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Abstract. Eight herbicide treatments were applied by lowvolume basal applications and compared to hand cutting for the removal of Ailanthus altissima. Manual cutting of Ailanthus stimulated resprouting and increased overall stand density. Chemical control not only removed existing trees but also prevented resprouting. When evaluated 2 years after treatment, optimal control of Ailanthus was achieved with a combination of Garlon 4 and Tordon K herbicides. Garlon 4 at 20% v/v alone, Garlon 4 combined with Stalker, or Stalker herbicide alone controlled Ailanthus better than hand cutting but were not as effective as treatments containing picloram. Removal of Ailanthus resulted in a shift in herbaceous species to native species of the region without reseeding with naturally occurring herbs. Manual control of Ailanthus should be avoided in order to prevent proliferation. Herbicide control of Ailanthus is the preferred method of control because it successfully kills the trees and prevents resprouting. Because major Ailanthus infestations occur near roadways, access with a backpack sprayer should be achievable.
Key Words. Ailanthus; invasive exotic tree; native vegetation; Tordon K picloram; Garlon 4 triclopyr; Stalker imazapyr; tree-of-heaven; herbicide control; manual cutting; tree ecology; allelopathy.
Ailanthus altissima (tree-of-heaven) is an invasive exotic weed tree that has become established throughout North America. The state of Virginia, U.S., currently is experiencing a rapid invasion of Ailanthus along highways, utility rights-ofway, pastures, and disturbed forest sites. A recent survey of interstate highways in southwestern Virginia found that 30% of the mileage along the highways was infested by Ailanthus (Stipes 1995). Ailanthus forms pure stands that shade out herbaceous growth and decrease native plant diversity They also obstruct vistas along roadways as well as create a safety hazard by obstructing the view of drivers. A successful control method must be able to kill the Ailanthus stems and roots while allowing for the reestablishment of native vegetation on the site.
If ecological integrity is to be maintained in parks and other natural areas, invasive exotic species such as Ailanthus must be controlled within an acceptable limit. The purpose of this study was to test the effectiveness of herbicide tank mixes as low-volume basal applications on Ailanthus altissima. In the study the efficacy of several different mixtures of Garlon 4(R) (triclopyr ester) plus Tordon K(R) (picloram salt)...