Selective fungitoxicity of famoxadone, tebuconazole and trifloxystrobin between Verticillium fungicola and Agaricus bisporus

The selective fungitoxicity of famoxadone, tebuconazole and trifloxystrobin between a pathogenic strain of Verticillium fungicola (Preuss) Hassebr and Agaricus bisporus (L) Sing was studied in vitro and in mushroom growing rooms. None of the above fungicides was found to be as selective as prochloraz, which inhibited the in vitro growth of V. fungicola at very low concentrations (ED50 of 0.002 μg ml−1) and was fungitoxic to A. bisporus at much higher levels (ED50 of 5.08 μg ml−1). Tebuconazole was the least selective, followed by trifloxystrobin and famoxadone, which exhibited satisfactory in vitro selectivity with ED50 values of 0.5 and 13.1 μg ml−1 for V. fungicola and A. bisporus, respectively. In trials in mushroom-growing rooms drench applications of formulated products of the above fungicides controlled the development of dry bubble disease on cultures of A. bisporus artificially inoculated with V. fungicola 6 days after casing. The fungicides were applied one day before inoculation and the disease levels observed in the cultures treated with famoxadone, tebuconazole and trifloxystrobin formulations were comparable to those obtained with the reference commercial products of prochloraz and carbendazim. Satisfactory disease control was achieved with the formulations of famoxadone, tebuconazole and trifloxystrobin used as single applications at rates equal to or higher than 0.27, 1.2 and 1.2 g active ingredient per m2 of culture, respectively. Differences in effectiveness between single and split applications were not observed. Although the number of diseased mushrooms was reduced by famoxadone, tebuconazole or trifloxystrobin, this was not reflected on yield increase or retention of basidiocarp whiteness of the commercial strains of A. bisporus used in the experiments.