Growth-Promoting Effect of Microorganisms and Chemical Fungicides Used in Combination on Tomatoes

The research was conducted to evaluate the growth-promoting activity of microorganism strains and their combinations with active ingredients of synthetic preparations on tomato plants for the development of integrated biopesticide formulations that ensure effective plant protection while reducing chemical load on agroecosystems. The work was carried out in 2025 under laboratory and vegetative conditions, with biometric indicators recorded on days 30, 60 and 90. Microbial strains Pseudomonas aureofaciens BS 1393, Pseudomonas fluorescens WCS 365, Pseudomonas putida PCL 1760 and Trichoderma asperellum T302, as well as the chemical fungicides mandipropamid and difenoconazole, and their combinations with microorganisms, were used on Khurma tomato cultivar. Pesticide concentrations were used at reduced doses (two times lower than manufacturer’s recommendations). A statistically significant positive effect of all biological agents on tomato growth and productivity was established. The pure T. asperellum T302 strain demonstrated the greatest effect in the experiment, increasing stem height by 145.8% and average fruit mass by 22.5% relative to the control. A synergistic effect was revealed with combined application of the studied agents: the combination of mandipropamid with P. putida PCL 1760 increased root length by 65.7% (5.8 cm versus 3.5 cm) compared to the pure preparation and provided maximum fruit mass (228.2 g, +24.4% compared to the control), while the combination of difenoconazole with P. aureofaciens BS 1393 ensured stable fruiting (3 fruits per cluster). The ability of bioagents to reduce the phytotoxicity of chemicals was confirmed, as well as the possibility of their use in this combination at half doses without loss of effectiveness. The experimental results demonstrate the potential for developing complex biopesticide compositions for greening plant protection.