Stripping of Soil-Applied Hexazione, Picloram, and Tebuthiuron for Loblolly Pine Site Preperation

Abstract

Herbicides were applied to prepare two upland sites for planting of loblolly pine (Pinus taeda L.) after clearcut harvesting: (1) picloram pellets, (2) hexazinone liquid, (3) a slurry of tebuthiuron soluble powder, and (4) following underplanting, a liquid formulation of picloram + 2,4-D was injected into residual hardwoods. The herbicides in treatments 1 through 3 were applied in 4-inch-wide parallel strips spaced 98 feet apart in April 1981. On a per-acre basis, the rates of application were 1.8 lb acid equivalent picloram, 1.5 lb active ingredient (a.i.) hexazinone, and 1.5 lb a.i. tebuthiuron. Vegetation on all plots was prescribe burned in August 1981, and the plots were planted in January 1982 with loblolly pine (Pinus taeda L.) seedlings. Planting rows were evenly spaced between the chemically treated strips. In treatment 4, all hardwoods 1 inch or greater in diameter at breast height (d.b.h.) were injected near groundline in April 1982. Although the competing plant cover varied somewhat among the four site preparation treatments, one growing season after the pines were planted, loblolly pine survival, height, and diameter growth were not affected by treatment at either site through five growing seasons. Evidently, stripping soil-active herbicides as a means of preparing loblolly pine planting sites is no better than single-tree injection of the larger hardwoods left after clearcut harvesting.

Citation

Haywood, James D. 1993. Stripping of Soil-Applied Hexazione, Picloram, and Tebuthiuron for Loblolly Pine Site Preperation. Res. Note SO-372. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 6 p.