Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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HERBICIDE COMPARISON IN WET BLADE APPLICATIONS FOR SWEET GUM,
TULIP POPLAR, AND RED MAPLE CONTROL. A.R. Post and J.C. Neal, North
Carolina State Univ., Raleigh, and C.A. Judge, BASF, Research Triangle Park, NC.
ABSTRACT
Roadside and right-of-way vegetation must be managed to maintain motorist
visibility and safety, and to prevent vegetation from interfering with utility lines.
Traditionally, the department of transportation has used mowing or broadcast sprays of
broad-spectrum herbicides to control woody vegetation on roadsides and right-of-ways.
Mowing provides only temporary suppression and must be repeated every one to three
years. Broadcast sprays are undesirable on right-of-ways due to the potential for offtarget
impacts. An alternative herbicide application strategy is the treatment of cut
stems using "wet blade" application systems such as the Diamond Wet Blade.
However, little research has been conducted to compare the effectiveness of wet-blade
herbicide applications on woody vegetation. This study compared the efficacy of wet
blade applications of four herbicides at five concentrations each on three common,
roadside woody weeds -- sweet gum (Liquidambar styraciflua), tulip poplar
(Liriodendron tulipifera), and red maple (Acer rubrum). The treatments included
triclopyr (Garlon 3A), metsulfuron (Escort), and glyphosate (Rodeo) at 50%, 25%, 10%,
5%, and 1% and imazapyr (Arsenal) at 10%, 5%, 2.5%, 1%, and 0.5% by volume in
water. Trees were plantation-grown for this study to ensure uniform age at application.
Five ml of each treatment solution was applied to the cutting blade of lopping shears
and stems were cut approximately 10 cm above the ground. Treatments were applied
November 30, 2005 in a randomized complete block design with 4 replications of each
species. Re-growth was measured August 30, 2006. No treatment resulted in 100%
mortality of all species. Sweet gum was 100% controlled by 50% triclopyr and 10%
imazapyr; 25% triclopyr and 1% imazapyr each provided >90% on sweet gum. Red
maple was controlled 100% by 10%, 2.5% and 1% imazapyr; and >90% by 0.5%
imazapyr. No treatment provided 100% mortality of tulip poplar. Greatest tulip poplar
control was observed with 2.5 to 10% imazapyr, and 10% to 50% glyphosate. Triclopyr
did not control tulip poplar. This study suggests that combination treatments may be
required to achieve broad-spectrum woody vegetation control with wet blade
applications.
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Acknowledgement and Disclaimer: this research was funded by a grant from the NC
Department of Transportation. The authors are responsible for the facts and the accuracy of the
data presented herein. The contents do not necessarily reflect the official views or policies of
either the North Carolina Department of Transportation or the Federal Highway Administration
at the time of publication. This report does not constitute a standard, specification, or
regulation.
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