The Q&A Archives: Safe eradication of ant infestations

Question: I have been working on developing a woodland/shade garden at the edge of my property that connects to woodlands. I recently noted that plants are being eaten by insects/dying and found several ant infested areas. I suspect this is the problem. Since this area is home to birds, chipmonks, squirrels, etc., what could I do to safely deal with the problem and where might the remedy be obtained? I'd also appreciate learning of additional resources for a woodland/shade garden.

Answer: Having ants in your plants isn?t as bad as it may seem. Ants are, for the most part, very beneficial insects in our gardens and landscapes. They help till the soil, decompose dead plant and animal matter and even destroy some small insect pests.

Ants are literally everywhere outside, and their ground nesting habit creates beneficial cracks and crevices that improves our soil by loosening it. Water flows more easily into the ground where ants have been working. Oxygen from the atmosphere, also has an easier time diffusing into the soil, and this oxygen is also critical to healthy plant growth. Plant roots also use these ant created soil ?channels? to grow in and through.

In addition to controlling some small insect pests of gardens and landscapes, ants are excellent indicators of the presence of pesky garden aphids. Many ant species feed on the sticky-sweet secretions of aphids called ?honeydew?. If you see large numbers of ants crawling up your roses, oleander, bougainvillea, flowers or vegetables, chances are they?re slurping up the honeydew from active aphids. Follow the ants and you?ll find the aphids. Then you can spot treat the aphid populations with a simple soap spray made by mixing one teaspoon of liquid dish washing detergent in one pint of water.

Contrary to popular belief, ants do not eat plants! They cannot digest the cellulose in plant tissue. There is one kind of ant that seemingly eats plants - but really doesn?t. It?s the leaf-cutter ant, and it cuts leaves of various plants to grow it?s ant garden. These interesting little creatures use leaf pieces to grow a specific type of fungus underground in garden cells they create. They paste the leaf pieces with their saliva to grow a special fungus that converts the plant cellulose to form of carbohydrate the ants can eat. The ants actually tend their garden by destroying other fungi and pests that would compete with or damage their food fungus. As new leaf pieces are brought into the nest, they are cut up, pasted and ?seeded? to grow more fungus.

As leaf-cutter ants feed specifically on this fungus, they will not take ant baits. The only way to prevent the damage caused by the leaf-cutters stripping plants bare of their leaves is to create a physical barrier. But, contrary to the advertisements, sticky, vaseline-like products pasted on the trunk base will not work! The leaf-cutter ants simply build bridges using their stuck friends to cross over the sticky goo.

To prevent ants from climbing your plants, try a barrier of a slick, smooth material like sheet metal or aluminum foil. This will prevent the ants from being able to grasp onto something to climb. Place a 4 inch band of metal or foil around the trunk or stem at the base, just above the ground. If you choose foil it must not be smooth, not crinkled, as the ants will use the creases for traction. Secure the bottom and top of the barrier band so that ants can?t crawl between it and the bark. The edges of sheet metal can be caulked. Aluminum foil may be secured with rubber bands or tape. Keep the band clean by spraying it off with water now and then. If dust and dirt accumulates on the band barrier, the ants will be able to grab on and crawl across the band.

For the most part, plants stripped of their leaves will leaf back out in a relatively short period of time. Most trees and shrubs can handle being defoliated several times before real injury develops. Just make sure these plants have adequate water. A small amount of nitrogen fertilizer will also promote the growth of new leaves.

Numerous ant species will be attracted to moist, shaded conditions underneath potted plants setting on patios. This is a particular problem on patio pavers set in sand. The ants come up through the joints, directly from the ground and may begin nesting inside your pots. To prevent this, simply place your pots on ?pot feet?. These little clay devices can be found at most garden supply stores. They elevate the pot an inch or two off the patio surface. This provides an air barrier under the pot and keeps the patio surface dry, thus eliminating the dark, moist conditions ants love.

For additional information on woodland plants in Pennsylvania, try the native plant society website:

Best wishes with your garden!

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