Wednesday, March 18, 2009

Cut vs. Herbicide For High Power Line Vegetation Management

The Center believes manual and mechanical cutting of trees and other vegetation underneath high power line rights of way (ROW) are superior to herbicide use because cutting creates green jobs. Moreover, although we have a deep appreciation for the effectiveness of a combined cut and herbicide regimen, the fewer amounts of chemicals used in nature, the better. A panel of 23 experts from the International Society of Arboriculture (ISA) is crafting a best management practice (BMP) for integrated vegetation managment (IVM) to servce as a field guide for front-line supervision, as well as an aid for managers to help facilitate planning.

Managers have a variety of control methods from which to choose, including manual, mechanical, herbicide and tree-growth regulators, biological and cultural options. Manual methods employ workers with hand-carried tools, including chain saws, handsaws, pruning shears and other devices to control incompatible vegetation. The advantage of manual techniques is that they are selective and can be used where others may not be. However, manual techniques can be inefficient and expensive compared to other methods. Mechanical controls are done with machines. Although mechanical control methods are efficient and cost effective — particularly for clearing dense vegetation during initial establishment or reclaiming neglected or overgrown ROW — they can be nonselective and disturb sensitive sites.

Many utilities believe tree-growth regulators and herbicides are essential for effective vegetation management. Tree-growth regulators are designed to reduce growth rates by interfering with natural plant processes. They can be helpful by reducing the growth rates of some fast-growing species where removals are prohibited or impractical. Herbicides control plants by interfering with specific botanical biochemical pathways. Herbicide use can control individual plants that are prone to resprout or sucker after removal. When trees that resprout or sucker are removed without herbicide treatment, dense thickets develop, impeding access, swelling workloads, increasing costs, blocking lines of site and deteriorating wildlife habitat. Treating suckering plants allows early successional, compatible species to dominate the ROW and out-compete incompatible species, ultimately reducing work. (Transmission & Distribution World, July 2007)

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