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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on local landscape and natural history of Pend Oreille County, Washington. A partnership with the Kalispel Tribe of Indians Natural Resources Department has allowed us to expand this program through EPA funding to include more classes, a newsletter and this website.

Managing Weeds

The Toolbox


Weed management decisions hinge on what level of occupancy is acceptable for a particular species. Threatening new invaders are usually on a level of “zero tolerance,” but damage thresholds for established weeds may vary, depending on the situation. Like a golf swing, the most important part of weed management is the follow-through. Without post-management monitoring, the weeds will reoccupy the site to the original damage threshold levels, or may even expand.

Prevention

Prevention is the most cost-effective tool, giving the highest return for the dollar invested. The problem is recognizing the potential for the problems of weed invasion, and then convincing those with the financial resources to invest accordingly. Strategies include education, quarantine, clean equipment procedures and revegetation of disturbed soils.

Cultural

Useful cultural manipulations for weed management include tarping or mulching and planting site-appropriate competitive vegetation. Applying fertilizer on a limited basis can also be an effective cultural technique.

Mechanical

Whether using elbow grease or engine powered machines, mechanical management techniques encompass anything that cuts, mows, pulls, digs or otherwise removes the sprouting stalk from the roots or the roots from the soil. Prescribed burning is listed as a mechanical technique; however the literature to date does not indicate it is useful in controlling wildland weed populations.

Herbicides

The most controversial weed management tool is the use of herbicides. It is often the most cost-effective method, and when applied appropriately, can be environmentally sensitive as well. The herbicide industry has been pushed by the regulations brought about from the public’s concern to develop more specific chemistry that is of lower toxicity and effective when applied at lower rates.

Biological Control

Classical biological control starts with researching insects and diseases of the weed in its homeland. The next step involves testing to make sure they attack only the weed—not native plants or related crops. Only after extensive testing for host specificity – the insect or pathogen must die or fail to reproduce in the absence of its host – will it be cleared for confined release. After more testing to understand its interactions with our environment, it can be cleared for general release. There have been debacles in the past with biocontrol; however, the US Fish & Wildlife Service tightly regulates the process and the risks once associated with this method are greatly reduced.

Biocontrol agents are not intended to eliminate the weed they feed upon. The aim is to suppress the weed’s vigor so they can co-exist with the native plants rather than dominating the scene. For the weeds so widely distributed that there is no hope of completely eliminating them, biocontrol is an elegant addition to the weed control toolbox because it is self-sustaining and self-distributing once established.

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