The effects of fungicides on the occurrence of thermophilous leaf-surface fungi

Abstract

Thermophilous fungi were found to be a small but consistent component of the leaf surface mycoflora of living green leaves. The thirteen species of thermophilous fungi isolated occurred in higher proportions than their reported levels in the air spora indicating active growth rather than passive occurrence or preferential retention of the spores. The four fungicides, Captan, Dicloran, Thiriam and Verdasan reduced the number of thermophilous fungal isolates by 45,8%, 7.6%, 47.6% and 50.4% respectively. The frequencies of occurrence of the individual species were also suppressed to different levels; Thiram and Verdasan produced the most marked effects. Thermophilous fungi were found to be more sensitive to the fungicides than were the mesophilic species. While recolonization by the mesophilic fungi tended to reach or exceed control numbers, the thermophilous fungi remained suppressed and were often eliminated. Aspergillus fumigatus and Mucor pusillus were the major persistent species on all fungicide-treated leaves. Coprinus delicatulus, Sporotrichum thermophile and Thermoascus aurantiacus were eliminated from Verdasantreated leaves. Thermomyces lanuginosus, a major phylloplane species on control leaves, was significantly suppressed on Thiram and Verdasan-treated leaves.