Ants in Vegetable Garden

Dan, I have a raised bed for my vegetable garden that has been invaded by ants due to all of this rain . I'm looking for a way to get them out without using toxic chemicals as this is for my veggies.

- Patrick

Fire ants occasionally feed on vegetable plants in home gardens, but damage is generally minor to negligent, and they typically do not pose a serious threat to vegetable crops. They may, however, tunnel into potatoes underground and feed on okra flower buds and developing pods. The worst damage usually occurs during hot, dry weather.

The primary issue is that fire ants may be a nuisance to gardeners when working in the garden, such as when weeding and harvesting. Their painful bites/stings are the main reason fire ants need to be controlled.

Interestingly, fire ants are effective predatory insects that can help keep down populations of insects that attack and damage our vegetables, such as caterpillars. But they may protect or “tend” other pests, such as aphids, by keeping natural enemies away. In virtually all instances, fire ants are undesirable in the home vegetable garden.

Treatment options:

Ant mounds can be treated with boiling water, taking care not to disturb plants or allow hot water to contact them. Being very careful to avoid burning yourself or the vegetables, slowly pour about one-half to one gallon of boiling water into each mound.

Only certain insecticide products have been registered for treating ants in vegetable gardens. Follow label directions carefully and adhere to all days to harvest from treatment intervals indicated on the label when using a pesticide on and around food plants.

Granular bait products containing carbaryl (Sevin®) or carbaryl plus metaldehyde have been registered for ants foraging in the garden. The bait product Extinguish®, which contains methoprene, is now registered for use in cropland.

Fire ant baits containing the organic active ingredient spinosad may be applied directly in the garden and are even approved for use by organic gardeners (Ferti-lome Come and Get It; Green Light Fire Ant Control with Conserve and other brands).

Granular baits are effective fire ant control tools but are slow acting.

Most bait products are not specifically registered for use inside home vegetable gardens, but they can be applied outside the garden’s perimeter. To prevent fire ants from invading a vegetable garden, it’s very helpful to manage them properly in the surrounding landscape. Products registered for controlling fire ants in lawns and ornamental beds can be applied outside the garden perimeter. For best results treat two to three times per year, in spring, midsummer, and/or fall.

Liquid applications (drenches) of botanical insecticides can be used to control fire ants in vegetable gardens, such as d-limonene, pyrethrins, rotenone, pine oil, and turpentine. These generally low toxicity, plant-derived chemicals have various modes of action.

  • D-limonene is a citrus oil extract that kills ants quickly.
  • Pyrethrins, which act on the nerves, also kill ants quickly (within minutes to hours) and can be used as mound treatments or surface sprays.
  • Rotenone acts on respiratory tissues, along with nerves and muscles. Pyrethrins and rotenone products break down rapidly in the environment.
  • Rotenone and pine oil (turpentine) products are relatively slow-acting (days to weeks) and are applied as mound drenches.
  • Some brand names to look for include Citrex™, Insecto® Formula 7, Organic Solutions™ Multipurpose Fire Ant Killer, Organic Plus® Fire Ant Killer and others.

Finally, you can drench the hills with insecticide products labeled to control insects in vegetable gardens that contain the active ingredient permethrin, carbaryl or spinosad. Control problem mounds within the garden area by drenching with one of these insecticides. Mix and apply according to directions on the label. Use 1 to 2 gallons of drench per mound.

The information in this article is taken primarily from the LSU AgCenter’s publication on fire ant control and also contains information from a Mississippi State Extension publication (links below):

Managing Imported Fire Ants in Urban Areas
In this publication there are options for managing various kinds of imported fire ant problems.

Insect Pests of the Home Vegetable Garden
Some information, such as drenching mounds with spinosad, permethrin or carbaryl, is from this Mississippi State Extension publication.

Dan Gill
Consumer Horticulture Specialist

4/20/2015 10:05:08 PM
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