Grayson County Master Gardeners - The evils of the garden: fire ants

By: Abby Powell Email
By: Abby Powell Email

Fire ants are a variety of stinging ants with over 280 species worldwide. The fire ant that has taken over all of the southern states is Solenopsis Invicta, which arrived in Mobile Alabama in 1930 on a freighter from South America.

Genus: Solenopsis
Species: Invicta

Well over five billion dollars a year is spent trying to combat fire ants in the USA. About half of the US population in southern states gets bit by fire ants each year.

A typical fire ant colony produces large mounds in open areas, and feeds mostly on young plants, seeds, and sometimes crickets. Fire ants often attack small animals and can kill them. Unlike many other ants, which bite and then spray acid on the wound, fire ants bite only to get a grip and then sting (from the abdomen) and inject a toxic alkaloid venom called solenopsin. For humans, this is a painful sting, a sensation similar to what one feels when burned by fire—hence the name fire ant—and the after effects of the sting can be deadly to sensitive individuals. The venom is both insecticidal and antibiotic.
First aid for fire ant bites includes external treatments and oral medicines.
• External treatments: a topical steroid cream (hydrocortisone), or one containing aloe vera. Also, regular toothpaste can be a quick and simple relief. A simple solution of half bleach and half water applied immediately to the area can reduce the pain, itching and, perhaps, pustule formation.[8]
• Oral medicines: antihistamines.
Victims who experience severe or life threatening allergic reactions to fire ant insect stings should visit a doctor or hospital immediately upon contact as these reactions can result in death. These more severe reactions include severe chest pain, nausea, severe sweating, loss of breath, serious swelling, or slurred speech.[9]
Fire ants nest in the soil, often near moist areas, such as river banks, pond edges, watered lawns and highway edges. Usually the nest will not be visible as it will be built under objects such as timber, logs, rocks, pavers, bricks, etc. If there is no cover for nesting, dome-shaped mounds will be constructed, but this is usually only found in open spaces such as fields, parks and lawns. These mounds can reach heights of 40 cm (15.7 in). The mounds that the fire ants live in can also be as deep as five feet.

Fire ants are not picky eaters. They are omnivores and will eat almost any plant or animal material, including other insects, ground-nesting animals, mice, turtles, snakes, and other vertebrates, young trees, seedlings, plant bulbs, saplings, fruit and grass. When foraging for food, the oldest and most expendable 20% or so of the colony’s workers explore within 50 - 100 feet of the nest in a looping pattern.
Even though worker fire ants can chew and cut with the mandibles, they can only swallow liquids. When they encounter liquid food in the field, they swallow it to one of their two stomachs. One stomach saves food to share with the colony and the other one is to digest food for themselves. Solid food is cut to carrying size and brought back to the colony for "processing." Fireants prefer protein foods (that is, insects and meats) but will feed on almost anything and everything.
Colonies are founded by small groups of queens or single queens. Even if only one queen survives, within a month or so the colony can expand to thousands of individuals. Some colonies may be polygynous (having multiple queens per nest). Large colonies may have up to a half million ants.

A queen is generally the largest individual in the colony. The primary function of the queen is reproduction; she may live for 6-7 years and produce up to 1,500 eggs per day. Many fire ant colonies will have more than one queen.

An established nest can have up to 8 inactive sub-queens that will flee the nest if threatened, which is why poisoning a nest may not completely rid a property of the ants.

Male drones mate with the queen for the sole purpose of producing offspring. Their lifespan is approximately three days.

The workers are sterile females who build and repair the nest, care for the young, defend the nest, and feed both young and adult ants. The worker ants also go find supplies to build up the colony.

Fire ants will cause actual damage to your garden, and you should do your best to get rid of them. They're harmful in a lot of ways. First off, as you experienced, they will bite you whenever you try to tend to it or harvest any vegetables you plant out there. Second, fire ants will damage many kinds of plants that can be food for them. They will often eat the buds of plants or tunnel through the roots of others. They will eat seeds or pods or anything with nutrition. Third, fire ants use aphids for food, and will protect them from predators and actually cultivate them. Aphids can cause serious damage to plants, even if the ants themselves don't.

