Organic Fire Ant Control
By Kara Masharani
Spring 2006

 

Few sights inspire greater dread amongst gardeners than mounds of fire ants that appear seemingly overnight, setting up residence in the most carefully maintained garden. Ants stream out to feast on organic riches and sting the ankles of any passers-by who dare impede their path. Many an organic gardener has tried a host of rumored remedies to deal with these tiny terrors, from grits to pots of boiling water to borax powder, with limited or no success. Here’s a remedy that’s safe to use around veggies and proven to take care of these little buggers.

 

Oil from the peels of oranges is completely safe for humans but deadly to fire ants – it dissolves their exoskeletons. Recent studies have discovered that orange oil solutions are effective in decimating fire ant colonies and, if the solution reaches the queen, destroying the mound for good. The key here is pouring enough solution to thoroughly soak the mound, and pouring at a time of day when ants are in the mound.

 

An added tip: orange oil solution can also be used indoors to control those fire ants that creep in through the cracks. Lowe’s sells an orange oil spray called Orange Guard, or you can mix up your own. A spray around the base of our back door kills any ants that are trying to creep in and creates a barrier that lasts for 24 hours. That gives me time to get outside and deal with the source of the invasion.

 

Some studies also show that molasses or compost tea used in conjunction with orange oil may enhance the effects. A drop of soap in the orange oil solution helps it to mix with the water. Here’s one recipe for orange oil solution, from Year Round Vegetables, Fruits and Flowers for Metro Houston by Dr. Bob Randall:

 

Orange Oil Recipe for Fire Ants

6 oz. orange oil
1 tbsp blackstrap molasses
a squeeze of liquid dish soap

Add to a gallon jug and fill with water.

 

Drench the mounds when the ants are not out foraging. Fire ants prefer mild temperatures, so in the summers they may be out early in the morning and hiding in their mounds by mid-day, and vice-versa for cold days. A gallon will thoroughly soak one mound.

 

You can purchase bottled orange oil (look for Essential Oil of Orange or D-limonene) and use the above recipe, or pick up a product with orange oil that has its own dilution instructions on the container. Wabash Antique and Feed carries bottled orange oil from Earth and Medina as well as Safer Fire Ant Killer (green bottle with a built-in measuring device) and Concern solution, both containing orange oil. Southwest Fertilizer carries Medina orange oil and the Safer product. Teas Nursery carries Medina orange oil concentrate. I could not find any orange oil products at Home Depot or Houston Garden Centers, but the Lowe’s I visited carried Medina orange oil, the Safer product and Orange Guard spray.

 

Orange oil is definitely the best method to try to take care of your fire ant problem, but there are a few other methods out there you might like to try:

 

The Boiling Water Method

 

Pouring hot water on ant mounds will kill many ants, but it will also kill plants and beneficial critters in the soil. Water should be at least scalding hot, but does not need to be boiling. This works best when you use 3 to 4 gallons of water in each application. This can be problematic because it is difficult to carry such a large amount out to the garden. Studies of this method show it to be only somewhat effective in getting rid of mounds, but on the positive side you will always have the ingredients on hand.

 

The Bucket Method

 

The Bucket Method is an effective but labor-intensive strategy that will get rid of the ant problem, but it may leave you with a few bites, and holes in your garden in the process. Prepare a five-gallon bucket near the fire ant mound with about a gallon of water mixed with orange oil inside it. Then, rapidly dig the mound with a large shovel and dump it into the bucket. Ants that get submerged don’t stand a chance. You can drown any that aren’t already underwater by adding a squirt of dish soap and water from a hose. The soap breaks the surface tension and drowns the ants more quickly. It usually takes overnight to kill the ants. To stay safe, tuck your pants into your socks, wear gloves, and before starting, sprinkle the bucket and shovel with baby powder or cornstarch to prevent the ants from climbing.

 

Spinosad

 

In addition to the use of an orange oil mound drench, Texas A & M recommends applying a spinosad bait while ants are foraging. Spinosad (trade name “Conserve”) is relatively new on the market, and is considered organic as it is produced by a bacteria-like soil organism. It works by disrupting the ant's nervous system. Spinosad is considered nontoxic, although most products containing spinosad recommend use only for ornamental plants.

Fire ant baits containing spinosad are made by Ferti-lome, Ortho, Safer and Green Light. Application of spinosad would be at the opposite time of day than for orange oil; apply it at mid-day in cooler months and in the evening in the summer. Rain or water will dissolve the bait, and the active ingredients will also wear off in the heat and sun, so don’t apply in wet weather.

 

Wabash is one local store that carries the Green Light product and recommends it to organic gardeners. Spinosad bait can also be found at Southwest Fertilizer and Teas Nursery. I could not find it at Home Depot or Houston Garden Center, but I did find it at Lowe’s.