Vol. 54—2000 - NorthEastern Weed Science Society

MUGWORT CONTROL WITH CLOPYRALID AND HERBICIDE MIXTURES
A.O. Ayeni and BA
Majek'
ABSTRACT
Mugwort (Artemisia vulgaris) is a major perennial weed of field nursery in New Jersey
with limited chemical control options under grower's conditions. Two rates (X and 1.5X)
each ofclopyralid (Stinger) (9 & 14 ovA), clopyralid + 2, 4-D (Weedar 64) (9 + 16 & 14
+ 16 ovA), clopyralid + 2,4-D + dicamba (Millennium) (44 & 65 ovA), clopyralid +
dicamba + MCPA (Trupower) (44 & 65 ovA), and dicamba + MCPA + triclopyr
(Coolpower) (52 & 78 ovA) were applied for mugwort control at 4, 6, and 8 weeks after
planting (WAP). An untreated control was added for comparison. Herbicides were
applied with a calibrated greenhouse sprayer fitted with 8002VS-nozzle tip and operated
at 30 psi and 68 gpa. Mugwort was raised under greenhouse conditions (75 to 900P day,
60 to 70'F night, 14 tol6 h light) from 3- to 4-inch rhizome fragments planted in 2-gal
plastic pots filled with regular mix (2:1 v/v peat moss:vermicullite mix plus lime,
fertilizer, and micronutrients). The experiment was set up in four randomized complete
blocks. Mugwort control was assessed based on foliage dry weight (live portions only)
four to eight weeks after herbicide application as well as dry weight of regrowth five
weeks after top removal.
All herbicide treatments applied 4 WAP controlled mugwort 1000/0within four weeks
after treatment. With herbicide application 6 WAP, Trupower and Millennium controlled
mugwort more than 95% within six weeks after treatment while Coolpower, Stinger or
Stinger + 2,4-D caused 90 to 95% control. When applied 8 WAP, Millennium, Trupower
or Coolpower caused only 60 to 67% control four weeks after treatment and Stinger or
Stinger + 2,4-D killed less than 50% mugwort foliage. When observed for five weeks
after top removal, there was no regrowth from all herbicide treatments applied at 4 or 6
WA.Pexcept Coolpower applied 6 WA.Pat 52 ovA which produced regrowth with dry
weight 2.1% of untreated control. When mugwort was treated 8 WAP, Millennium
causedthe least regrowth of approx. 0.5% dry weight of untreated control followed by
Stinger + 2,4-D (2.2%), Trupower (3.8%), Stinger (4.1%) and Coolpower (48.5%).11 was
concluded that all the herbicides tested are effective for the control of 4- to 6-week old
mugwort at the rates evaluated, but for 8-week old mugwort stands, Millennium is the
most effective, followed by Stinger + 2,4-0, Trupower, and Stinger in that order.
Coolpower, a non-clopyralid containing herbicide mixture, is ineffective at 52 to 78 ovA
for the control of 8-week old mugwort stands.
1 Research Associate in Weed Science and Professor of Weed Science, Rutgers University, Rutgers Agric.
Res. & Ext. Ctr., Bridgeton, NJ 08302.
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