Weeds

Weeds – plants that interfere with management objectives – pose a significant challenge to management of rangeland ecosystems, especially those with multiple-use objectives. Rangeland weed problems vary from poisonous native plants causing direct livestock losses to non-native invasive weeds that negatively impact forage quantity and quality, reduce species diversity and alter the way ecosystems function. Effective management of rangeland weeds requires a systems-based approach, where grazing management, weed control techniques and rangeland monitoring all work together.

If left unmanaged for even several years, invasive weeds are capable of expanding rapidly, with exponential increase in the negative impacts (such as reductions in livestock forage, crop production or wildlife habitat) felt by the landowner or manager. The decision to implement a weed management program should be evaluated within the context of the particular situation, whether it is a smaller-acreage property, a ranch agribusiness or a multi-thousand acre federal grazing allotment. There are many different approaches for managing weeds in rangeland ecosystem, and each one depends upon the biology of the target weed, its distribution and severity of impacts and the desired goals for the management area being affected. Below are a few important concepts when managing weeds in rangelands.

Early Detection-Rapid Response

Many examples illustrate how locating and controlling an invasive weed population in the early stages of invasion is less costly, with a higher rate of success. It is easier and cheaper to hand-pull three individual spotted knapweed plants than it is to manage a 250 acre knapweed patch. Weeds can change the way the system functions, potentially leaving a legacy of altered biotic and abiotic conditions even after the weeds are gone. The longer a weed impacts a site, the more likely it is to leave a legacy. Early Detection-Rapid Response (EDRR) is a weed management strategy that emphasizes searching for small, newly-started populations of weeds that may be new to an area and taking management actions before the weeds become very well established. Wyoming citizens can help identify and report weed infestations while driving, riding or hiking throughout their favorite places by several different methods: calling your local weed and pest or extension office, or via a smart-phone application specifically designed for reporting invasive weed populations (www.eddmaps.org).

Integrated Weed Management

There are many weed control methods, with control being defined as a means of causing damage to the target weed which reduces its ability to reproduce, spread and compete for resources against desirable plants, or, in other words, actions that harm or kill weeds.  The most often used control methods are physical, biological, cultural and chemical control. Although each of these control options has its own unique positive and negative aspects, a weed management program that integrates multiple control methods may achieve the best long-term results. An integrated weed management (IWM) approach uses multiple methods of control within a larger management strategy. For example, incorporating targeted grazing (biological) and herbicides (chemical) to manage leafy spurge populations with long-term monitoring of infestation characteristics (cultural) is an integrated weed management approach with a high probability of success if matched to the invasion site.