Research Project Summary

Russian knapweed is a significant invasive weed that occurs throughout Colorado and Utah.  Because of its creeping root system and allelopathic root exudates it is often found in large monotypic infestations.  The objective of this project was to provide information about specific Russian knapweed management strategies along the Dolores River that would aid in efforts to improve the health of this important riparian area.  An abandon pasture along the river was selected for this field experiment.  A selective herbicide, Milestone™, and three different grass seeding techniques were used alone and in combination to determine the best approach to converting this Russian knapweed dominated plant community into one dominated by native perennial grasses.  Russian knapweed and grass responses were monitored 20 months after the initial treatments were established.  Milestone provided complete Russian knapweed control 20 months after application and this turned out to be the only management strategy necessary to change the plant community to one dominated by inland saltgrass (Distichlis spicata) and sand dropseed (Sporobolus cryptandrus), two important native grasses.  Efforts to establish perennial grasses by drill seeding, broadcast seeding and broadcast seeding followed by roller packing have not been successful to this point (18 months after seeding).  At this site and probably for many other sites along the Dolores River, using a single application of a selective herbicide (Milestone) provided an extended period of time where remnant native species could establish without Russian knapweed competition or the negative impacts from allelopathic root exudates.  This is outcome is very encouraging.

Project Objective: To examine the response of a Russian knapweed dominated plant community along the Dolores River to single and multiple Russian knapweed management strategies.