What does it mean when I see ester or amine in the active ingredient of an herbicide?

Question What does it mean when I see ester or amine in the active ingredient of an herbicide?

Answer Most people don't want to understand how things work. They simply want the name of a product that will do the job. Knowing the active ingredient in an herbicide is an important thing.

Reactions to herbicides are different between grasses (ex. 2,4-D may harm centipede and not harm fescue). Reactions to herbicides are also different between weeds.

Winter weeds, like wild garlic, henbit or chickweed, can be tough to control because they may go in and out of dormancy throughout the winter. As the weather bounces back and forth from warm to cold, weeds will grow during the warm days and rest on the cold days. Weeds are hardest to kill when they are resting.

Winter air is also drier than summer air. Since the humidity is lower, winter weeds have developed growth characteristics to protect their leaves from drying out. Characteristics like waxy, fuzzy or small leaves protect the weeds from the harsher winter weather. These plants also tend to grow flatter to the ground in order to preserve heat and moisture. These growth habits and patterns make it more difficult to control winter weeds with herbicides.

Some herbicide molecules may not be readily absorbed into a winter weed, because it's not able to effectively penetrate the waxy covering of a leaf. Altering the parent molecules may increase the ability of the herbicide to penetrate through the leaf more effectively. For some postemergent herbicides, formulating the molecules as an ester or salt is frequently done to facilitate absorption through the leaf.

Some herbicides come in amine and ester formulations. Amine formulations are less volatile (likely to vaporize and drift) than ester formulations. As ester compounds generally have a higher volatility, they may damage non-target plants during the summer months. Esters are best used during the late fall, winter, or very early spring (before buds break) when temperatures are cool. Esters used at this time are more effective than amines, as they are more readily absorbed by plant tissue.

The name of the pesticide will sometimes give you a clue. For example, Coolpower is the name of a broadleaf herbicide that can safely be used on centipede during the winter.

When talking about warm season grasses, another factor to consider during the winter is the dormancy of the grass. Sometimes the weather warms up enough to cause some of the grass to break dormancy (or delay dormancy). Herbicide applications during warm winters may produce a variation of results from a case of the yellers to dead spots. For the out-of-state folks, yellers is another way of saying "yellow coloration of the turf".

Read the label of every pesticide that you use. Apply the correct rate whether it is an ester, amine or some other formulation. If you want to know more about pesticides, then call me at 910-893-7533, write me at PO Box 1089, Lillington, NC 27546 or email me at gary_pierce@ncsu.edu More info can be found on the web at http://www.ces.ncsu.edu/depts/hort/consumer/hortinternet/pesticides.html