This plant pathogen lives in the soil and survives Michigan winters. It does not move via air currents but spreads via splash of contaminated soil, surface water such as culverts, rivers, creeks and streams contaminated by run-off from infested fields, and the dumping of diseased culls onto production fields. Phytophthora is especially unique because it can develop a swimming spore when the soil becomes saturated. The swimming spores move across a field in a pattern consistent with draining water and kills plants in its path (see fact sheet on Phytophthora and irrigation water). Squash, zucchini, pepper and pumpkin are especially susceptible. Plants that wilt and don’t recover can be a tell-tale symptom of this disease.
Phytophthora fruit rot of pumpkin. Photo by Mary Hausbeck, MSU.
