The effects of fungicides on the growth rates of thermophilous fungi

Abstract

The effects of the fungicides Captan, Dicloran, Thiram, Verdasan and mercuric chloride (HgCl2) on the radial and mycelial growth rates of thermophilous fungi isolated from living green leaves were studied. On controlplates Thermoascus aurantiacus andTorula thermophila had the highest radial growth rates whileMalbranchea pulchella var.sulfurea andTalaromyces duponti had the lowest growth rates. Good sporulation was seen on all control plates. With increasing concentrations of fungicides the growth rates were correspondingly retarded and sporulation was reduced. At het higher fungicide concentrations the hyphal tips and young hyphae were thicker and warty or granulated. Of the fungi studies,Aspergillus andMucor pusillus were the most tolerant species; they were capable of growth in more concentrations of fungicides compared with the other species.Talaromyces duponti andThermomyces lanuginosus emerged as the most sensitive species. Most marked reductions in the growth rates were produced by Thiram and Verdasan than by the other fungicides. All the ten thermophilous species studied were capable of growth with more concentrations of HgCl2 than with the organo mercurial Verdasan. Six of the ten thermophilous species studied showed higher radial growth rates compared with the two fastest growing mesophilic species studied;Trlchoderma viride andZygorhynchus moelleri. While M. pusillus was capable of growth in dry weight at 0.05 ppm of all fine fungicides,Sporotrichum thermophile did not show mycelial growth with Verdasan at 0.05 ppm.Thermomyces lanuginosus showed reduced growth rates with Thiram and no mycelial growth with both HgCl2 and Verdasan.