Vol. 54—2000 - NorthEastern Weed Science Society

EFFECT OF HERBICIDE RATE, SEQUENTIAL HERBICIDE
TREATMENT, AND MOWING ON MUGWORT CONTROL
K. W. Bradley and E. S. Hagood '
ABSTRACT
Three field trials were conducted during 1998 and repeated in 1999 to evaluate mugwort
(Artemesia vulgaris L.) control with several herbicides and herbicide/mowing regimes. A
logarithmicsprayerwas utilizedin the ftrstfield trialto determineherbiciderates thatprovide
acceptablemugwortcontrol. Sequentialherbicidetreatments wereappliedto mugwortat 7-week
intervals in the second field trial to evaluate mugwort control following one. two. and three
herbicideapplications. In the thirdfield trial.the effect of sequentialmowing was investigated
by applying herbicides to mugwort regrowth following either one or two mowings. The
herbicides evaluated in all three field trials included 2,4-D amine, 2, 4-D ester, dicamba,
triclopyr, clopyralid, picloram, metsulfuron, glyphosate, and glufosinate. Pelargonic acid was
also evaluated as an addition to 2,4-D amine, glyphosate, and glufosinate in the logarithmic
sprayer trial. In the logarithmic sprayer trial, all herbicides except for metsulfuron were
evaluated at the rates of 8, 4, 2, I, 0.5, and 0.251b ai per acre. Metsulfuron was evaluated at an
analogous rate range with the highest rate being 0.56 lb ai per acre. In the sequential herbicide
and sequential mowing trials, 2,4-D amine, 2,4-D ester, and glyphosate were applied at 4.0 Ib ai
per acre, triclopyr and dicarnba at 2.0 Ib ai per acre, glufosinate at 1.5 Ib ai per acre, picloram at
1.0 lb ai per acre, clopyraIid at 0.251b ai per acre, and metsu1furon at 0.Ql121b ai per acre.
In the logarithmic sprayer trial, 100% control of mugwort was achieved with all rates of
picloram during both years. In 1998, all rates of clopyralid provided greater than 95% control of
mugwort. In 1999, however, slightly lower levels of control were observed at the 0.25, 0.5, 1.0
and 2.0 Ib clopyralid rates. The next highest level ofmugwort control was achieved with the 8,
4, and 2 lb glyphosate rates, which provided greater than 90% control in both years. Dicamba
also provided greater then 90% mugwort control at the 8 lb rate during both years. All remaining
herbicides generally provided unacceptable control of mugwort.
Sequential herbicide treatment trials conducted during both years revealed that only one
application of picloram was required to provide 100"10mugwort control. Additionally, two or
three treatments of clopyralid or glyphosate did not significantly enhance mugwort control
comparedto one applicationof these herbicides. In 1998. a secondapplicationof2.4-D amine,
2,4-D ester, dicarnba, or triclopyr significantly improved mugwort control, however a third
application of any of these herbicides was not warranted. Mugwort control was also
significantly improved with each additional application of glufosinate in 1998.
In the sequentialmowingtrial.two mowingsdid not significantlyenhancemugwortcontrolin
theclopyralid,dicamba,metsulfuron,picloram,ortriclopyrtreatmentsin eitheryear. In 1998, a
second mugwort mowing significantly improved mugwort control in plots treated with 2, 4-D
amine, 2, 4-D ester, glyphosate, and glufosinate. In 1999, however, the second mowing only
enhanced mugwort control in plots treatedwith 2. 4pDester and glufosinate.
'Grad. Res. Asst., and Prof., Dept. of Plant Path., Phys., and Weed Science, Virginia Polytechnic
lnst. and State Univ., Blacksburg, VA 24061
31