PARENT SESSION
Poster Session 7: Invasive Species.
Monday, August 2 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Ecological benefits from the biological control of spotted knapweed.
Story, Jim1, Corn, Janelle*,1, White, Linda1, 1 Montana State University Western Ag. Research Center, Corvallis, MT
ABSTRACT- Biological control is an important component of exotic weed management, being useful in areas where application of pesticides poses unacceptable environmental risks, or where mechanical methods for control are not feasible. We will demonstrate the potential ecological value of noxious weed control with natural enemies, using spotted knapweed (Centaurea stoebe subsp. micranthos) as an example. Spotted knapweed is an invasive exotic perennial forb, introduced from Eurasia in the late 1800s, currently infesting 3 million ha of rangeland in Western North America. Herbicides, mechanical methods, and biological control techniques are used to control its spread. In plot experiments, we have found up to 15% mortality of spotted knapweed and biomass reduction in survivors of up to 75% after 2 years of attack by the root weevil Cyphocleonus achates. Field release sites with comparable C. achates populations have experienced declining density of spotted knapweed of 45% to 97% over 7 years. Across the temperature-dependent range limits of this biocontrol agent in Montana, reduction of knapweed biomass of this magnitude could reduce spotted knapweed dominance substantially across the current infestation. Knapweed decline should cause a proportionate recovery of the estimated $14 million in direct and $28 million in indirect annual economic losses due to knapweed infestations in Montana. Likewise, ecological benefits will be derived from restoration of plant community functions that have been compromised by spotted knapweed. Reduction of knapweed will result in increased livestock and wildlife forage, decreased surface water runoff and sedimentation, and increased plant species richness. Other biocontrol agents being used against spotted knapweed also have measurable impacts, so the benefits projected here from C. achates are likely conservative regarding overall benefits from biological control.
Key words: biological control, Cyphocleonus achates, invasive species, spotted knapweed