Fire ants!

Asked July 2, 2015, 4:16 PM EDT

How do I keep fire ants from eating my plants and vegetables. I've purchased different types of pesticides and placed it directly to their mounds but they just move and now they've discovered my plants. Specifically, they're eating the blossoms off of my lavender plant. Is there anything I can do to protect the plants I have now and future plants I plan on bringing in?

Contra Costa County California

2 Responses

Imported fire ants will often damage plants, especially during periods of dry weather. They will also "farm" aphids to collect the honeydew they produce to feed their colony, but when farming aphids, they usually do not also damage the plants. It is best to find the source of the foraging ants (their colonies or mounds) to limit their damage to you home garden plants. Once the colony(ies) has(have) been located, you will want to control that colony. There are baits in the marketplace that can be effective, but you might want to consider drenching the mound with an insecticide mixed in water. Make sure the insecticide you use is one that is approved for use in home gardens. Do not use acephate (Orthene) that is commonly recommended to control fire ants. It is systemic and might be taken up by the plant if the mound is actually located in your garden. Use a common watering can. Mix the insecticide as the label recommends for use in the home garden in water in the can. Then drench the mound by pouring the liquid first around the mound and working inward to eventually drench. The bigger the mound, the more liquid that is needed to completely drench it to achieve total control. If the mound moves, retreat. There is no proven method of treating your plants to protect against the ant damage.

To whom it may concern,

I suggest you seek an identification of your ant pest species. Free pest ID services can be obtained in your county from the UCCE Master Gardeners and the Department of Agriculture:

Red imported fire ants have not been reported from Contra Costa County. More likely, you are dealing with Argentine ants or another common outdoor species. It is also possible that the ants are feeding on honeydew produced by a piercing-sucking pest such as aphids or scale insects rather than the plants themselves. Visit this University of California resource to learn more: