Most successful weed management plans use a number of methods: herbicides, mechanical, cultural, and when appropriate biological control. Use of multiple methods at the same time is called Integrated Pest Management - or IPM.
Biological control of weeds is the use of one organism to control another. Classical biological control is the introduction of control agents - usually insects - into a region that is not part of their natural range, to permanently reduce the populations of selected weeds. They are used to REDUCE, not GET RID OF the weeds.
BIOLOGICAL CONTROL MAY BE AN OPTION FOR YOUR WEED PROBLEM IF.....
You don't expect the weed to be totally eradicated
You don't need instant gratification
You are willing to check release sites for establishment and impact
You are willing to give the agents the time they need to work (2-5+ years) before resorting to other weed management options (spray, mechanical,cultural)
Knapweed Agents - Thirteen insects have been released that will attack knapweed species. Some prefer other knapweed species over spotted. The most effective established agents prefering spotted knapweed are A.zoegana, C. achates, Larinus spp., and Urophora spp. Work in Canada shows the best control if seedhead feeders and root feeders are combined.
Flower feeding beetles (Brachypterolus pulicarius) are likely already in your yellow toadflax. A stem-boring weevil (Mecinus janthinus) that attacks Dalmatian toadflax is showing promise.
Beetles (Aphthona spp.) that eat the leaves and seed have been the most visible and effective so far. Grazing by sheep, goats, llamas or hogs is an effective way to keep the plants from blooming.
Local Programs: Contact your State Department of Agriculture, County Noxious Weed Office, Local Cooperative Weed Management Area (CWMA) or Extension Agent.
USING LIVESTOCK FOR WEED MANAGEMENT
Prescription grazing - is carefully controlled grazing to meet land management objectives. It can reduce weeds in crop systems, control weeds in tree crops, remove weeds in sensitive areas, and control weeds on range lands.
KEYS TO PRESCRIPTION GRAZING -Timing of grazing - when weeds are most susceptible and taste the best to the animal, generally early spring in North Idaho. -Frequency of grazing - Depends on the weed species; life span, reproduction, longevity of seeds in the soil, and how it reacts to grazing. -Stocking rate - How many animals do you need on how much acreage? It depends on the density of the weed infestation, the palatability of the weed, and your specific goals.
Pick the right animal for the job - Pick the correct species and breed for your weed. It is a myth that any old goat (or sheep, or cow) will do.