Fungitoxicity of chemical groups on Myrothecium roridum in vitro and on myrothecium leaf spot on cotton plants

Abstract

The objective of this work was to evaluate the toxicity of benzimidazoles, triazoles, strobilurins, isoftalonitrils and ditiocarbamats on Myrothecium roridum conidial germination and micelial growth in vitro, and the myrothecium leaf spot severity on cotton plants. On in vitro tests, fungicides were solubilized in PDA media at the following concentrations: 0.1, 1, 10 and 100 mg L^-1. The toxicity of the products were evaluated by the ED₅₀ rate (required for inhibiting 50% of the conidial germination or mycelial growth). In greenhouse tests, the severity of myrothecium leaf spot was quantified by measuring the leaf area affected by the pathogen in cotton plants sprayed before (preventive) and after (curative) the pathogen inoculation. The fungicides thiophanate methyl, carbendazim, metconazole, thiophanate methyl + chlorothalonil, pyraclostrobin + epoxyconazole, pyraclostrobin + metiran, trifloxystrobin + propiconazole, and tebuconazole were highly efficient (ED₅₀<1 mg L^-1) or efficient (ED₅₀ between 1 and 10 mg L^-1) inhibiting conidial germination and mycelial growth of M. roridum isolates. In greenhouse tests, fungicides pyraclostrobin + epoxyconazole, tebuconazole, metconazole, and azoxystrobin + cyproconazole are the most efficient against myrothecium leaf spot disease. Preventive treatment is more efficient than curative.