The big problem, though, is that many insecticides and baits cannot be used in gardens. You need to read the instructions carefully before trying to use them there - especially if you are going to eat something coming out of it. Some baits can't be used in gardens themselves, but can be sprinkled just outside it. Some, like Green Light, are safe to use there.

There are also some natural remedies that, while not foolproof, might be your best bet with a garden. First of all, put out baits in any other parts of your yard where you find nests. It doesn't really help to just get rid of them in one place, because they'll start another colony there all over again.

The Two Step is a proven method of reducing imported fire ant populations in heavily infested home lawns and ornamental turf. Briefly, it is the: 1) once or twice per year broadcast application of a bait product, and waiting several days to a week before; 2) treating nuisance mounds using an individual mound treatment such as a dust, granule, bait or drench insecticide. Otherwise, wait for the bait treatment to take effect. This method reduces the over-reliance on use of individual mound treatments and is suitable for treating larger areas.

Broadcast Baits for Fire Ant Control
These products are designed for the homeowner and are widely available in retail stores, garden centers and farm and ranch supply stores (Wal-Mart, Lowe’s, Home Depot, CoOp, Tractor Supply, etc.). They are sold in small containers with enough material to cover a home yard up to a few acres. For areas larger than about 10 acres, it is usually much more economical to purchase a professional or agricultural product in 25 lb. bags.
• Amdro
• Amdro Fire Strike
• Amdro Yard Treatment
• Amdro Ant Block
• Conserve-containing products (Green Light, Payback, etc.)
• Over ‘n Out
• Spectracide Once and Done

The Texas two-step approach to get rid of fire
The currently best proven approach to effectively manage fire ants, is called the Two-Step Method. This approach works best in fully infested areas (five or more mounds for each quarter-acre of yard) or where there is little or no concern for preserving native ant species.
Two-stepping includes broadcasting a bait insecticide over your entire yard sometime between late August and mid-October, and then treating individual, problem mounds with an approved mound drench, granule, bait, or dust insecticide.

Step One: Baits
Fire ant baits consist of pesticides on processed corn grits coated with soybean oil. Worker ants take the bait back to the colony, where it is shared with the queen, which then either dies or becomes infertile. Baits currently available include Amdro, Siege, Logic, Award, Ascend, or Raid Fire Ant Killer. Baits are slow-acting and require weeks to months to achieve 80% to 90% control. Bait products can be used to easily treat large areas effectively. They contain extremely low amounts of toxins. For best results:
• Use fresh bait, preferably from an unopened container.
• Apply when the ground and grass are dry and no rain is expected for the next 24 to 48 hours.
• Apply when worker ants are actively looking for food, usually in late afternoon or in the evening. To test, put a small pile of bait next to a mound and see if the ants have found it within 30 minutes.
• Apply baits with hand-held seed spreaders. Don't apply baits mixed with fertilizer or seed.
• Baits can be applied anytime during the warm season. When applied in late summer/early fall, ants are still foraging and it's easier to predict weather patterns. Then the bait can take effect over the winter while you're indoors. Re-apply baits once or twice a year. (see Tackle Fire Ants in the Fall).
Step Two: Individual Mound Treatments
Chemical. With dust products, no water is needed and they act fast. However, they leave a surface residue. Liquid drenches generally eliminate mounds within a few hours and leave little surface residue after application. Granular products are relatively fast acting and usually require putting granules on and around the mound and then sprinkling 1 to 2 gallons of water on without disturbing the mound. Closely follow directions on the label.
Organic. Pouring 2 to 3 gallons of very hot or boiling water on the mound will kill ants about 60% of the time. Otherwise, the ants will probably just move to another location. Very hot or boiling water will kill the grass or surrounding vegetation that it is poured upon. Other natural or organic methods include mound drench products containing plant derived ingredients (e.g. botanical insecticides) and biological control agents.

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