You know your property better than anyone, so make your own weed management plan.

Natives and desirables are not nearly as competitive as weeds–weeds will quickly fill any empty niche left by herbicides.  Spot spraying will work better overall, and in the long run, since broadcast spraying also kills desirable plants.  You may get rid of one weed temporarily, but another one just as noxious will most likely take over that empty niche.  A way to avoid this is to immediately seed with a native.  Since natives tend to be slower to establish, planting a quick growing annual along with native seeds can fill that niche until the natives can establish.  Success in suppressing weed regrowth may be accomplished by planting an annual grain crop (barley is a good option) along with native seeds.  The deer and elk will browse the barley heads while pressing the seeds into the earth with their hooves (along with the added perk of fertilizing in the process).

Biocontrol insects are well established in the Bridger Canyon area.  Leafy spurge, knapweed, Canada thistle, St. Johnswort, toadflax, and common mullein all have insect populations present. (Please note that houndstongue agents are prohibited from being moved or marketed, but these insects have already migrated from their release sites in Canada as far south as Colorado.) Our climate can be quite challenging, so some years the insects may only survive and not flourish. Adding to these populations is usually not economically feasible.  Once established, the insects will move to new weed infestations on their own. 

Having an understanding of how biocontrol works will help with expectations:

• Weed-feeding insects do not eradicate weeds.  In the weeds’ original habitats (Europe and Asia) the insects have evolved along with the weeds to keep them in check–the weeds are then simply well-behaved members of the plant community.
• Biocontrol insects cannot prevent weeds–they need food, so they can only move to new infestations.
• Beneficial insects are self-perpetuating–there is no need to put new populations out year.  These agents may not always be visible, but they are very hardy.
• Biocontrol agents may be collected and moved around, but they will spread out on their own.  The insects follow their food source.
• Biocontrol agents will not spread to crops or gardens–they are host-specific to their target weed.

The Field Guide for Biological Control of Weeds in the Northwest is an excellent resource for identifying weeds and their specific beneficial insects, determining biocontrol establishment, and understanding modes of attack and life cycles.

Thanks to Cyndi Crayton for putting this article together. Also check out our Weeds page.