Technical Abstract: Leaf infection of ornamental species by Phytophthora ramorum has a significant impact on the spread of this disease. Fungicides have had limited effects on controlling this disease. With increasing concerns that repeated fungicide applications will exasperate the potential for fungicide resistance and mask symptoms, alternative control measures are desired. The potential of biological control has not been thoroughly examined. Fungi, isolated from soil, were screened in dual culture with P. ramorum for antagonistic activity. Three isolates, identified as Penicillium daleae, Metarhizium anisopliae, and Penicillium herquei, were selected for further testing on the aerial plant parts of rhododendrons. Different factors, including culture age, timing of application, dose response, and additives in the formulation, were studied for their effect on reducing leaf necrosis. Although responses were variable for the different antagonists, this study showed that fungi applied to the leaf surface could reduce necrosis caused by P. ramorum and provides a methodology to test and screen for more effective antagonists.