Understanding a Pesticide Label- Herbicide Groups

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Herbicides work in different ways in weeds to ultimately control their growth. They are separated by their Mode of Action (MOA) due to how they control a plant. For example, Roundup is a trade name for a herbicide called glyphosate. It is a Group 9 herbicide which is an Aromatic Amino Acid Synthesis Inhibitor. This chemical works by inhibiting a protein that’s essential for growth. It is important to know how herbicides are grouped and why in order to properly rotate their use to prevent resistance to a specific herbicide that may come from repeated use. Some Mode of Action groups contain herbicides with different chemicals that control plants in similar ways. For example, 2,4-D and Dicamba are both group 4 herbicides, Group 4 herbicides are Growth Regulators that cause uncontrolled cell growth in the plant like twisted leaves and stems. This happens by the herbicide changing the hormones of the plant to alter its growth. 2,4-D uses Phenoxy-carboxylic acid while Dicamba uses Benzoic acid. All three of the chemicals in this article are commonly used and can be safely applied by homeowners if they read and follow the pesticide label. Before making an herbicide application it is important to know what you are trying to control and what herbicides control the specific weed you are trying to address, as some weeds are resistant to certain herbicide groups. Knowing what weed you’re trying to control is half the battle and can certainly save you time, money, while helping be a better environmental steward.

For more information call North Carolina Cooperative Extension- Lee Center at 919-775-5624.