Evaluation of Toxicity of Agrochemicals on Trichoderma isolates In vitro

Abstract

Thirty nine agrochemicals comprising eighteen fungicides, eleven insecticides, six fertilizers and four herbicides were evaluated at different concentrations against two isolates of Trichoderma spp., and EC₅₀ and EC₉₀ values were calculated based on inhibition in radial growth. Isolate T. virens TV9, obtained from citrus orchard-relatively less exposed to agrochemicals was found more sensitive compared to isolate T. harzianum Th4, obtained from cotton ecosystem relatively more exposed to agrochemicals. Among fungicides, benzimidazoles showed higher toxicity followed by chlorothalonil and triazoles when mean EC₅₀ values were compared. Wettable sulphur, Bordeaux mixture, azoxystrobin and mancozeb were found to be less toxic to Trichoderma spp. Among insecticides, organophosphorous group was found more toxic while carbofuran followed by spinosad were least toxic. Among fertilizers Zinc sulphate and diammonium phosphate were found highly toxic whereas potassium nitrate, muriate of potash and ammonium sulphate showed less toxicity. All the four test herbicides, i.e., pendimethalin, alachlor, glyphosate and 2, 4-D were found to be toxic to Trichoderma spp.