Phytophthora capsici Leonian is the causal agent of root, crown, and fruit rot and foliar blight and is a limiting factor in the production of vegetable crops in Michigan, the United States, and globally. Differences in symptom onset and disease severity of cucurbits to Phytophthora rot were found in laboratory and greenhouse studies. Eight fruit types were evaluated with five P. capsici isolates in a fruit experiment. All isolates incited disease with significant differences found among fruit type and pathogen isolate. Six squash crops were evaluated with the same five P. capsici isolates in seedling experiments. Crop type, pathogen isolate, or the crop type*pathogen isolate interaction term were significant for symptom appearance and area under the disease progress curve values. Phytophthora capsici and P. tropicalis Aragaki & J. Y. Uchida, formerly conspecific with P. capsici, also cause disease on tropical crops and ornamental plants. Seven Fabaceous and Solanaceous ornamental genera and seven million bells (Calibrachoa x hybrida) cultivars were evaluated for susceptibility to P. capsici or P. tropicalis in greenhouse studies. Million bells and flowering tobacco (Nicotiana x sanderae) exhibited reduced mean volumes, and P. capsici and P. tropicalis were recovered from tissue. Disease was observed on and pathogen recovery was possible from squash (Cucurbita pepo, included as a P. capsici-susceptible control), sweet pea (Lathyrus latifolius), and lupine (Lupinus polyphyllus). The potential host range of P. capsici has expanded to flowering tobacco, lupine, million bells, and sweet pea. The potential host range of P. tropicalis has expanded to flowering tobacco, squash, and sweet pea.
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