Herbicides including Telar, Escort and Cimarron are effective from the bud growth stages through the later stages of the plant’s maturity (before the weed begins to turn brown). Applications should be made at a rate of 1 ounce per acre.
Spotted Knapweed
The most effective treatments of spotted knapweed are made early in the plant’s lifecycle (rosette to early bolt stages). Milestone is an effective general use herbicide and should be applied at 5 to 7 ounces per acre. Infestations should be reported to the Weed Mitigation Department.
Yellow Starthistle
Herbicide applications should be made prior to seed production. Milestone can be effective at 5 ounces per acre and should be coupled with pulling or digging to remove plants from the site. Infestations should be reported to the Weed Mitigation Department
Purple Loosestrife
Herbicide must be applied prior to flowering. Garlon 3A at 1 to 2 quarts per acre or Habitat at 1quart per acre should be used based on the surrounding plant life. Seed heads should be cut and removed if the plants are allowed to flower. Infestations should be reported to the Weed Mitigation Department.
Yellow Toadflax
Infestations are most effectively treated with chemical mixtures that include restricted use herbicides (Tordon). Late summer and early fall is the optimum treatment window. Infestations should be reported to the Weed Mitigation Department
Russian Knapweed
Effective treatments can be made with Milestone at 4 to 6 ounces per acre. Applications can be made when 10% of the plants’ buds are blooming (summer) and throughout the winter (the ground should be visible and relatively dry).
Diffuse Knapweed
The most effective treatments of diffuse knapweed are made in the rosette to early bolt stages (spring and fall). Milestone is an effective general use herbicide and should be applied at 5 to 7 ounces per acre. Infestations should be reported to the Weed Mitigation Department.
Tamarisk
Cut-stump and basal bark treatments can be made throughout the year and foliar applications can be made between late spring and early fall. Garlon 4 or Habitat can be used for foliar applications. The Weed Mitigation Department recommends using Pathfinder for basal bark and cut-stump treatments.
Using Herbicides
All treatment methods are recommended because of their effectiveness and relative universality. As herbicide chemistry often changes, labels should be followed explicitly. Site ecology including the presence of other weed species may make the use of other herbicides more practical. Consideration of biological, cultural and mechanical controls alone, or in conjuncture with these treatment methods is recommended.