Control Fire Ants in Pastures, Hayfields and Barnyards

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The days of saying “Alexander County does not have fire ants” are behind us. They are here, as evident by the large mounds you may be seeing along fence lines, pastures, or hayfields and the numerous phone calls our office has received. The sting of the fire ant is painful to both humans and animals. They can also cause damage to equipment in the field or by chewing and damaging wires.

Fire Ant Baits for Pastures and Hayfields

Not all fire ant baits are labeled for pastures and hayfields. Some ingredients cannot be used around grazing animals meant for human consumption. Check the label, before you buy, to make sure the product you are purchasing can be used as you intend.

Currently there are three active ingredients labeled for use as fire ant bait in pastures or hayfields:  Methoprene, Pyriproxyfen, and Hydramethylnon. These products can be found in farm supply stores in small quantities. For larger quantities you may have to special order.

These baits may have haying restrictions so you may have to wait a period of time after application before harvesting hay. Read and follow all label directions.

How much do fire ant bait treatments cost?

If purchasing in larger quantities, such as 25 lb bags, fire ant baits cost around $22 per pound. If you treat at 1.5 lbs per acre you could be looking at $33 per acre to treat. The growth regulator products (Extinguish or Esteem) can be more cost effective as you can skip swaths in application, thereby covering more ground. However these products can take longer to work but seem to work just about as efficiently.

Don’t purchase more bait than you need in one season. There is oil in the fire ant baits and it will go rancid. Fire ants don’t like rancid bait.

How long does it take baits to work, and how long do they last?

Baits are slow acting because the worker ants have to carry the bait back to the mounds to feed the colony. With hydramethylnon (Amdro Pro) you will see results in two to four weeks but it can take two to three months to see the full effects of a growth regulator product.

A single bait application can last a whole season, meaning you will see fewer mounds. You will not get rid of every mound, but if you apply the bait properly and do not get rain for a couple days, you should get around 80% control. However, keep in mind newly mated queens will fly in and establish new colonies. A follow up treatment later in the season may prove beneficial.

When is the best time to apply baits?

Spring is the best time to apply baits. Wait until soil temperatures warm in the spring and the ants are actively foraging. The best way to test the ants to see if they are foraging is to take greasy potato chips or a piece of hot dog and lay near a mound. Check back in 15 to 20 minutes to see if the ants have found them. If the fire ants find the chips or hot dog, they will find the bait!

How do I apply fire ant bait on large acreage?

At most you are only looking to apply 1 to 2 pounds of bait per acre. A typical fertilizer spreader will put our far too much bait. For smaller areas you can use hand seeders designed to spread small seed. For large fields you will most likely want a power-operated spreader. Herd Seeder Company and Spyker Spreaders are two companies that make spreaders designed to spread fire ant bait.

Tips for Using Fire Ant Bait

  • Read the label
  • Use the correct spreader
  • Pick a time when it is not likely to rain for a day or two after treatment
  • Wait until the grass is dry before applying bait
  • Baits are not fast acting but are effective

Quickly Eliminate Problem Mounds in Barnyards

Drenches are a great way to get rid of mounds quickly, especially if they are in a high traffic area like a barnyard. Use a watering can or similar container to mix and apply liquid drenches. Read the label, mix the specified amount of insecticide in water, and pour it over the mound. Avoid disturbing the mound before treating. It is important to use enough liquid to thoroughly soak the entire mound. Depending on the size of the mound, this ranges from one to two gallons. Begin by applying about one-fourth fo the total volume to a 10 to 12 inch band around the outside of the mound. This prevents the queen from escaping through one of the underground foraging tunnels and improves control of workers. Then apply the rest of the drench directly to the mound. Examples of insecticides for use as fire ant mound drenches:  Hi-Yield Garden, Pet, and Livestock Insect Control (permethrin -10%) and Sevin 80 S (carbaryl 80%).

Begin scouting your hayfields and pastures now so that you can develop a treatment plan. If you have additional questions please contact N.C. Cooperative Extension, Alexander County Center at 828-632-4451.