Suppressing Tall Whitetop: Its Hard Work, But Possible
By Kathryn Barry
May 19, 2000
Rangeland overtaken by the weed known as tall whitetop, or
perennial pepperweed, can be restored to grassland, as
Agricultural Research Service scientists
in Reno, Nev., have shown for the first time.
The weed has become a nemesis of ranchers and land managers across
the West and in New England. The plant can grow eight feet tall in wet areas
along streams, rivers, ditches, irrigation canals and salty marshes.
Researchers in the ARS
Exotic and Invasive Weeds
Research Unit have explored a variety of pesticides--as well as grazing and
seeding strategies--to subdue the weed and have found an approach that works.
First, spray the area with 2,4-D. Unlike many other pesticides the
scientists tested, 2,4-D doesnt leave a residue in the soil that would
prohibit using the land for growing crops like alfalfa.
Second, plant either tall wheatgrass or robust needlegrass, a
competitive species under evaluation by ARS researchers in
Logan, Utah. Both of these
perennial grasses can outcompete tall whitetop if managed properly. The
needlegrass may be desirable because it is also a native plant. And unlike a
related plant known as sleepygrass, robust needlegrass does not
contain toxins harmful to animals.
A second year of limited 2,4-D application is necessary to help
get grasses established. Land managers may have to graze the area to minimize
stubble accumulation during the winter. Thats because large amounts of
stubble give voles and rabbits lots of places to hide from the hawks that
normally prey on them. Large rodent populations will eat the grass seed,
allowing tall whitetop to reinfest.