Darwin B. Nielsen

Economic feasibility of controlling tall larkspur on rangelands.

Larkspur (Delphinium spp.) poisoning of cattle poses a serious economic problem on many western rangelands. Losses varied from 1.5% to 12.3% of the grazing cattle over a 15-year period on the Manti Canyon grazing allotment. Three herbicides and different application methods were compared for control of tall larkspur. The 3 herbicides were: glyphosate [N-(phosphonmethyl) glycine]; picloram (4-amino-3,5,6- trichloro-2-pyridine carboxylic acid); and metsulfuron 2[[[[(4-methyoxy-6-methly-1,3,5-triaxin-2-yl) amino] carbonyl] amino] sulfonyl] benzoic acid. A boom type sprayer and a carpeted roller applicator were tested for the selective herbicides. Spot treatment and backpack sprayers were tested for the nonselective herbicide (metsulfuron). The internal rate of return was used to evaluate the economic feasibility of each alternative control method. A treatment was considered economically feasible if the internal rate of return was equal to or higher than the cost of borrowing money. Each treatment was evaluated for an assumed cattle death loss of 4.5% and 2.25%. A 10-year life was considered for each treatment. All of the herbicides and application methods tested were economically feasible. The internal rates of return varied from 14.23% to 133.38%. An internal rate of return above 100% occurs when the benefits in a single year exceeds the total cost of control. The cost of herbicides have increased considerably over the past few years, but they can still be used economically if treatment results in death loss reductions described in this study.