The effects of methyl bromide alternatives on soil and seedling pathogen populations, weeds, and seedling morphology in Oregon and Washington forest nurseries

Abstract

Five fumigation treatments (a conventional methyl bromide -chloropicrin application and four reduced-rate alternative fumigant treatments) and a nonfumigated treatment were evaluated at two forest nurseries in Oregon and one forest nursery in Washington for their effects on soil pathogen populations, weeds, and seedling morphology during a 2-year study.

PythiumSpecies and Isolate Diversity Influence Inhibition by the Biological Control AgentStreptomyces lydicus

“…In that study, 100 isolates were originally selected at random from each of the three nurseries (nursery A in southwestern Washington and nurseries B and C in northwestern Oregon) and from each of three isolation methods used at each nursery (dilution plating and baiting with rhododendron leaf disks or Douglas-fir needle segments) to yield 900 total isolates (300 isolates from each nursery). These three species were also chosen based on their association with damping-off disease of conifers in previous studies (20,41,44,45), and their presence in comparatively large numbers at more than one nursery during the 2008 survey (43). Isolates were subsequently selected for this study as representatives of 16 of the 19 species found at the three nurseries.…”

“…cause damping-off and root rot in forest seedling nurseries worldwide and are considered one of the most important soilborne pathogens affecting tree seedling production (41,(44)(45)(46). cause damping-off and root rot in forest seedling nurseries worldwide and are considered one of the most important soilborne pathogens affecting tree seedling production (41,(44)(45)(46).…”

Forest nurseries face critical choices with the loss of methyl bromide fumigation

“…Iodomethane with chloropicrin has been successful in soil disease and weed control, in both spring (80:20 at 275 pounds per acre) and fall applications (50:50 at 175 to 350 pounds per acre) (unpublished industry data and Weiland et al 2011).…”

“…Much of the groundwork was accomplished by R. L. James and colleagues, who identified pathogenic species of Fusarium and Pythium (e.g., James 2002). More recently, a number of new Fusarium and Pythium species have been described from forest nursery soils (Weiland 2011;Weiland et al 2011), and research has identified eight Pythium species that are virulent pathogens of Douglas-fir seedlings (Weiland et al 2013).…”

“…However, if they can be coordinated into a cohesive integrated pest management program, successful pest control might be achieved. Weiland et al (2011), for example, found promising results in nurseries that used bare fallow in combination with reduced-rate fumigants under VIF.…”