|Fire ant carrying bait back to the nest. Baits do not have to be|
applied directly to a garden to control fire ants living inside a
vegetable garden. USDA image courtesy Bugwood.
A standard, low-risk treatment on commercial, residential and school properties is use of a fire ant bait; however many of the most commonly used baits do not allow direct use in vegetable gardens. Fortunately, there is a work-around.
In most cases the simplest way to get fire ants out of a small- to medium-sized garden is to apply a fast acting fire ant bait around the outside garden perimeter. This should be a legal application for all fire ant baits (check your label to be sure), and since fire ants do not pay much attention to garden edges, the garden infesting ants will readily pick up bait from the surrounding ground. Yes the bait does end up inside the garden anyway, but only inside the fire ant nests, where there is no risk of it contaminating leafy vegetables.
For larger gardens or cropland where perimeter treatments might be less effective, several fire ant baits are legal for use. Spinosad and abamectin-containing baits generally allow garden application (e.g., Clinch®, Fertilome® Come and Get It, and Payback®). In addition, Extinguish® (but not Extinguish® Plus) fire ant bait containing methoprene has a label that allows use on cropland. However Extinguish is too slow for most gardeners, requiring approximately two months for maximum control.
In addition to baits, mounds can be treated directly with any of several mound drenches labeled for use in gardens. The eXtension website contains recommendations for a two-step (bait and mound treatment) approach to fire ant control in both conventional and organic vegetable gardens.
Appreciation to Dr. Paul Nester (Texas A&M AgriLife) for supplying some of the information used in this post.