United States Department of Agriculture
NATURAL RESOURCES CONSERVATION SERVICE
Invasive Species Technical Note No. MT-11
Ecology and Management of Perennial Pepperweed [
Jim Jacobs, NRCS Invasive Species Specialist, Bozeman, Montana
Jane Mangold, Restoration Ecologist, USDA, Agricultural Research Service, Burns, Oregon
Perennial pepperweed infestation.
Photo by Michael Carpinelli.
Perennial pepperweed, also called tall whitetop and often confused with whitetop (
), is a rhizomatous perennial weed threatening riparian areas, irrigation ditches, and
floodplain meadows in Montana.
This weed in the mustard family (Brassicaceae) spreads by
creeping roots and rhizomes, and prolific seed production.
Found most often in seasonally
flooded areas, perennial pepperweed can also spread to upland and rangeland sites, and it is
adapted to salt-affected soils.
It can form dense patches that compete with crops, forage plants,
and riparian plants (see Figure 1).
Infestations reduce crop yield and increase production costs,
reduce livestock carrying capacity, and its control is costly.
Perennial pepperweed is native to southeastern Europe and western Asia.
The first record of
perennial pepperweed in Montana is from Gallatin County in 1935 along a roadside near
By 2002 it had been reported from 17 counties (
) with a
total of 2,750 acres infested.
In Montana it has been found along roadways, railroads, the
Missouri River, irrigation ditches, in winter wheat, alfalfa, Conservation Reserve Program,
pastures, on dry hillsides, and in rangeland.
Perennial pepperweed is ranked as a Category 2
noxious weed in Montana, meaning it is currently present and believed to be rapidly spreading
from existing infestations.
Perennial pepperweed can be temporarily suppressed using herbicides that contain metsulfuron,
chlorsulfuron, or imazapic as active ingredients. Long-term herbicidal control requires repeated
Cattle, sheep, and goats will graze perennial pepperweed, but the effects on