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

Authors: Weiland, Gerald - Jerry; LITTKE, WILLIS - Weyerhauser Company; HAASE, DIANE - Forest Service (FS)

Submitted to: California Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2013
Publication Date: 8/12/2013
Citation: Weiland, G.E., Littke, W.R., Haase, D.L. 2013. Forest nurseries face critical choices with the loss of methyl bromide fumigation. California Agriculture. 67(3):153-161.

Interpretive Summary: Forest nurseries in the western United States have relied for decades on methyl bromide for the control of soilborne pathogens affecting bareroot tree seedlings. However, increased state and federal regulations have led to a substantial decrease in MB use, and eventually it is expected that the fumigant will no longer be available for use in tree seedling production. As a consequence, a number of studies have investigated other fumigants and disease management approaches for their ability to reduce pathogen populations and still produce quality, disease-free tree seedlings. Unfortunately, a number of these disease management strategies do not provide the same level of broad spectrum control as methyl bromide. Therefore, a greater knowledge of the identity, biology, and ecology of the pathogens in the forest nursery industry will be necessary in order to successfully reduce plant pathogen populations below damaging levels. Here, we review the forest nursery disease management practices that have been evaluated as alternatives to methyl bromide fumigation. We also identify knowledge gaps where additional research is needed in order to optimize disease control and assist the industry’s transition away from methyl bromide. In the future, an integrated approach combining nonfumigant methods with fumigation may provide the best strategy for the management of soilborne diseases.

Technical Abstract: Forest nurseries in the western United States have relied for decades on methyl bromide for the control of soilborne pathogens such as Cylindrocarpoin, Fusarium, and Pythium species that affect bareroot tree seedling production. However, increased state and federal regulations have led to a substantial decrease in MB use, and eventually it is expected that the fumigant will no longer be available for use in tree seedling production. As a consequence, a number of studies have investigated alternative fumigant chemistries, application rates and methods, as well as nonfumigant approaches, for their ability to reduce soilborne pathogen populations and produce quality, disease-free tree seedlings. Because a number of these disease management strategies have not provided the same level of broad spectrum control as methyl bromide, a greater knowledge of pathogen identity, biology, and ecology will be necessary to successfully reduce plant pathogen populations below economic threshholds. Here, we review the forest nursery disease management practices that have been evaluated as alternatives to methyl bromide fumigation. We also identify knowledge gaps where additional research is needed in order to optimize disease control and assist the industry’s transition away from methyl bromide. In the future, an integrated approach combining nonfumigant methods with fumigation may provide the best strategy for the management of soilborne diseases.