Ferguson: Fall is a good time to apply bait for fire ant management

Published 3:13 pm Friday, October 29, 2021

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In yards where fire ants are a problem, one to three broadcast applications of bait per year is a cost-efficient foundation for a management program.

Baits contain small amounts of insecticide mixed with materials that attract ants. If used correctly, worker ants bring the bait back to their mounds so that other ants in the colony are exposed to the insecticide. Because ants themselves distribute it, using bait effectively doesn’t require knowing where all mounds are or physically getting an insecticide to all parts of a colony. Fire ant mounds can extend quite deep in the soil where they aren’t restricted by a high water table.

For baits to work well, ants need to think of them as food. They should be used when fresh and applied when the ground is dry, with rain not expected within the next 24 hours.

The temperature at the time of application is important. Fire ants do not seek out food as actively when temperatures are hotter than 90 degrees Fahrenheit or cooler than 65 to 70 degrees Fahrenheit. For this reason, application in fall and spring is often recommended. If you apply bait during the middle of the summer, do it at a time of day when temperatures are cooler.

To make sure that fire ants are active enough for treatment to be effective, you can put a potato chip, a piece of hot dog, or a piece of the bait itself near a mound and check to see if ants are present within about thirty minutes. Do not disturb mounds themselves before putting out bait.

There is a wide range with respect to how quickly baits work. Ones with indoxacarb and metaflumizone work quickly, killing most ants within about one to two weeks. On the other end of the spectrum are products with insect growth regulators like methoprene and pyriproxyfen. It can take several months for these to have their maximum effect. Products with ingredients like hydromethylnon and spinosad fall in the middle.

Pay attention to the rate at which the label says to use baits. Rates are typically very low. For example, the application rate for some is only 1.5 pounds per acre, which is equivalent to just 0.55 ounce per 1,000 square feet.

If you want long-term control of fire ants but also need to get rid of them quickly in one or more spots (e.g., where children will be playing), you can take a two-step approach: Apply a bait, wait a few days to give ants time to carry it back into the mound, and then apply a contact insecticide.

Contact insecticides can be in the form of liquids, granular materials that are watered into the mound, or dusts. These work quickly to kill ants that they contact.

When applying a contact insecticide that requires the use of water, it’s important to use enough water to get it down into the mound. Active ingredients in contact insecticides include acephate, carbaryl, d-limonene, spinosad, and various pyrethroids (bifenthrin, beta-cyfluthrin, lambda-cyhalothrin, cypermethrin, deltamethrin, and permethrin).

When using any insecticide, be sure to read and follow label instructions. Not all fire ant products can be used in all situations. Quite a few are labeled for use on lawns. For vegetable gardens or orchards, options are more limited but do exist. Because ants will travel some distance to forage for bait, bait applied outside of but near a vegetable garden or fruit planting can have an effect on ants in the garden, too.

Let me know if you have questions.

Dr. Mary Helen Ferguson is an Associate Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu, 985-839-7855 (Franklinton) or 985-277-1850 (Hammond).