Weed Control

Importance of Weed Control

The efficient and economical management of weeds is a major factor in the production of all crops, cultivated, as well as rangeland. Noxious weeds are an economic and environmental problem requiring intensive long-term management. Education and cooperation, rather than enforcement, are and will be the key to the success of the weed management program. The objective of the Weed Board will be to control, contain, and in some cases, eradicate noxious weeds and to maintain a vigilance for new and potential invasions of noxious weeds into the county.

This program is supported by a tax levied throughout Butte-Silver Bow.

The control of noxious weeds in Butte-Silver Bow is of utmost importance. Please read the information provided below to identify weeds and learn more.

Biological Weed Control

Biological weed control is an evolving science. Researchers are working to understand how plant-insect and plant-disease interactions and interrelationships influence weeds, biological control agents, and the environment. It is important to know how these processes can be manipulated to benefit one organism (the biological control agent) over another (the target weed).

Invasive Weeds

Many introduced weeds in the United States are not problems in their native lands but are merely members of their respective plant communities. Biological control seeks to use some of the native land's biotic factors that suppress the populations of plants such as leafy spurge, spotted and diffuse knapweed, tansy ragwort, and purple loosestrife (as well as hydrilla, water-lettuce, water-milfoil, and water-hyacinth).


Continued research in the field of biological control is needed to learn how a plant's natural enemies survive, the plant's response to natural enemies, how each is influenced by conditions and forces in the environment, and interrelationships between natural enemies and hosts. Integration of effective biological control agents into weed management programs is the ultimate goal of a weed biological control program.

Integrated Weed Control

Integrated weed control has been talked about for years. Only recently has it become common to combine mechanical, chemical and biological controls to combat invasive weeds. These tactics can be combined successfully. However, there are limitations to integrating these methods. It just takes a little understanding of the weed, the insect, and the best times to spray.

Herbicide application usually does not kill the bio-control insects outright. However, if one's herbicide application burns off the top of the weed, if the quality of the weed significantly declines, the insect will either have to move to unsprayed plants or perish.

Integrating Herbicides With Insect

The best information on integrating herbicides with insects has come from scientific studies. On a case by case basis we have learned which insects and herbicides can be used together. Studies have shown that integrating herbicides with weed-feeding insects can enhance weed control in certain cases. In most situations, the timing of herbicide applications can be adjusted so not to disrupt the mating / egg laying / feeding of the insect. Frequently, fall applications have proven to be the least disruptive to the life history of the beneficial insect.