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Management of Houndstongue
Houndstongue is toxic to livestock. This plant contains alkaloids that cause liver cells to stop producing. Animals may survive for six months or longer after they have consumed a lethal amount of the plant. Although most animals will avoid houndstongue in the field, if even a small portion of a houndstongue leaf, for example, were to be included in hay, the animal will not avoid it. In this situation, there have been reported cases in Larimer County of death to livestock. This plant is not native to Colorado or the United States. The leaves are rough and resemble a hound's tongue.
Mechanical Control
Due to the rhizomes of this perennial weed, mechanical control provides little or no control. In addition, the areas where houndstongue tends to grow (i.e. wetlands) are impractical for tillage. Research from the University of California has shown that mechanical top removal treatments do not reduce houndstongue densities. Research from Colorado State University showed that handpulling or mowing controlled only 4% and 5% of houndstongue.
Chemical Control
In general, effective chemical control requires multiple applications. Timing and application rate are crucial for successful control. Again, application rate is critical; MORE DOES NOT NECESSARILY MEAN BETTER CONTROL. Always read the label when applying an herbicide. The label will be able to tell you how much to apply per acre. If you have any confusion as to how much chemical to apply to your tank, please call our office and we'll assist you.
Houndstongue can be controlled by the chemical imazapic. Brands of herbicides that contain this chemical are Plateau and Oasis. These chemicals can be applied as either pre- or post-emergent. They should be applied at 8-12 ounces per Acre. No more than 12 ounces/Acre of Plateau should be applied per year. These herbicides can be purchased at an agricultural products supplier (please check the yellow pages for specific stores).
Biological Control
No effective agents are known for Colorado at this time, however, research in this area persists.
Cultural Control
Houndstongue might be managed temporarily with herbicides or, in the future, with insects, but long-term reductions must include planting competitive plant species to occupy bare ground once infested by the weed. Many improved grass species can be seeded in late fall or winter when seedbeds are properly prepared. An initial herbicide treatment is important to suppress problem perennial weeds before seeding.
Important grass characteristics to be considered for long-term control of problem weeds include 1) adaptation to the soil and climate, 2) ease of establishment and 3) competitiveness with weeds.