Introduction

Ailanthus (Ailanthus altissima), also known commonly as tree-of-heaven, is a widespread invasive exotic tree species in the eastern United States. The tree is native to China and had been planted extensively as an ornamental tree in the 19th century. Ailanthus tolerates a wide variety of environmental conditions (Miller, 1990), although it is intolerant of shade (Grime,

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1965). It can spread rapidly from both seeds and sprouts (Miller, 1990). Ailanthus is also produces allelopathic compounds (Mergen, 1959; Heisey, 1990; Lawrence et al. 1991) which may advance its spread into forests.

Trees store carbohydrates in the stem and roots during the dormant season and cutting hardwood tree species during the growing season compared to the dormant season has been shown to reduce sprouting vigor (Kays et al., 1988). Manual cutting of ailanthus has been shown to stimulate resprouting and increase overall stand density (Burch and Zedaker, 2003). Herbicide application to freshly cut stumps can control or prevent resprouting (Zedaker et al., 1987). Since cutting of trees is labor intensive and damage to residual vegetation or property could occur during felling, an alternative for killing ailanthus trees with felling is basal bark application (Burch and Zedaker, 2003). This control method uses an oil-penetrating formulation of a systemic herbicide applied to the bark, which translocates throughout the tree.

With either herbicide application method, the timing of application during the growing season to achieve the best control is uncertain. On one hand, manual cutting or application of herbicides to deciduous tree species during the spring may be effective because trees have recently exhausted their carbohydrate reserves after refoliation. On the other hand, fall application of herbicide treatments may provide more effective control because of movement of photosynthate in trees towards the roots for winter storage will increase the amount of a systemic herbicide translocated to the roots, increasing the likelihood of root mortality.

A study was initiated in 2003 to compare the efficacy of herbicide application method (cut stump application vs. basal bark treatment) and season of application (spring vs. fall) for controlling ailanthus on the campus of Ferrum College, Ferrum, Virginia, USA.

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