Economic Evaluation of Scotch Thistle Suppression

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Abstract
Economic evaluation of Scotch thistle (Onopordium acanthiumL.) infestation of grazing land in northeastern California revealed potential annual losses to ranchers approximated $10.20/A for wet meadows, $6.70/A for wheatgrass (Agropyronspp.) stands, and $3.40/A on downy brome (Bromus tectorumL.) rangelands. Annual application of 0.06 lb/A of 4-amino-3,5,6-trichloropicolinic acid (picloram) provided the most economical ($3.57/A) means of suppressing Scotch thistle. Annual application of 0.06 lb/A also introduced less picloram into the environment than less frequent application of higher rates. Application of picloram to suppress Scotch thistle limits management options and reduces potential land values.