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

Abstract

Control of Botrytis cinerea by Gliocladium roseum was investigated in detached raspberry shoots maintained in high humidity. Sporulation incidence of B. cinerea in leaf disks, stem segments, stamens, and pistils respectively from shoots inoculated with 10³, 10⁴. 10⁵, and 10⁶ conidia of the pathogen mL^-1 increased from 13 to 100%, 7 to 100%, 38 to 100%, and 6 to 94%. When shoots were challenge-inoculated after 24 h with 10⁴ to 10⁸ conidia 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 10⁷ conidia mL^-1. Sporulation of the pathogen in stamens and pistils was suppressed more effectively when density of the antagonist was proportionately high. G. roseum developed more extensively in leaves and stamens when postinoculation wetness lasted at least 12 to 24 h at 20 to 30°C, and controlled sporulation of B. cinerea more effectively when conditions allowed the antagonist to establish endophytically. Polynomial regression models adequately described development of G. roseum on raspberry 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.

Keywords:

• Rubus idaeus
• gray mold
• biological control