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THE DEVELOPMENT OF SLOW-RELEASED FUNGICIDE PREPARATIONS BASED ON BIODEGRADABLE POLY(3-HYDROXYBUTYRATE) TO SUPPRESS ROOT-ROT PATHOGENIC FUNGI

Svetlana V. Prudnikova

Abstract

The use of chemical crop protection products takes the lead in worldwide agricultural technologies. However, a significant part of pesticides does not achieve the goals, disperses in the environment, and accumulates in crops and food products. Targeted and controlled delivery of pesticides helps to decrease the overuse of chemicals due to the prolonged gradual release of active ingredients from matrices and maintaining of effective concentration in the application zone. The aim of this study was to evaluate the effectiveness of embedded fungicide formulations to protect crops from root-rot pathogens. Three fungicides (tebuconazole, epoxiconazole, and azoxystrobin) were embedded in biodegradable base made from a mixture of poly(3-hydroxybutyrate) and one of the fillers ? peat, clay or wood flour. The powdered components, polymer + filler + fungicide (50:30:20 wt.%), were mixed and prepared as granules. The fungicidal effect of experimental formulations on root-rot pathogens was studied in vitro and in the rhizosphere soil of test crops (spring wheat and barley) in comparison with effect of conventional methods of soil treatment with fungicides. Regardless of the filler and the type of preparation, all formulations had a pronounced inhibitory effect on the growth of Fusarium verticillioides colonies. In the field soil samples with embedded fungicides, a decrease in the number of micromycetes, in particular phytopathogenic fungi Alternaria and Fusarium, was shown. The traditional forms of fungicides affected development of saprotrophic fungi, reduced the abundance of bacteria, and shifted the ratio of dominant taxa. In contrast, no decrease in the number of bacteria in soil samples was detected when embedded fungicides was used, and besides a stimulating effect on microbial abundance was revealed. In long-term experiments with plants, the healing effect of embedded formulations on the wheat and barley roots was obtained. After tillering stage, the biological effectiveness of both embedded and free fungicides was comparable. After heading stage, the maximum biological effectiveness of embedded fungicides, reached about 90% and superior the efficacy of free fungicides, was detected. Thus, developed embedded fungicides demonstrated a long-term functioning in the soil and effective suppression of phytopathogenic fungi on the wheat and barley roots.

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