What is Integrated Weed Management?
Weed management is most effective when it integrates a combination of strategies, based on what works best for achieving a particular management goal while maintaining economic and environmental stability. Common methods span a large range and include prevention and cultural, chemical, mechanical, and biological practices.
Integrated weed management (IWM) means integrating multiple methods to manage weeds, using the combination of practices that is most effective for solving the specific weed issue at hand.
These weed management techniques form a “toolbox” in which each “tool” can be integrated into a weed management plan catered to the particular farm and problem. The toolbox includes chemical (herbicide), mechanical, cultural, biological practices, and prevention of weed introduction and spread.
IWM tactics span a wide range of types and complexity. Not all IWM tactics are very complex. Some examples include: equipment cleaning, timely scouting, altering herbicide tank mixes, rotating herbicides, cover cropping, changing tillage practices, and hand-pulling weeds.
Integrated weed management is not an alternative to herbicides in conventional crops. For many decades, herbicides have been the primary means of weed management in conventional crops due to their simplicity, effectiveness, and affordability. IWM is about using all options available to best solve the problem – in many cases in conventional crops, herbicides are part of this solution.
PREVENTION: Monitor inputs to the farm to avoid bringing in things that may be contaminated with weed seeds. To do this, learn how key weeds are spread and whether those weeds are located in areas that the farm is transporting supplies from. Equipment, manure, feed, and crop seed are primary spreaders of weeds. Spread via wind and wildlife is more common for some weed species than others. State-level herbicide resistant weed lists are at weedscience.org.
CHEMICAL: Herbicides are a key part of IWM in conventional and some organic systems. In conventional crops, using multiple effective herbicide modes of action (MOA) is essential for effective control of resistant weeds. This involves combining multiple MOA in tank mixes, and varying MOA between applications and seasons. For MOA with high occurrences of resistant weeds, avoid repeat use in consecutive seasons.
CULTURAL: Cultural tactics are crop management decisions that help the crop be more competitive against weeds and help optimize the effectiveness of herbicide applications. Common examples include timely scouting, row spacing, crop rotation, crop variety selection, timing of planting, and cover cropping. Information about using these tactics for weed management is found throughout this site (Hover on the Weed Management Tools tab, and select Cultural.
MECHANICAL: Common mechanical tools to disrupt weed growth and survival include cultivation, tillage, burning, and hand-weeding. Mechanical IWM tools also include emerging technologies like harvest-time seed destructors, cover crop rollers, and robotic weeders. Mechanical tools should be integrated when appropriate as part of a larger IWM program. Many of these mechanical techniques are available to no-till growers.
BIOLOGICAL: A less common IWM strategy is the use of living organisms, including livestock, insects, nematodes, fungi, and bacteria, to target weeds. Many biological agents target specific weed species, while livestock are relatively more generalist in weed consumption and may avoid eating certain weeds.
For some, IWM is not just another choice for weed control, but rather it is a necessity. Often what drives producers to alter weed control practices is when current strategies are no longer effective, or a new weed enters a field and requires a change in plan. Here are two recent agronomic shifts that are driving change in weed control options:
- The rapid spread of herbicide resistance is limiting the viability of some popular herbicides throughout the US
- Increased consumer demand for organic products motivates some producers to integrate new weed control practices in the absence of herbicides.
What resources are available for learning about IWM strategies?
Numerous resources from around the US are available here on this site – find these under Cultural, Mechanical, Chemical, Biological, Prevention, and Harvest Weed Seed Control. State university extension weed scientists offer training that is catered to the particular state.
For up-to-date recommendations for specific weeds, explore the Weed Info tab on the homepage.
Introductory resources about IWM: