What Are The Risks In Forestry Herbicide Applications?

Background

Forest crops grown in the Southeastern U.S. are a major contributor to the social, evironmental, and economic well being of the region. The 13 Southeastern states from Virginia to Texas combined produce more industrial roundwood (unprocessed logs) than any other region in the world. The forests protect important watersheds, provide recreation, and add immeasurably to the beauty of our nation.

Southern pine, of which loblolly pine is a major component, comprises 31% of the region's forest area according to the Southern Forest Resource Assessment published by the U.S. Forest Service in 2002. The loblolly is well adapted for "intensive" management: seedlings are transplantable after one season in the nursery bed, they survive well under a wide variety of site conditions, and are genetically improved for fast growth and excellent form.

Production of southern pine forests over the past 40 years has come to rely heavily on herbicides to ensure successful establishment of plantations. Exploiting biological differences between pines and hardwoods, herbicides have been developed which act to suppress hardwoods with little or no effect on the pines. Carefully applied herbicides thereby greatly enhance pine plantation growth rates.

Forestry Objectives

The forestry community in the Southeast applies herbicides on an estimated 2 million acres per year according to the Southern Forest Resource Assessment (U.S. Forest Service, Southern Research Station, September 2002), or about 1 percent of the approximately 200 million acres of timberland reported in the Assessment. Nearly all of the applications are made on private land, a mixture of forest industry and non-industrial private properties.

Unlike agricultural operations where pesticides are applied annually on the same area, forestry operations in the Southeast are limited to one herbicide application, or 2-3 applications in cases of very intense management, over the life of a plantation spanning usually more than 30 years.

It is important to note the applications involve only herbicides. Applied at labeled rates, the chemicals are toxic only to plants. At the rates applied, they are not toxic to humans, wildlife, fish, or insects. Furthermore, a study conducted by the National Council for Air and Stream Improvement reveals that forestry herbicide application rates are typically 25% of the rates allowed on the herbicide labels.

Active ingredients used in forestry applications in the Southeast consist primarily of imazapyr, glyphosate, hexazinone, triclopyr, sulfometuron methyl, and metsulfuron methyl. All have passed rigorous U. S. EPA testing for toxicity and environmental fate, and are labeled for application to achieve forest management objectives.

Application equipment used in forestry is designed to control drift, and is used only during periods of stable weather conditions. Aerial application for forestry purposes is restricted to the use of helicopters. Aerial booms are configured to release large droplets in the 1,000 to 1,500 micron range, allowing the water-borne product to descend in a sheet for accurate placement, as opposed to a mist common in many agricultural operations. In most cases aerial application is guided by an onboard geographic positioning system and flow meter which record exact placement of the application on the face of the earth, including time, date, type and amount of material.

Herbicides labeled for forestry include label statements prohibiting application over water. Therefore, operations incorporate no-spray buffer strips along streams, ponds, and swamps containing standing water. These strips are wide enough to prevent migration of active ingredient to open water.

Aerial application is avoided during periods when the surface wind exceeds 5 MPH, when fog could capture spray droplets and move them off the target site, or immediately before or after a rain event which could wash the chemical off the target foliage.

Tract boundaries are clearly delineated prior to application to avoid off-site applications.

Check Us Out

The forest industry in Virginia has teamed with VDOF and the USFS to provide annual reports of forestry herbicide use in the Commonwealth to the VA Dept of Agriculture and Consumer Services. These reports document the number of acres over which herbicides were applied during the previous year, and the poundage of each active ingredient used.

Forestry activities applied a total of 68,000 pounds of active ingredients in 2002. By comparison, the Virginia Office of Environmental Education reports that more than 6.5 million pounds of pesticide active ingredients are used in Virginia each year.

Need more information?

Contact Dean Cumbia, Herbicide Spray Coordinator, 434.977.6555

Last modified 2007-07-12