Zoospore-free fluid (ZFF) stimulation of Phytophthora infection is unaffected by heat treatment. Each leaf of Catharanthus roseus cv. Little Bright Eye was inoculated with twelve 10-μl drops of inoculum of P. nicotianae at approximately one zoospore per drop. Zoospores were suspended in (A) sterile distilled water, (B) untreated ZFF from the same species at 5 × 105 zoospores ml-1 and (C) heat-treated ZFF. Disease symptoms were photographed after 3-day incubation at 23°C.