Pesticide and Environmental Update
Challenging
Weed Meets its Match in Field Trials
In Oregon, California and other western states,
infestations of medusahead have marched across rangeland habitats like the
Genghis Khan of grasses. But at the base of Steens Mountain in
southwestern Oregon, a small but stubborn band of defenders--desert
wheatgrass plantings-- have held fast against the invader, offering hope
of a new, ecologically based approach to controlling it.
Agricultural Research Service (ARS) rangeland
scientist Kirk Davies is monitoring the Steens Mountain
"standoff" as part of a broader research effort at Burns, Ore.,
to develop new tools and strategies for land managers to use in
controlling medusahead, Taeniatherum caput-medusae. This invasive species
infests millions of acres there and in other western states. It has
decimated native plant communities, reduced forage quality, degraded
wildlife habitat and caused other harm, according to Davies, who works at
the ARS Range and Meadow Forage Management Research Unit in Burns.
He and ARS ecologist Roger Sheley and range
technician Aleta Nafus first established the desert wheatgrass, Agropyron
desertorum, in February 2006 as a dozen 49- by 33-foot bands on the
leading edge of a medusahead infestation near the foothills of Steens
Mountain. Beyond the bands lay undisturbed communities of sagebrush,
squirreltail, needlegrass and other native plants.
In June 2008, the team measured the density and
canopy cover of medusahead whose seed had managed to spread beyond the
desert wheatgrass barriers and become established in the plant
communities. Medusahead spread data also was collected from a dozen
barrier-free sites.
The team's analysis, presented in Oregon State
University's 2009 Field Day Report earlier this year, showed that native
plant communities without the barriers harbored more medusahead than those
with the barriers--a difference of more than 40-fold. Davies attributes
the reduction to the ability of wheatgrass to compete for soil resources
and potentially snare wind-blown medusahead seed.
Future research could focus on fine-tuning the
approach and ensuring the compatibility of desert wheatgrass with native
species--its "protectees." Ideally, the barriers would be
integrated with other measures, including prescribed grazing and judicious
use of herbicides.
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