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Pathogen-based Biological Control of Grassy Weeds

Spotted knapweed is an aggressive invader of grassland ecosystems (photo by John M. Randall, TNC)
Spotted knapweed is an aggressive invader of grassland ecosystems (photo by John M. Randall, TNC)
Grass species number among the most insidious weeds worldwide, posing a serious threat both to agricultural production and natural systems. Progress on arthropod-based classical biological control of grasses has been fundamentally impeded by the perceived threat to global food security posed by insufficiently host specific graminivorous insects. In contrast, plant pathogens, including fungal pathogens of grasses, are considered to be intrinsically highly host specific. Many are already naturally occurring in the introduced range, creating the possibility of biocontrol using an augmentative or inundative approach. We have evaluated a suite of pathogens on the invasive annual grass weed Bromus tectorum (cheatgrass) as potential biocontrol agents. We worked extensively with the systemic, seedling-infecting castrating fungus Ustilago bullata (causal agent of head smut), and later with the seed pathogen Pyrenophora semeniperda (black fingers of death). Our current studies are focused on pathogens directly involved with cheatgrass ‘die-off’ or stand failure. While no one of these pathogens can effectively eliminate cheatgrass, our studies indicate that it may be possible to manipulate the community of naturally occurring pathogens on this host to create temporary stand failure that could provide a window for restoration.

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Susan Meyer

Dr. Meyer joined the research staff at the Shrub Sciences Laboratory in Provo, Utah, as Research Ecologist in 1987. Her early work focused primarily on the regeneration biology of native Intermountain shrubs, forbs, and grasses, in the context of the ecological restoration of shrublands. She has also worked extensively with the ecology and genetics of the exotic annual grass Bromus tectorum (cheatgrass or downy brome) and its relatives. For the past fifteen years she has been engaged in studies aimed at evaluating a range of pathogens that attack cheatgrass for their potential as biocontrol agents. More recently she has begun work on biocontrol using fungal pathogens for invasive buffelgrass (Cenchrus ciliaris).