Introduction to herbicide terminology for wildlife habitat managers

Buckets sit on the back of a truck.

Example herbicides. Photo by Luke Stamper, LSU AgCenter.

Herbicides are one of many tools available to wildlife habitat managers. When used in accordance with label instructions, they can prevent or control woody encroachment in moist soil impoundments, eliminate competing vegetation from supplemental food plots, limit spread of non-native invasive species like Chinese tallow, and remove less desirable trees from woodlots, among many others. Given the large number of options on the market, choosing the right herbicide can be difficult. Below we’ve defined common terms used to describe herbicides so that you can select a product that will help you meet your management goals.

Trade name — Trade name is the brand or trademark by which a commercial product is identified. The same active ingredients can be found under a multitude of trade names. The most used example is glyphosate with tradenames such as Cornerstone, Roundup and Accord that all contain the same active ingredient.

Active ingredient — The active ingredient is the chemical formulation responsible for phytotoxicity and control of targeted weed species. Active ingredients are important to understand because of the many trade names an active ingredient is marketed by. When you know the active ingredient you are searching for, you can better understand the herbicide label and ensure you are purchasing the correct product.

Mode of action — In general, the mode of action (MOA) is the way an herbicide controls a group of weed species through the interruption of key plant functions. Examples of MOAs are growth regulators, photosynthetic inhibitors, amino acid synthesis inhibitors and many others.

Pre-emergent/Pre-emergence herbicide — According to the Weed Science Society of America, pre-emergence describes herbicides that are applied to the soil before the emergence of the intended weed or crop. This herbicide application method can control weeds before or soon after they emerge.

Residual herbicide — Any herbicide that remains active in the soil for some period (days, weeks, months) that cause injury or death to emerging weeds. Soil-applied pre-emergent herbicides are an example of herbicides that have residual activity because they can control emerging weeds for several days or weeks giving the intended crop time to become established.

Post-emergent/Post-emergence herbicide — A herbicide that is applied post or after the target weed has emerged. This type of application can control already established weeds unlike the majority of pre-emergent herbicides which have little activity on established weeds.

Systemic herbicide — When the herbicide is applied and is translocated throughout the plant causing injury or death. University of California Weed Science illustrated this by writing that systemic pre-emergent herbicides can be taken up by the roots and moved to leaves while post-emergent herbicides can be taken up by the leaves and moved to the roots.

Contact Herbicides – Unlike systemic herbicides, contact herbicides only affect plant tissue that is directly applied with herbicide and does not have the ability to move to untreated plant parts.

Adjuvant — An adjuvant is any substance that already exists in a herbicide formulation or that is added to the tank in which it modifies the herbicidal activity or the characteristics of the application.

Herbicides are just a small component in the toolbox of habitat management but absolutely have a place here in the Deep South where weed seed banks are prolific and often problematic. Gaining some understanding of the terminology used to describe these products can increase your success along the way. Good luck this growing season!

Luke Stamper is a wildlife and forestry extension agent in northeast Louisiana.

6/1/2023 2:23:44 PM
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