Cross effects of zoospore-free fluid ( ZFF) from different pythiaceous species on plant infection by Phytophthora sp. ZFF was prepared from zoospore suspensions of Py. aphanidermatum (ZFFaph) and P. hydropathica (ZFFhyd) at 3 × 104 ml-1, and from P. capsici (ZFFcap), P. nicotianae (ZFFnic) and P. sojae (ZFFsoj) at 5 × 104 ml-1, respectively. Each ZFF was used as diluent to prepare inocula at a final density of 100 zoospores ml-1 (or approximately 1 per 10-μl drop) and evaluated against sterile distilled water (SDW) in three pathosystems. (A) Catharanthus roseus cv. Little Bright Eye × P. nicotianae. Ten drops of inoculum were applied to the underside of each detached leaf at different sites and infection was assessed after 3-day incubation at 23°C. Each column is a mean percentage of sites diseased (N = 54). (B) Lupinus polyphyllus × P. sojae. Two drops of inoculum were applied to each cotyledon and disease was assessed after 5-day incubation at 23°C. Each column is a mean percentage of dead seedlings (N = 30). (C) Glycine max cv. Williams × P. sojae. Two drops of inoculum were applied to hypocotyl of each seedling and disease was assessed after 4-day incubation at 26°C. Each column is a mean percentage of dead seedlings (N = 6). Bars represent standard deviation in each case.