Pesticide Use and Risk Reduction in Rights-of-Way Vegetation Management

Most industrial herbicides used for vegetation control in rights-of-way are very low in toxicity; in fact, much lower than the petroleum products necessary to power the equipment used for cutting brush. Therefore, the use/risk reduction strategy for electric utilities is aimed at minimizing the amount of active ingredient of a particular product (or products) per acre rather than reducing the total volume of products used. Lower use per acre is both environmentally responsible and economical: by utilizing only the amount necessary to control vegetation, risks are minimized and material costs are reduced.

Most initial right-of-way vegetation applications are made using non-selective techniques. Non-selective applications are also utilized for maintenance where brush heights and/or densities are high. Mechanized applicators are frequently used for these applications.

In subsequent applications or in applications where brush heights and densities are low to moderate, low volume foliage or basal applications are generally utilized. Carriers for low volume applications are normally water for foliage treatments while synthetic or natural penetrants are used for basal treatments. These applications are referred to as "low volume" because of the lower quantities of water or penetrants used to dilute and carry the chemicals to the plant. Low volume techniques employ garden-type hand-pump or motorized applicators to apply the herbicide mixture at very low rates and pressures.

The key to reducing the amount of herbicide applied per acre is the use of selective applications; i.e., treating only those plants that are capable of growing tall enough to threaten power lines and to leave low growth plants (shrubs, herbs, grasses) untreated. This can be accomplished with any ground application method, but the selective nature of the treatment remains the same. As a result, active ingredients of herbicide applied per acre are minimized and risks are reduced.

Selective applications can also result in reduced herbicide usage as a result of species composition changes from incompatible plant species to compatible plant species. Future herbicide treatments to the same areas will require lesser amounts of herbicides due to the selective nature of the application combined with fewer target stems.

The use of non-active adjuvants can also contribute to reduced volume and, therefore, risk. Adjuvants can improve efficacy and adherence to the target plants resulting in less material being required for control, less runoff from the plant leaf surface and reduced potential for volatilization.

During applications the potential for exposure is only to the diluted herbicide mixture and that exposure is brief since workers apply the solution and then leave the area. After the herbicide is absorbed by the plant, direct exposure is virtually negligible. Any herbicide not absorbed by the plant is rapidly biodegraded by micro-organisms or light. Considering the low toxicity, rapid uptake and rapid biodegradation of most modern herbicides, re-entry times are not significant for these types of application.