Film-Forming Polymers and Surfactants Reduce Infection and Sporulation ofPhytophthora ramorumon Rhododendron

Abstract

Phytophthora ramorum, cause of sudden oak death and ramorum leaf blight, can persist undetected in infested nurseries. Many conventional fungicides are effective in reducing or delaying symptom expression but some may confound visual detection of infected plants. We tested film-forming polymers (FFPs) and surfactants for their ability to reduce infection and sporulation of P. ramorum on rhododendron. FFPs (Anti-Stress, Moisturin, Nature Shield, Nu-Film, and Vapor Gard) and surfactants (Tergitol, Zonix, and an unregistered AGAE product) were screened in detached-leaf assays. Anti-Stress, Nu-Film, Zonix, and a Nu-Film-Zonix mixture were additionally tested for durability, protection against exposure to infested water, and a reduction in sporulation. FFP effectiveness was retained for at least 3 weeks of exposure to overhead irrigation and rain. Relative to controls, foliar treatments protected rhododendron branches exposed to infested water. No treatments prevented symptom development when applied postinfection but leaves treated with Anti-Stress, Zonix, and the Nu-Film-Zonix mixture produced significantly fewer sporangia relative to controls. Application of FFPs and surfactants to quarantined, potentially infected plants offers a management tool for reducing infection and sporulation but not symptom expression, thereby limiting disease spread without interfering with disease detection.

Surfactants in plant disease management: A brief review and case studies

“…Biosurfactants have also shown effects on Phytophthora zoospores during experiments to evaluate surfactants and film‐forming polymers (FFP) for their potential in reducing infection and sporulation of Phytophthora ramorum on rhododendron (Peterson et al, 2016, 2019). A combination of the surfactant Zonix and the FFPs (Nu‐Film and Anti‐stress) was most effective in delaying zoospore formation, although symptom development was not reduced overall and Nu‐Film was ineffective when applied alone (Peterson et al, 2019).…”

“…Biosurfactants have also shown effects on Phytophthora zoospores during experiments to evaluate surfactants and film‐forming polymers (FFP) for their potential in reducing infection and sporulation of Phytophthora ramorum on rhododendron (Peterson et al, 2016, 2019). A combination of the surfactant Zonix and the FFPs (Nu‐Film and Anti‐stress) was most effective in delaying zoospore formation, although symptom development was not reduced overall and Nu‐Film was ineffective when applied alone (Peterson et al, 2019). In other studies, rhamnolipids produced by the bacterium Pseudomonas aeruginosa were demonstrated to inhibit motility and cause lysis of zoospores of Pythium aphanidermatum , Phytophthora capsici , and Plasmopara lactucae‐radicis (Stanghellini & Miller, 1997).…”

“…Another study with monobranched C 13 alcohol alkoxylate, including the nonioninc surfactant formulations MBA1301, MBA1303, and MBA1306, for the management of Phytophthora nicotianae on tomato showed that C 13 alcohol alkoxylate nonionic surfactants differed in their ability to lyse zoospores. MBA1306 had no effect at all, while MBA1301 and MBA1303 exhibited direct lytic effects on zoospores and reduced sporangia formation and mycelial growth(De Jonghe et al, 2007).The general conclusion was that the efficacy of surfactants against P. nicotianae depended more on the size of the polymers in the hydrophilic part of the surfactant molecule than their arrangement(De Jonghe et al, 2007).Biosurfactants have also shown effects on Phytophthora zoospores during experiments to evaluate surfactants and film-forming polymers (FFP) for their potential in reducing infection and sporulation of Phytophthora ramorum on rhododendron(Peterson et al, 2016(Peterson et al, , 2019. A combination of the surfactant Zonix and the FFPs (Nu-Film and Anti-stress) was most effective in delaying zoospore formation, although symptom development was not reduced overall and Nu-Film was ineffective when applied alone(Peterson et al, 2019).…”

Hazard Analysis for Phytophthora Species in Container Nurseries: Three Case Studies

“…Quarantined plants should not be treated with oomycete-specific fungicides so that plants that are potentially infected may express symptoms. To reduce sporulation during the monitoring period, quarantined plants can be sprayed with film-forming polymers or surfactants (Peterson et al, 2019).…”