Reeh, K. W. and Cutler, G. C. 2013. Laboratory efficacy and fungicide compatibility ofClonostachys roseaagainstBotrytisblight on lowbush blueberry. Can. J. Plant Sci. 93: 639-642. Lowbush blueberry (Vaccinium angustifolium) is an economically important crop. Clonostachys rosea is an endophytic fungus that can provide protection of plants from several pathogens, including Botrytis cinerea. It is unknown if C. rosea is able to colonize and protect V. angustifolium, and whether it is tolerant of fungicides commonly used for B. cinerea management in blueberry production. In a greenhouse experiment, pre-treatment of blueberry blossoms with C. rosea significantly reduced establishment of B. cinerea, but treatments after establishment of the pathogen were not effective. Clonostachys rosea demonstrated in vitro tolerance to the fungicide Switch^®, but little or no tolerance to Pristine^® and Maestro^®. Our results are encouraging for additional field research examining the use of C. rosea as part of an integrated pest management program for B. cinerea control on lowbush blueberries.