Moist soil on hiking boots and bike tires has been shown to spread SOD. Vehicles driven on dirt roads that pass through SOD-infested lands may also spread contaminated soil, especially when conditions are muddy. Footwear and vehicles should be cleaned before leaving infested areas and before entering new areas (see Sidebar 3-1—Cleaning Contaminated Tools and Equipment). Dry soil poses a low risk for spreading SOD because dry soil is less apt to stick to surfaces and the amount of viable P. ramorum inoculum in dry soil is low.
Phytophthora ramorum can survive, and appears to reproduce, in streams and rivers. Watercourses that drain SOD infested watersheds are likely to contain spores of P. ramorum. More spores are typically present in watercourses during the wet season, but spores may be present in some streams year round. Untreated water from potentially infested streams should not be used for irrigation..