Fire Ants in the Garden

As the weather cools off and people get back in their yards and gardens the red imported fire ant (Solenopsis invicta) becomes enemy number one.  The non-native, red imported fire ant (RIFA) can have large colonies with 80,000 to 240,000 workers.  Fire ants have both single and multi-queen fire ant colonies.  Multi-queen colonies are not aggressive towards each other which means you can have more mounds on one property.  Both single and multi-queen fire ant queens live between two and six years.  A one-year old colony can begin to produce reproductive ants.  These ants have wings and fly or swarm during the day usually after a rain.  These queens form new colonies after mating occurs.

Identification

Fire ants usually build visible mounds that they will defend if disturbed.  Fire ants can bite and sting, often creating a pustule at the site of the sting.  Interestingly, the venom from the sting has necrotoxic properties.  Red imported fire ant workers are polymorphic, meaning they have different size workers.  If the ants in the mound are all the same size, then there is a good chance that it is not a fire ant mound.  The native fire ant (Solenopsis geminata) has workers who’s heads are more square-shaped and disproportionate to its body size as compared to a red imported fire ant.

Control

If your property is covered in fire ants then a broadcast application may be the best solution.  However, finding and treating individual mounds is also an option.  Finding each individual mound is the disadvantage to treating them separately.  The disadvantage to treating large areas is that the ants may not discover the bait for an extended period of time.  The bait may also become inactive by the time that it is found.  However, the easiest method for control for homeowners is to use a bait and most treat just the individual mound.  The trick is to not put the bait on top of the mound unless the label says otherwise.  Generally, ant baits are meant to be lightly scattered near the mound where the ants are foraging.  Baits are slower acting because they have to be taken back to the colony and then fed to the queen, thus disrupting the life cycle.  This can however, take some time.

Selecting Products

Gardeners want to control fire ants in their vegetable gardens because they feed on crops and are a nuisance.  Not all products are labeled for areas where food is grown making product selection tricky.  Spinosad is one of the few baits that is labeled for vegetable gardens, is also OMRI or organic certified, and available to homeowners.  It is important to always check the label and make sure that the site is on the label, especially if it is for a treating ants in a fire ant mound.  Since many products are not labeled for vegetable gardens, consider treating the mounds outside of the garden area with those labelled for lawns or ornamental plants.  This will help reduce the pressure of ants moving into the garden area.

 

Some examples of products that are currently labeled for vegetable gardens include, but not limited to:

 

Baits
  • Spinosad (Fertilome Come and Get It) OMRI certified, approved for organic gardens
  • S-methoprene (Extinguish Professional Fire ant Bait)
  • Pyriproxifen (Esteem Ant Bait)
Organic Options
  • D-limonene (Orange Avenger) OMRI certified, approved for organic gardens
  • Spinosad (Greenlight Lawn and Garden Spray, Fertilome products, Moterey Garden Insect Spray, several Bonide products) OMRI certified, approved for organic          gardens
  • Diatomaceous Earth (DE) (usually moves the colony, but does not eliminate them)

 

Examples of products NOT currently labeled for vegetable gardens, but can be used in surrounding areas include:

 

  • B-cyfluthrin (Ortho Bug B Gone Max, Ortho Max Lawn adn Garden Insect Killer for Lawns, Over N Out, Bayer Lawn and Garden)
  • Acephate (Ortho Orthene Fire Ant Killer, Surrender Fire Ant Killer, various others)

 

Always read the label of any pesticide product to make sure it is labeled for your state and the site. For example the label should state “vegetable gardens or fruit crops” if that is where you intend to use it.  Always follow label directions.

 

 

 

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