Splash dispersal of Pseudocercosporella herpotrichoides spores in wheat monocrop and wheat-clover bicrop canopies from simulated rain

Simulated rain was allowed to fall onto spore suspensions of Pseudocercosporella herpotrichoides. The resulting splash droplets were collected on horizontal traps at the bottom of a canopy and at 12 cm above treatments comprising no-crop, wheat monocrop and a wheat clover bicrop. The number of conidia collected on horizontal traps declined exponentially with distance from the inoculum source. The mean number of spores collected in the absence of any crop was twice that in a monocrop; in the monocrop it was twice that in the bicrop. Both splash droplet and spore deposition gradients were steeper in the monocrop treatment than in no-crop, and shallower in bicrop than in monocrop. Evidence is presented that suggests the clover canopy acts as a secondary source for the redistribution of previously dispersed droplets and spores.