Optimum Treatment Rate for Tebuthiuron on Rangeland Infested with Sand Shinnery Oak

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Over 4.2 billion pounds of beef were produced in Texas with a value of over $1.2 billion in 1971, the greatest for any of the fifty states. Texas production of range livestock is limited by the availability of rangeland. In 1967, over 53% of the land area in Texas was classified as rangeland and 82% of the grasslands of the state was infested with undesirable woody plants (Osborn and Witkowski). Brush problems, for the most part, are brought on by man himself. Brush is a problem because it competes with grasses needed for livestock grazing. Sand shinnery oak typically has a large root system which is extremely hard to kill. Top kill of the sand shinnery oak is relatively easy, but the root kill is usually low. Total plant kill from aerially applied liquid herbicides is rare. Following top growth disturbance new shoots may arise from buds along with the more shallow rhizomes, resulting in only temporary control. Tebuthiuron has been used on sand shinnery oak, and rates above 3 kilograms per hectare essentially cleaned out the plant community. Grass yields increased dramatically following oak kill, but judicious grazing management with occasional deferment is needed to retain a healthy plant cover (Pettit). At the end of a third growing season after treatment with tebuthiuron at different treatment rates of active ingredient per acre, it was found that oak was reduced as the rate of herbicide increased (Jones and Pettit). Tebuthiuron at a rate of 0.4 kilogram per hectare or greater converted the sand shinnery oak into a mid-grass prairie. At these rates, over 80% of the sand sagebrush was killed and the yield of sand shinnery oak was reduced by at least 90% (Jones). One goal of a rancher is to utilize his land at the highest productive capacity. Today, more ranchers are achieving this goal through initiating some type of brush control program. Chemical control of sand shinnery oak through aerial application of tebuthiuron has been introduced as an effective brush control program. Little economic analysis has been done on the costs and returns associated with aerial application of tebuthiuron; therefore, this paper attempts to explain those factors associated with determining the optimum treatment rate for aerially applied tebuthiuron on sand shinnery oak. The specific objectives of this paper are (a) to develop an equation which estimates the total grass production associated with different treatment rates, (b) to estimate the annual revenue and costs associated with the application of tebuthiuron, and (c) to estimate the optimum treatment rate to the Texas High Plains rancher under current economic conditions in the livestock market and application costs.