurred earlier, potatoes grew better, and the area of damage of the plants was reduced to 10% or less; the weight of microtubers from one clone was 25–35% greater compared to the control; the yield increase ranged between 60% and 71.3%. In the field experiment, the embedded fungicides inhibited the development of Phytophthora and Alternaria in the rhizosphere during the entire growing season and reduced the area of pathogen damage to plants to 10–15%, which was less by a factor of two than in the groups of plants treated with commercial fungicides. The higher biological activity of the embedded fungicides ensured the maximum number of tubers undamaged by pathogens and the total yield of 22–23 t/ha, which exceeded the yields in the groups with commercial fungicides (18.4–20.8 t/ha). The slow-release fungicide formulations prepared by embedding fungicides in P(3HB)/wood flour degradable matrix are effective in protecting potatoes from pathogens and in increasing potato yields and have an advantage over their commercial analogs.
