Sweet Gum Tree & Ants

Sweet gum trees (Liquidambar spp.), beautiful, large trees, grow in U.S. Department of Agriculture plant hardiness zones 5 through 10, depending on the species. Like many large trees, sweet gums are tough once established, but experience chronic problems with aphids and scale insects, both sap-feeding pests. Unfortunately, ants are feverishly drawn to trees with sap-feeding insect infestations. Getting rid of the ants on a sweet gum tree requires a two-pronged approach that controls both pests at once.

Aphids and Scale Insects

Aphids and scale insects are both relatively immobile, sap-feeding insects that feed voraciously on the juices inside plant leaves and shoots. Tiny, soft-bodied aphids often feed in clusters on the undersides of leaves. Scale insects frequently look like bumps or unusual growths on trees, blending in along stems and on both sides of the leaves. Both of these pests produce a sticky substance called honeydew when they feed.

Ants and Honeydew

Ants are attracted to aphids and scale for the nutritious honeydew they produce. Ants have been seen caring for these pests, stroking them and carrying them to new areas to encourage their continued honeydew production. The sap-feeders give the ants an endless supply of food, and in turn, the ants provide them with protection from predators that would normally keep their numbers in check.

Sap-Feeding Damage

Aphids and scale insects cause similar damage to trees, with leaves most often affected. They may discolor, curl, dry out or fall off due to the stress these pests put on them. Tender growth that has been fed upon by aphids or scale insects may emerge twisted or stunted. In addition, the sticky honeydew attracts sooty mold colonies that may grow so thick that they interfere with photosynthesis.

Aphid and Scale Insect Control

Fortunately, aphids and scale insects are reasonably easy to control, if you are persistent. On small trees, repeated, thorough applications of insecticidal soap or horticultural oils will quickly eradicate sap-feeders, but larger sweet gum trees may require more drastic control methods. While you can trim infested sections from the tree, systemic insecticides, like imidacloprid, can be used on non-food plants like sweet gum to destroy pests as they feed.

Ant Control

You'll need to keep the ants out of the sweet gum tree while you work on controlling aphids and other sap-sucking insects. If your tree is trimmed so there are no alternative access points, apply a 2- to 3-inch-wide sticky barrier on the trunk, 2 to 4 feet above the ground, to prevent the ants from moving the pests to other feeding sites. Placing several bait stations stocked with sweet ant bait at the base of the affected tree will gradually eliminate the entire ant colony.

About the Author

Kristi Waterworth


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