Development of a model to predict the effect of temperature and moisture on fungal spore longevity

A model was developed to quantify the effect of temperature and moisture content on the longevity of conidia of the entomopathogenic fungus Metarhizium flavoviride. This model incorporated a negative semi-logarithmic relation between longevity and temperature and a negative logarithmic relation between longevity and moisture content. Replacing the latter with a negative semi-logarithmic relation between longevity and the equilibrium relative humidity of the conidia was also effective. The latter model was applied successfully to observations on the survival of conidia of a further four entomopathogenic fungi (Metarhisium anisopliae, Beauveria bassiana, Beauveria brongniartii, and Paecilomyces farinosus) and ascospores, conidia or uredospores of four phytopathogenic fungi (Alternaria porri, Helminthosporium oryzae, Uromyces appendiculatus, and Sclerotinia sclerotiorum) across a wide range of different temperatures and relative humidities. The sensitivity of spore longevity to both temperature and equilibrium relative humidity, and the upper and lower relative humidity limits to the application of the model, varied considerably between entomopathogenic and phytopathogenic fungi, among species within each group, and among different strains within certain species. (C) 1997 Annals of Botany Company.