Influence of the earthworms Aporrectodea trapezoides and A. rosea on the disease severity of Rhizoctonia solani on subterranean clover and ryegrass

The influence of the earthworms Aporrectodea trapezoides and A. rosea on subterranean clover and perennial ryegrass, grown in a red-brown earth soil artificially infested with R. solani, was examined. In soil artifically infested with R. solani on wheat chaff, the presence of A. trapezoides (at a number equivalent to 300 m−2) was associated with a significant reduction in the percentage length of roots containing Rhizoctonia lesions and a significant increase in shoot weight, root weight and root length of both subterranean clover and perennial ryegrass. The presence of A. rosea, at a number equivalent to 300 m−2, was associated with a significant increase in the shoot weight and root length of subterranean clover, but A.rosea did not significantly influence the percentage root length containing Rhizoctonia lesions on either subterranean clover or perennial ryegrass. In the absence of R. solani inoculum, neither A. trapezoides or A. rosea influenced shoot weight, root weight or root length of subterranean clover. However, both earthworms significantly increased the shoot weight of perennial ryegrass in the absence of R. solani inoculum. These results demonstrate the potential of A. trapezoides and A. rosea to reduce the deleterious effect of R. solani on specific pasture plants.