Relationships of microclimatic variables to colonization of rose debris by Botrytis cinerea and the biocontrol agent Clonostachys rosea

Abstract

Biological control of Botrytis cinerea by Clonostachys rosea is an alternative to chemical control of rose Botrytis blight in greenhouses. Environmental conditions affect the colonization of senescing and dead tissues by both fungi. The contribution of microclimatic variables to debris colonization/sporulation by both fungi was estimated by path coefficient analysis. We monitored daily values of: maximum, average, and minimum temperatures (T max, T ave, and T min), and relative humidity (RHmax, RHave, and RHmin); accumulated rainfall; vapour pressure deficit average; hours with RH > 90% (RH90); and average temperature during RH90 (T ave90). Association of variables accumulated between the first and seventh day before sampling explained colonization/sporulation variation: R 2=0.81–0.86 for B. cinerea and 0.91–0.96 for C. rosea. RHmax and RH90 were the main factors that directly favoured colonization/sporulation of both fungi. Colonization/sporulation negatively correlated with RHmin, T min, and T ave for B. cinerea and T min, T ave, and T ave90 for C. rosea. The antagonist can suppress B. cinerea colonization/sporulation on rose debris under a wide range of environmental conditions.