Farm Progress

Fire ants are back

Jeffrey Stapper

March 17, 2010

5 Min Read

Last year during the drought, our fire ants seemed to have left town, but with all of the moisture recently, they have returned, which brings up numerous questions about best management practices to deal with this pest.

Red and black imported fire ants (Solenopsis invicta and Solenopsis richteri) are invasive species and their painful bites can injure or kill livestock, wildlife, domestic animals and humans. Their large mounds (many as 300 per acre) are unsightly and often damage mowers and other equipment. Fire ants infest buildings and can damage electrical equipment by chewing on wire insulation. The bottom line is: fire ants cost Americans $6 billion a year, including the cost of insecticides.

If you have ant problems, first identify the species. There are hundreds of ant species in the southern United States, including some native fire ant species, and most are considered beneficial insects. Collectively, ants till more earth than earthworms and some prey on other insect pests to help to reduce their numbers.

Fire ants will build mounds almost anywhere—in the open or next to a building, tree, sidewalk or electrical box. A fire ant mound does not have a central opening and when the mound is disturbed, fire ants emerge quickly and begin biting and stinging. Worker fire ants are dark reddish-brown with shiny black abdomens, and are about 1/16 to about 1/4 inch long.

Fire ants can’t be eliminated entirely because it’s not possible to treat all infested areas. The goal of current integrated pest management (IPM) programs is to suppress fire ants as much as possible with biological control methods and use insecticides only where it is economically and environmentally justifiable to do so.

There may not be one “best” method for fire ant control, especially in large areas. Your objective should be to find the method or methods that are most cost-effective and environmentally sound. In areas where these ants do not present problems, doing nothing is certainly one option.

The Two-Step Method can lower cost while reducing environmental damage and improving fire ant control. Step one of this method is to broadcast an insecticide bait once or twice a year, which reduces fire ant colonies by 80 to 90 percent. Step two would be to treat nuisance mounds or colonies that move into the bait-treated areas. Note that Step 2 may not be needed.

This Two-Step Method is likely to be the most cost-effective and environmentally sound approach to treating medium-size to large landscape areas. Certified organic products can be used for broadcast bait and mound treatments. For livestock pastures, select products registered for use on such sites, such as AMDRO PRO, Extinguish, Extinguish Plus, or Esteem.

When using baits, there are some important factors to consider so that the baits work properly. To cover larger areas, use a vehicle-mounted spreader such as the Herd GT-77. Most baits are applied at very low rates, as low as 1 to 2 pounds of product per acre. Calculate the area to be treated and use the smallest spreader setting that allows bait to flow. Apply the bait in swaths, and crisscrossing swaths if needed, until the specified amount is applied. The agitators in some spreaders may cause bait to cake up so that it does not flow properly. Always read and follow the application instructions on the label of the product you are using.

The time of bait application is very important as the ants must be actively foraging for food. Fire ants search for food (forage) at a wide range of temperatures and can be found foraging in almost any season. However, they may be searching for only certain kinds of food, which might not be the oil of a bait. The only reliable way to confirm whether ants are feeding on bait is to offer them a small amount and see if they pick up the particles.

Use fresh bait. The soybean oil in baits becomes rancid over time, making it unattractive to ants. Unfortunately, bait product labels do not list a manufacture or expiration date. Rancid bait smells somewhat like latex paint, unlike the fresh, toasted corn smell of fresh bait.

Because bait can spoil sitting on store shelves, it is important to check its freshness and return it to the seller if it is rancid.

Do not allow baits to come into contact with water. Water ruins baits. In favorable conditions, most bait is picked up overnight or even within a few hours, but for best results, do not apply a bait if rain is expected within 24 hours and do not irrigate the area for at least 24 hours. Avoid application when there is a heavy dew.

With any broadcast bait, you should expect 80 to 95 percent maximum control lasting 3 to 12 months, though the reinvasion rate depends on several factors such as weather and season. No product gives 100 percent control overnight or lasts forever.

It is important to remember that a bait is an insecticide that insects sense to be food. In the case of ants, workers find the bait and carry it back to the colony, where it is fed to the larvae, workers and queens. Foraging workers may consume some of the liquid portion of the bait before returning the particle to the colony.

Most fire ant baits in current use are similar in appearance and odor and in their handling and application. These baits are small, oily, yellowish granules that smell like toasted corn. They consist of three main components, defatted corn cob granules, soybean oil, and the active ingredient which is the actual insecticide that affects the ants.

For more information go to the web site

Any references made to commercial products or trade names are solely for educational purposes with the understanding that no endorsement or discrimination is implied by Texas AgriLife Extension Service or its agents.

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