Evaluation of bioassays to quantify Cylindrocladium inocula in soil

Leaf discs provided better recovery of Cylindrocladium candelabrum from soil than stem or twig segments. Leaf discs of eucalypt (Eucalyptus grandis), azalea (Rhododendron sp.), and geranium (Pelargonium sp,) were the best of seven plant baits evaluated. Twig segments of azalea and eucalypt also provided a high percentage of the pathogen recovery, whereas stem segments of pine seedlings (Pinus elliottil3 proved unsatisfactory. Although slightly less effective, twig segments were easier to handle than leaf discs which were quickly decomposed in soil. Colonization of eucalypt twig segments by Cylindrocladium spp. varied with inoculum level, soil moisture content, and incubation period. The highest percentage of recovery of C. candelabrum (approx. 95%) was calculated at a field capacity moisture level of 155.9% after 75 h of incubation.