The Deer Steward’s Guide to Herbicide Terms

June 24, 2016 By: Brian Grossman

Herbicides can play a key role in your deer habitat management strategy. Their use can assist with creating and maintaining viable food plots, help control non-native, invasive species, and even control less-desirable brush and trees in your woodlands. But using herbicides can be intimidating. There are hundreds if not thousands of formulations on the market, and each has its own unique requirements for safe and effective use. Despite such a wide variety of herbicide options, deciding which one best suits your needs doesn’t have to be complicated. With an understanding of some of the most common terms used to describe and classify herbicides, you’ll be able to narrow down your choices and pick a herbicide that meets your habitat project’s needs and requirements. Let’s take a look at some of those key terms.

Active Ingredient – The active ingredient of an herbicide is the component responsible for its ability to control target plants. In the case of the popular herbicide Roundup, the active ingredient is glyphosate. Why is this important to know? Because often there are multiple manufacturers producing herbicides with the same active ingredient but marketed under different trade names. So to avoid confusion when shopping for or discussing your herbicide needs, it is often best to refer to an herbicide by the active ingredient rather than a trade name.

Trade Name – As mentioned above, an herbicide “trade name” is the name the manufacturer gives its product. For example, glyphosate is marketed under scores of different trade names, including Roundup, Ranger Pro, Honcho, Glypro and Touchdown, to name a few

Mode of Action – The mode of action is the method by which an herbicide controls targeted plants. It typically describes the biological process or enzyme in the plant that the herbicide interrupts, affecting the plant’s growth and development. Knowing the mode of action is important in selecting the right herbicide for your specific application, as well as avoiding overuse of herbicides with the same mode of action, which can lead to herbicide resistance.

Pre-emergence Herbicides – Pre-emergence herbicides are those applied before the target weeds germinate and emerge. Certain pre-emergence herbicide products require mechanical incorporation prior to planting, while others may be applied during or after planting. Most pre-emergence herbicides have little activity on existing vegetation and can remain active in the soil from a few weeks to well over a year, depending on the application.

Post-emergence Herbicides – As the name implies, post-emergence herbicides are applied to the foliage of the target plants after they have emerged from the soil and while they are actively growing. Glyphosate would be an example of a commonly used post-emergence herbicide.

Contact Herbicides – Contact herbicides only kill the portion of a plant the herbicide comes in contact with. They are often fast-acting, with results in as little as a day, but they don’t kill down to the root of the plant, so resprouting is likely. Contact herbicides are not typically used in food plots or other habitat management scenarios.

Systemic Herbicides – In contrast to contact herbicides, systemic herbicides are absorbed by the plant and carried to the root system, killing the whole plant. While they don’t typically work as quickly as contact herbicides, they produce better long-term results.

Selective Herbicides – Selective herbicides kill certain types of plants but not others. For example, the herbicide clethodim kills grasses but does not harm broadleaf plants. The herbicide 2,4-D does just the opposite, killing broadleaf weeds but leaving grasses unscathed.

Non-selective Herbicides – Unlike selective herbicides, non-selective (or broad spectrum) herbicides kill (or damage) all plants. These are commonly used to kill all existing vegetation in a field prior to planting a food plot. Glyphosate is the most common non-selective herbicide used in food plot management.

Residual Effect – Some herbicides remain in the soil and continue to be active for several days, weeks, or even months after application. While this residual effect can be good for controlling weeds in a food plot, it may limit your options for crop rotation, depending on the length of time the herbicide remains active in the soil. For example, if you used the pre-emergence herbicide imazethapyr, you should not plant oats, grain sorghum, or sunflowers at that site for 18 months after application. Always check the herbicide label for recropping restrictions.

Adjuvants – An adjuvant is any compound that is added to a herbicide or tank mix to improve the mixing, application, or effectiveness of the herbicide. For most deer stewards, adjuvants will come in the form of non-ionic surfactants and crop oils. Both aid the herbicide in “sticking” to the plants on which they are sprayed. Some herbicides – specifically some of the glyphosate products – come with an adjuvant already incorporated into the herbicide. Others call for an adjuvant to be added to the tank mix before spraying. Always read your herbicide label for any recommended adjuvants.

The key to any successful herbicide application is understanding your needs in an herbicide and matching those needs to the best available product. Knowing the key terms discussed above should help you in that regard and give you a better idea of how the herbicide works and what expectations you should have for its effectiveness and longevity.

Always carefully read the label of any herbicide you are using and follow all safety and usage instructions.

About Brian Grossman:

Brian Grossman joined the NDA staff in August, 2015 as its Communications Manager. Brian is responsible for amplifying NDA’s educational message for hunters through social media, e-mail, the NDA website, and Quality Whitetails magazine. He has been a freelance writer, photographer, videographer and web designer since 2003. A trained wildlife biologist, Brian founded the Poor Boys Outdoors and Working Class Hunter web shows and associated media during his free time while working full time as a wildlife manager. He came to NDA from the Georgia DNR Wildlife Resources Division, where he was a field operations supervisor, overseeing management of 15 Wildlife Management Areas. Brian currently lives in Thomaston, Georgia with his wife, Tina, and his two children, Dakota and Brooke.

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