Effectiveness of Vehicle Washing and Roadside Sanitation in Decreasing Spread Potential of Port-Orford-Cedar Root Disease

Abstract

Two techniques widely recommended for managing Port-Orford-cedar root disease (caused by the introduced pathogen Phytophthora lateralis) are vehicle washing and roadside sanitation. However, their effectiveness has never been tested using a sample-based approach. Vehicle washing effectiveness was evaluated using Port-Orford-cedar seedling baits and a double-washing method. Washing with water can significantly reduce the amount of inoculum adhering to vehicles and boots. Effectiveness of roadside sanitation, the creation of zones along roads with few or no living Port-Orford-cedar hosts, was monitored using seedling baits for up to 12 years along ten infested roadsides that received operational treatments and for 8 years along four that did not. Sanitation treatments greatly reduced the amount of inoculum over time. Inoculum decline became most substantial in years 4 to 12 after treatment, suggesting that this treatment would be most useful in long-term strategies on roads used for many activities rather than in the short-term. Implementation monitoring of 17 roads that were sanitized by contract crews demonstrated that contractors were very thorough in removing all Port-Orford-cedars that met contract specifications. Vehicle washing and sanitation treatments reduce the likelihood of P. lateralis spread and are appropriate for use with other techniques in disease management strategies.