Hello Tim,

Sounds like you have mound ants, Formica spp. (Hymenoptera: Formicidae).  Mound ants are very difficult to control and insecticides offer your only hope of doing so.  That said, they are likely helping to keep your garden pest-free.

Mound ants, Formica sp., build large conspicuous nests in open fields and in open areas in woodlots and forests. Their large mounds are constructed of soil brought up from excavated galleries below the nest. Large colonies may include over 250,000 workers and over a 1,000 egg laying queens. The mound acts as an incubator for mound ant larvae and pupae. The ants kill nearby vegetation including small trees and shrubs to keep shade off of the mound. They do this by chewing a small hole in the bark and injecting formic acid into the wound. Not surprisingly, they can be a real pest in nurseries and Christmas tree plantations. They will often aggressively defend the mound by biting those who dare to disturbed it. This can make life very unpleasant for those who happen to share their yards with mound ants. Mature mounds may reach over 30 inches in height, six feet across and the subterranean galleries may go to a depth of six feet beneath the ground. The nest’s size and depth make them very difficult to kill off.

Mound ants feed on most any type of small insect or arthropod that they can find as they forage or hunt over the ground. The ants also collect the honeydew secretions from sap-sucking insects such as aphids and leafhoppers. They rarely enter homes or buildings in search of food, which a very good thing. They are pretty much harmless. They don’t bother people or pets unless the mound is disturbed.

If you feel you must kill off the ants, then dusting the top of the mound and around the perimeter with an insecticidal dust like Sevin Garden Dust and then raking the top of the mount can be effective if repeated enough times. Raking the mound causes the ants to move to the surface to repair the damage to their galleries. The dust is picked up by the ants and spread throughout the colony. Repeat this process until no more activity is observed. Keep in mind that because of the colony’s large size and the determination of its occupants, mound ants are very difficult to control.

Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide.

Best regards,

Howard

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Answers...

I do battle aphids and have been told that ants play a role in bringing them into the garden. Do you know this to be true? They don't bring aphids to the garden, but they do tend and protect them from other predators.

Might there be other downsides to their close proximity to the garden that you know of? Not really, although some might consider them a nuisance.

If I do go the route of using sevin, which I am hesitant to bring chemical treatments near my vegetables, in your opinion how safe is the Sevin dust to have around food sources or in the earth nearby? Sevin is relatively safe to use, in fact, it is labeled for use directly on vegetables.

Would you happen to know the half life of Sevin? I don't know the half-life of Sevin.  You can view the label at .. https://www.gardentech.com/products/sevin/-/media/A89749E4FDF840A<personal data hidden>BFD3662.ashx

Hope this helps,

Howard