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be consulted for assistance in selecting appropriate chemical herbicides and treatment rates. Since these individuals are constantly updated on new products and weed control methods, it is a good practice to consult with them even after initial recommendations. Also included in this section are some locations of general concern to the Division. 1. Leafy Spwge - Euphorbia esula a. Mechanical Control -Tillage is very effective in controlling leafy spwge as is demonstrated by the fact that leafy spwge is not a problem on land under cultivation. Mowing may be effective in reducing infestations but generally will not eliminate the weed even under the most intensive mowing schedule. b. Chemical Control - A variety of herbicides have been proven to be effective in controlling leafy spwge. Recommended types depend on a variety of factors including location, cost, timing, etc. It is best to consult a local expert to assist in deciding what type and application rate to use. c. Biological Control -Sheep have been shown to effectively graze on leafy spwge especially in the spring before the spurge blooms. Once again this is similar to mowing and generally will not eradicate the infestation. However, combined with afollow-up herbicide program, this can be very effective. Another biological control which is quite new to Colorado is the leafy spwge hawk moth (Hyles Euphorbine). Control occws when the larvae of the hawk moth feed on the leaves of the spurge plant. 2. Canada Thistle - Cirsium arvense a. Mechanical Control- Canada Thistle can be controlled by repeated cultivation although it may take up to two years of cultivation at 10-15 day intervals to eliminate an infestation of thistle. Mechanical control is probably best when used in conjunction with herbicide treatments. Mowing is effective in reducing the spread of thistle and may reduce but not eliminate infestations. Mowing should be performed prior to or very shortly after bloom and repeated (at the same stage of growth) throughout the growing season. b. Chemical Control -The two most effective times for control of Canada Thistle with herbicides aze at the bud to eazly bloom stage in eazly summer and during regrowth in the fall. A variety of products aze available for use on thistle. An important point to keep in mind is that no matter what product is used, retreatment will be necessary. Once again a local consultant should be contacted for product and rate recommendations. 3. Musk Thistle - Carduus nutans L. a. Musk thistle can be cultivated for control. Repeated mowing prior to -I1-