Habitat and Life History
Johnson grass is a perennial, noxious weed native to the Mediterranean region
and was first identified in Kansas in 1880.
It has moderate forage value, however
hydrocyanic acid formed in the plant under frost or drought stress renders it
poisonous to livestock.
It spreads rapidly by seed or its vigorous rhizome structure.
A single mature plant may produce over 80,000 seeds and 200 feet of rhizomes.
The seed can remain viable in the soil for up to 25 years and will begin producing
lateral rhizomes 6-9 weeks after germination.
Crop Losses
Johnson Grass is one of the most costly
weeds with which farmers must contend.
It costs them millions of dollars each year
in lost crops, poor quality
grain and lower crop yields. Five Johnson Grass stems per .0001 acre reduces
soybean yields by 4.2%; 50 stems reduce yields by 23% and 340 stems, 88%.
One Johnson Grass head per 3.3 feet of grain sorghum row reduces yield by
52 pounds per acre while 50 heads per 3.3 feet reduce yields by 50%. A single
plant at maturity may produce over 80,000 seeds and more than 212 feet of
rhizomes. Johnson Grass seed can remain viable in the soil for up to 25
years.
Prevention of Spread
Preventing seed production and its spread is of primary importance. New infestations
of Johnson Grass may be reduced by planting Johnson Grass-free seed, using
livestock feed that is free of Johnson Grass seed, and cleaning machinery
before leaving infested fields.
Cultural Control Practices
Control of Johnson Grass shall mean preventing the production of viable
seed and destroying the plant's ability to reproduce by vegetative means.
Control may be achieved by chemical, cultural or mechanical means, or by
combinations of these methods.
Cultivation may begin any time during the growing season and shall cut off
all the weed plant at each operation (use duckfoot or blade type implement).
Cultivations shall be 3 to 5 inches deep at intervals of 14 to 18 days.
When the plants have so weakened that they emerge more slowly, the cultivation
intervals may be extended to such time as will permit the plants to grow
not more than ten days after each emergence of the first plants, but not
to exceed intervals of three weeks. Cultivation shall be continued until
the weeds have been eradicated or suppressed to such an extent that remaining
plants may be more economically destroyed by application of approved chemicals
to individual plants or by hand cultivation.
In yards, flower gardens, lawns, and around trees and shrubbery, hoeing
and other effective means of thoroughly cutting the weeds at regular intervals,
not to exceed 14 days during the growing season, shall be construed as intensive
cultivation.
Close grazing or mowing at 2 or 3 weeks intervals through the growing season
and followed by late fall plowing to expose the root stalks through the
winter is a accepted control practice.
Approved Herbicides
The following herbicides may be cost-shared with landowners. Other products
labeled and registered for use on this noxious weed in Kansas may be used
in accordance with label and directions but are not available for cost-sharing.
- Generic Roundup - 2.5 gallon containers
- row crops and cereal grains
- fence rows
- ditch banks
- feedlots and waste areas
- CRP
- LIMIT 10 GALLONS WITHOUT A PROPERTY INSPECTION
Kills Johnson Grass and all other green vegetation with no
residual
- Roundup Dry Pak - small quantity
containers
- vegetable gardens and flower beds
- ditch banks
- fence rows
- each dry pak or packet makes one gallon of 2% spray
solution
Kills Johnson Grass and all other green vegetation with no
residual
- Mechanical / Cultural
- fall tillage and cold weather will reduce Johnson
grass
- early and continuous grazing can eradicate Johnson
grass
- repeated mowing will eliminate seed production and
reduce plant vigor
- the county has a pipe wick applicator available
for landowner use
Factors for Best Control
- Use properly calibrated equipment.
- Timely application
- Follow up to treat field borders, skips, escapes and to control
seedlings.
