In Vitro Compatibility of Elite Indigenous Trichoderma Isolates with Commonly Used Agrochemicals for Sustainable Integrated Disease Management

Abstract

The compatibility of biological control agents with agrochemicals is critical for creating successful and long-lasting integrated disease management strategies. Five elite indigenous Trichoderma isolates (Tr79, Tr80, Tr44, Tr42, and Tr46), previously selected based on their superior antagonistic activity against three major soil-borne fungal pathogens (Fusarium oxysporum, Macrophomina phaseolina, and Sclerotium rolfsii), which pose significant threats to crop production in the Saurashtra region of Gujarat, India, were evaluated for their in vitro compatibility with 21 commercially available agrochemicals, including fungicides, insecticides, and herbicides. Agrochemicals were evaluated at four different concentrations, and compatibility was determined by calculating the percentage suppression of radial mycelial growth. The data were analyzed using two-way analysis of variance (ANOVA), followed by Tukey's Honest Significant Difference test. Agrochemical treatment, Trichoderma isolate, and their interaction significantly affected mycelial growth inhibition (two-way ANOVA, P < 0.05). Carbendazim 12% + Mancozeb 63% Wettable Powder resulted in total inhibition (100%), but Prochloraz + Tebuconazole (99.91%) and Carbendazim + Flusilazole (99.81%) both showed significant toxicity, showing poor compatibility with the tested isolates. In contrast, Imazethapyr 10% Soluble Concentrate showed no measurable inhibition and was found to be the most compatible agrochemical. Pyriproxyfen + Diafenthiuron, Fluazifop-p-butyl + Fomesafen, Carbofuran, Imazethapyr + Imazamox, and Pendimethalin were similarly very compatible, with less than 10% mycelial inhibition. The interaction between agrochemicals and isolates revealed distinct variances in chemical tolerance. These findings give significant information for determining appropriate pesticide and Trichoderma combinations that can be included in sustainable crop protection systems while limiting harmful impacts on beneficial soil microorganisms.