A range of microorganisms, with previously identified antagonistic properties towards a variety of plant pathogens, were screened for their biological control activity against the foliar necrotroph Botrytis cinerea. On detached, senescing strawberry leaves the most successful isolate, Trichoderma atroviride LU132, was able to inhibit B. cinerea lesion development and significantly reduce sporulation compared to the control treatment. T. atroviride LU132 was further evaluated under field conditions and, over a 2-year period, on three different strawberry cultivars, was able to significantly suppress B. cinerea sporulation on leaves and flower parts giving a similar level of disease control as the fungicide fenhexamid. The mechanisms of action of T. atroviride LU132 were postulated to be a combination of competition for sugars, production of non-volatile compounds and possible mycoparasitism. The strategic approach described in this paper demonstrates an efficient way of screening microorganisms for biocontrol activity and validates the notion that certain microorganisms can be antagonistic to a variety of plant pathogens.