Gray Rabbitbrush Control
Following Applications of
Redeem R&P and Crossbow
Herbicides
December 2000

A. Wayne Cooley (deceased)
former Area Extension Agent
Tri River Area
CSU Extension


TABLE OF CONTENTS

Introduction
Objective
Materials and Methods
Results and Discussion
Diagram I: Gray Rabbitbrush Control Following Applications of Redeem R&P and Crossbow Herbicides, LeValley Ranch

Introduction

Gray rabbitbrush (Chrysothamnus nauseosus (Pallas) Britt.) is a strongly scented perennial plant that has many branches. The stems are silky or white woolly covered and range in height from 2 to 4 feet. The flowers are in large clusters at the tips of the stem and yellow in color.

Gray rabbitbrush, also called rubber rabbitbrush, is one of at least 12 native species of Chrysothamnus that occur mainly in the western U.S. They grow well in dry soils and are often associated with sagebrush. Gray rabbitbrush is an invader and its presence in dense stands indicates over-grazing. Plants rate low in palatability but sheep and wildlife will eat the plant. Indians used gray rabbitbrush as chewing gum, for yellow dye, tea, and for medicine.

Control of this undesirable shrub is difficult due to its ability to re-sprout from the crown after being sprayed or burned.

Objectives

The objective of this test was to determine the level of Gray rabbitbrush control when broadcast applying Redeem R&P and Crossbow herbicides. Both herbicides contain active ingredients that have shown to be effective on various brush species. Both herbicides are federally registered for use on pasture and rangeland.

Materials and Methods

Broadcast applications were made using a CO2 plot sprayer with a 3 nozzle boom (5 foot spray swath) mounted on a Honda ATV. Nozzles were on 20 inch spacings, containing Tee Jet 8002 spray tips. Applications were made at 4 mph with a pressure of 28 psi at the CO2 tank. The sprayer was calibrated and delivered 11.6 gpa of solution at the above speed, pressure, nozzle spacing, and spray tips.

Redeem R&P was applied at 4 pts/A and Crossbow was applied at 3 qts/A to Gray rabbitbrush as a broadcast application on June 12, 2000. Both herbicides had the addition of X-77 surfactant at a rate of 1 qt/100 gallons of spray solution. The environmental conditions (10:15 a.m.) were air temperature 75 F, relative humidity 24 percent, wind 0 mph, and clear skies. Applications were completed at 11:15 a.m.

The Gray rabbitbrush was actively growing and ranged in height from 10 to 36 inches. See plot diagram for size and treatment location.

Results and Discussion

The Redeem R&P and Crossbow treated areas were observed on June 23, 2000 and pictures were taken of the symptoms. The Gray rabbitbrush was turning yellow (chlorosis) in both the Redeem R&P and Crossbow treated areas.

redeem
Redeem R&P

The success of the herbicide treatments will be determined during the 2001 growing season by evaluating the amount of regrowth that occurs from each treated area.

Diagram I: Gray Rabbitbrush Control Following Applications of Redeem R&P and Crossbow Herbicides, LeValley Ranch

Colorado State University, U.S. Department of Agriculture and Delta, Mesa, Montrose & Ouray Counties cooperating. Extension programs are available to all without discrimination. No endorsement of products is intended nor is criticism of products mentioned.


Page Maintained by Norraine Harvey, Administrative Technician
Colorado State University - Tri River Area
Mesa County Extension
2775 Highway 50, P.O. Box 20,000-5028
Grand Junction, CO 81502-5028