Effects of inoculum density, wetness duration, and temperature on control of Botrytis cinerea by Gliocladium roseum in raspberry

Control of Botrytis cinerea by Gliocladium roseum was investigated in detac hed raspberry shoots maintained in high humidity. Sporulation incidence of B. cinerea in leaf disks, stem segments, stamens, and pistils respectively from shoots inoculated with 10(3), 10(4), 10(5), and 10(6) conidia of the p athogen mL(-1) increased from 13 to 100%, 7 to 100%, 38 to 100%, and 6 to 9 4%. When shoots were challenge-inoculated after 24 h with 10(4) to 10(8) co nidia of G. roseum mL(-1), in all combinations, sporulation of the pathogen was suppressed completely in leaves, and by > 97% in stems when density of the antagonist was 10(7) conidia mL(-1). Sporulation of the pathogen in st amens and pistils was suppressed more effectively when density of the antag onist was proportionately high. G. roseum developed more extensively in lea ves and stamens when postinoculation wetness lasted at least 12 to 24 h at 20 to 30 degrees C, and controlled sporulation of B. cinerea more effective ly when conditions allowed the antagonist to establish endophytically; Poly nomial regression models adequately described development of G. roseum on r aspberry as a function of wetness duration and temperature, and control of B. cinerea as a function of wetness period and temperature, and of inoculum density of G. roseum and B. cinerea. The observations have application in optimizing biological control of B. cinerea in raspberry.