Further experiments to determine the toxicity of propionic acid to fungi infesting stored grain

Abstract

Experiments were carried out on two isolates each of Fusarium culmorum (W. G. Smith) Sacc, Aspergillus Candidus Link, Paecilomyces varioti Bain, and one isolate of Cladosporium cladosporioides (Fres.) de Vries using three techniques, namely: radial growth on agar, spore germination and growth in shake culture. Dosages of 2500 ppm permitted growth of P. varioti in the radial growth technique but did not permit spore germination or growth in shake culture. The other isolates were completely inhibited at this concentration. At 1000 and 750 ppm P. varioti grew using all three techniques whereas under the same conditions only the radial growth technique permitted growth of A. candidus. At 500 ppm the radial growth technique permitted mycelial growth in F. culmorum and C. cladosporioides. Spore germination also occurred at 500 ppm in F. culmorum and one isolate of A. candidus but not in C. cladosporioides. All the isolates grew well at 250 and 100 ppm using all three techniques. The better growth performance of all isolates when using the radial growth technique is possibly due to volatilization of the acid during the exposure period resulting in a loss in concentration.