Effect of soil pH and amendments with dried fodder rape on mycophagous soil animals and Rhizoctonia stem canker of potato

Effects of adding dried rape material to the soil and of soil pH on the ability of mycophagous springtails and nematodes to suppress stem canker on potato, caused by Rhizoctonia solani, were investigated in growth chambers. A bioassay was used with the springtail Folsomia fimetaria and the nematode Aphelenchus avenae as test organisms. Rape material, its age and the soil pH significantly affected the suppressive ability of F. fimetaria and A. avenae. Numbers of E fimetaria and A. avenae were increased when plant material was incorporated into the soil. F. fimetaria reduced stem canker under a broad range of conditions, but when rape was added to the soil at PH(-KCI) 6.2 its suppressive effect disappeared completely, probably because of the presence of alternative food sources. A. avenae only reduced stem canker at relatively high populations.