Chemical Control of Big Sagebrush and Its Effect upon Production and Utilization of Native Grass Species

Abstract

A S EARLY AS 1946, a limited study conducted in Oregon (5) showed .t big sagebrush (Artemisia tridentata Nutt.) to be susceptible to the sodium salt of 2,4-D. Cornelius and Graham (3) stated that big sagebrush was highly susceptible or hypersensitive to 2,4-D. Kissinger, Hull and Vaughn (7), reporting on experiments conducted at the Beaver Rim area near Lander, Wyoming, found that the isopropyl and amyl ester of 2,4,5-T consistently gave higher kills for a given amount of chemical. One pound acid equivalent (hereafter referred to as pounds acid) of 2,4,5-T usually gave somewhat higher kills than two pounds acid equivalent of 2,4-D. Hull and Vaughn (4) stated that the type and amount of chemical which killed two-thirds or more of the brush plants varied with the carrier and the season. The butyl ester form of 2,4-D gave better results than mixtures of 2,4-D and 2,4,5-T or the contact sprays. Hyder (6), working in Oregon, stated that butyl ester of 2,4-D gave the best control for the money, even though the growth regulator, 2,4,5-T, killed more brush. Colorado workers (1) showed that volatile esters of 2,4-D gave more economical control of big sagebrush than the low-volatile esters. The herbicide 2,4,5-T made a poorer showing as an economical means of control, was less effective than 2,4-D, and more costly. Bohmont (2), observing the effects of chemicals 75 days after treatment, noted that a low-volatile (tetrahydro furfural) ester of 2,4-D, at two pounds acid per acre, caused the most observable toxicity. While 2,4,5-T treatments suppressed seed head development, the plants partially recovered and seed heads formed during the growing season, compared to the 2,4-D treatment which prevented seed heads from forming. Increase in production of native forage has been reported on all sites where chemical control has been used. Average air-dry herbage production near Lander (7) showed 222 pounds per acre on untreated land; 490 pounds per acre with 58 percent sagebrush control; 553 pounds with 66 percent sagebrush control; and 645 pounds with 97 percent sagebrush control. Native grass production, on an experimental area near Lander, was increased two to three times by killing 60 to 97 percent of the sagebrush. The increased production and more accessible forage supply on the sprayed areas were utilized almost twice as heavily as on unsprayed areas. Bohmont (2) stated