Disturbance of pasture herbage and spore dispersal of Pithomyces chartarum (Berk. & Curt.) M. B. Ellis

Abstract

Mobile spore trap counts from fixed transects on pasture herbage showed diurnal periodicity of spores of Pithomyces chartarum (Berk. & Curt.) M. B. Ellis; this was related to the diurnal progression of atmospheric humidity in settled bright weather.

In micro wind tunnel experiments, with cultures of the fungus on natural substrate, the lowest wind velocity employed (1 m/sec) detached few spores either at low or at high humidities. When the wind speed was increased to 2.7 m/sec and the air humidity reduced, increased numbers of spores were detached.

In water-drop tower studies, it was shown that large drops of water impacting on spore-bearing material detached dry spores in large numbers.

The observed rate of fall of single spores of the fungus in still air was close to the theoretical rate of fall of 0.845 cm/sec. Spores of P. chartarum already detached from litter would require only slight air turbulence to keep them airborne.

It was shown that rain falling on dry, short pasture could detach and transport spores from the litter into the air above the pasture canopy. The movements of sheep on the pasture had the same effects. It is suggested that the movement of air inspired and expired through a sheep's nostrils may detach spores from the dry litter in pastures and distribute them on to the herbage the animal may eat.

Additional information

Notes on contributors

W. E. Crawley

Now Ruakura Agricultural Research Centre, Hamilton.