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

Abstract

Forest nurseries in the western UnitedStates have relied for decades on methyl bromide to control soilborne pests. Numerous studies have investigated alternative fumigants, alternative application methods and nonfumigant approaches for their ability to reduce soilborne pest populations and produce quality, disease-free seedlings. We review the recent studies and identify where research is needed to assist the industry's transition away from methyl bromide. For the immediate, foreseeable future, an integrated approach combining nonfumigant and fumigant methods will provide the best strategy. Nevertheless, the industry may need to transition completely to container production if fumigant regulations become more restrictive.

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

“…The diversity of pathogen communities and populations, in contrast, is not directly controlled and may be quite variable (6,32,37). Another strategy that may hold promise is the combination of BCAs with fungicide treatments or other soilborne disease control measures such as bare fallow, irrigation management, or organic amendments (46). were identified from field soil samples (43).…”

“…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).…”

“…Although there are many BCA studies that assess several pathogen species or isolates, the number of species or isolates evaluated is usually extremely limited and, as a consequence, there is limited statistical inference about the contribution of pathogen species or isolate diversity to BCA inhibition (5,6,11,28,(35)(36)(37)48,50). Knowledge about the degree to which BCA inhibition is influenced by pathogen species and isolate diversity is particularly relevant to the forest nursery industry, where multiple Pythium spp., each consisting of numerous isolates, are found within a single nursery field (16,43,46). In many cases, the pathogen isolates were collected from different geographic locations, plant hosts, or culture collections (9,11,22,26,29,32,35,37,38,42,48,50).…”

Efficacy of reduced rate fumigant alternatives and methyl bromide against soilborne pathogens and weeds in western forest nurseries

“…Forest nurseries in the western states of California, Idaho, Montana, Oregon, and Washington produce approximately 200 million tree seedlings each year, mainly for reforestation purposes (Weiland et al, 2013b). Most seedlings sold in the region are Douglas-fir (Pseudotsuga menziesii (Mirb.)…”

“…Soilborne disease and weed control in forest nurseries has been primarily achieved through preplant soil fumigation with methyl bromide combined with chloropicrin (MBC, 67:33) at 392 kg/ha under a Quarantine Preshipment Exemption to the Montreal Protocol (Weiland et al, 2013b). The most common soilborne pathogens are those causing damping-off and root rot, such as those in the genera Pythium,Fusarium,and Weiland,Page 3,Crop Protection Cylindrocarpon (Dumroese and James, 2005;Stewart et al, 2011;Weiland et al, 2013a;Weiland et al, 2011;Weiland et al, 2013b). Typical symptoms of infection by these pathogens include chlorosis, stunting, fine root mortality, and in severe cases, seedling death.…”