Houndstongue is a controllable problem on range and wild lands

May 28, 2009 By Jane Mangold

(PhysOrg.com) -- Houndstongue--also known as beggar's lice, dog's tongue, sheep bur and woolmat--is not only a general nuisance to those of you who find its sticky seeds stuck in your shoelaces or the hair of your dogs and livestock, but a weed that can impact range and wildlands by displacing native plants and degrading forage quality and capacity for livestock and wildlife.

This biennial weed spends the first year of its life as a rosette of soft, velvety leaves that lack teeth or lobes. During the second year in addition to the leafy rosette, houndstongue produces a flowering stem that may grow one to four feet high. In mid-May to mid-June, flowers will appear that range in color from dull red to burgundy and have five petals that fuse at their base. Each flower develops a cluster of four burr-like nutlets that contain the seed. It's these nutlets that you find stuck to animals and your clothing, and it's these clinging nutlets that help the plant to spread from place to place.

Houndstongue is often found growing along trails, roadsides and even in backyards and flowerbeds. It is often associated with disturbed areas like logging areas and pastures that have been severely overgrazed. Houndstongue is a noxious weed in Montana, Colorado, Nevada, Oregon, Washington and Wyoming and occurs in most U.S. states. Dispersal occurs relatively slowly over time, but colonization of disturbed areas can take place very quickly.

Houndstongue contains pyrrolizidine alkaloids which are toxic to cattle, horses, sheep and goats. Although houndstongue is not very palatable and animals will generally avoid it, livestock may be forced to eat it if confined to a small area lacking in other desirable forage. Livestock may also eat it if it is cut and dried with harvested hay.

Fortunately, houndstongue is relatively easy to control compared to some other noxious weeds. Because houndstongue spreads only by seed and because seed only remains viable for a few years, preventing seed production and spread from year to year is critical. Limiting seed dispersal, finding and pulling new plants early and maintaining competitive desirable plants all go a long way toward houndstongue management.

Small-scale infestations can be readily controlled by removing plants by hand or with a small spade or shovel. A good portion of the taproot must be removed if hand-pulling, or aim to sever the taproot at least two inches below the surface of the soil if digging or grubbing. If you find seeds stuck to your clothing or pets, remove and dispose of them in a garbage bag or burn them in hot fire.

Larger infestations of houndstongue can be managed with herbicides. Rosettes can be controlled using 2,4-D amine. Metsulfuron can be used in rangeland, pastures and disturbed areas and should be applied in mid-June when plants are actively growing. Annual applications may be needed for several years until the seed in the seedbank is no longer viable.

Biological control agents have not been approved for release in the U.S. due to concerns for negative non-target effects on rare native plants that are in the same family as houndstongue. However, there are five insects being investigated as potential agents. One in particular, a root-mining weevil, has been associated with persistent declines in houndstongue populations in British Columbia and Alberta, Canada.

Don't delay in managing houndstongue. While problematic if left untreated over many years, early detection and rapid and appropriate response may allow you to keep this pesky plant at bay.

Provided by Montana State University (news : web)