Description:
Johnsongrass is
an erect, perennial grass that ranges from three to ten feet tall.
The stems are solid with prominent, swollen nodes. The leaves are
alternate, and range from 12 to 30 inches long and 1⁄2 to
1 inch wide, with a noticeable white mid-vein. The stem terminates
in a reddish inflorescence of an open, pyramid shaped panicle, from
6 inches to 24 inches long. At each joint of the panicle, two or
three branches occur. The flowers, or spikelets, are in pairs at
the lower end of this flowering stalk, and in threes at the upper
end. The pair includes one spikelet with male flowers, and it has
short stalks.
- Mechanical:
Repeated tillage is an effective control strategy. Smaller rhizome
fragments are brought to the soil surface, where they are susceptible
to desiccation and freezing winter temperatures. Shoots developing
from these rhizome fragments are less vigorous (Lolas and Coble
1980 and McWhorter and Hartwig 1965 as cited in Hartzler et al.
1990). If cultivation is not repeated, the infestation can spread,
since broken rhizome segments can produce roots and shoots (Fischer
et al. 1985). Fields cultivated every four to five weeks offer
the best results, and the recommendation is to used several tools
- one to cut the rhizomes into small sections, and another to
bring the fragments to the soil surface.
- Biological:
None known.
- Herbicide:
Herbicides will control the upper plant, but they do not always
translocate to the dormant buds found on the rhizomes, and these
buds remain viable and later germinate (McWhorter 1972a). Preemergent
treatment will control seedlings, but not established stands.
Ecotypes of Johnsongrass may be responsible for variable control
rates of foliar-applied herbicides (McWhorter 1971). For site
specific control information, refer to the annually updated Pacific
Northwest Weed Control Handbook. Refer to the State
Noxious Weed Control Board site
For More Information:
Detailed information about Johnsongrass
is available at the Washington State Noxious Weed Control Board
Web Site. |
