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.~ f ` • • . ~ ' with Tordon 22K when applied at 0.25-0.5 lb ai/A anytime the weeds are actively growing. Spring would be good timing for their control with Tordon. Poison hemlock and cluster tarweed are best controlled with 2,4-D (although Tordon also should control cluster tarweed). Apply 2,4-D to poison hemlock at 2 lb ai/A in spring when the weed is in the early bloom stage. 2,4-D is registered for use right up to the water's edge (do not contaminate water with 2,4- D) and often this is where poison hemlock grows. For cluster tarweed control, apply 2,4-D at 1-2 lb ai/A (higher rate for very dense stands) in spring when weeds are relatively small. Sagebrush is effectively controlled with Spike 20P (common name tebuthiuron) made by Elanco. It should be applied at 0.5- 0.75 lb ai/A anytime (do not apply to snow covered ground) but, injury to desirable grass species is reduced when applications occur when grasses are dormant (e.g. in fall after grasses are dormant). Spike is taken up by the root system and works very slowly (it is a photosynthetic inhibitor) and normally sagebrush control is achieved in 2 to 3 years. Spike is registered for use in rangeland and non-crop areas. Unfortunately, Spike 20P requires special application equipment and in the past had to be applied by air. I understand that ground application equipment now is available. 2,4-D also will control sagebrush but the window of time for application is quite narrow and all plants are not at the same growth stage at the same time thus, some plants are not effectively controlled with 2,4-D. Banvel is another herbicide that I think you are familiar with and it will control Canada thistle, houndstongue, and does a good job on catchweed bedstraw. Rates and timings are covered in the Pest Control Guide and I will not reiterate them here. I do not have a current price list for any of these herbicides; however, 2,4-D will be the least costly to use per application. Unfortunately, Canada thistle would require repeat applications for several season with 2,4-D and would not be the most cost effective material. Tordon or Telar, although much more expensive initially, would be more cost effective over time because control can be achieved for several seasons with a single application. It is important to realize that Canada thistle will not be eradicated with a single application of any herbicide. Spike also is expensive but the control realized makes it cost effective. I hope this information is what you were seeking. If anything is not clear or you need further information please contact me at 491-7568 or write to me at 115 Weed Research Lab, Colorado State University, Ft. Collins, CO 80523. Sincexxely~~ ~/ l .•,•' l . /~ } Jam.- ~ _, 1~c K. George Beck, Ph.D. Extension Weed Specialist cc: Jim Stanko Routt County Extension