As we move into the spring season and the foliage begins to grow on plants, local residents are starting to notice pest activity throughout their landscape.

Irrigated ornamental and landscape plants that have been nurtured through this dry spell are prime targets for cutting ant defoliation.

Control of this South Texas pest is difficult. Many conventional control products that provide relief from numerous ants are not effective against this species that is capable of stripping a plant of its foliage overnight.

Texas Leaf Cutting Ants do not respond well to most ant baits. The lack of response is due to their feeding habits and life cycle.

The ants do not eat the leaf fragments they collect, but take them to their underground nest where they use the material to raise a fungus garden. As the fungus grows, certain parts of it are eaten by the ants and fed to the larvae. This fungus is their only known source of food.

Mating flights of Texas Leaf Cutting Ants usually occur after a heavy rainfall. After mating, the winged males die, while mated queens drop to the ground, lose their wings and dig small nests beneath the soil.

As the colony grows, worker ant numbers increase. With more workers to harvest leaf fragments, the size of the fungus garden is increased, allowing more ants to be fed.

Colonies can exist for years and may house over 2 million ants. Locally, leaf cutting ant colonies can be seen along roadsides, in open fields, in range and pasture lands as well as alleyways and yards.

Colonies can become quite large, covering an area up to an acre in size. Above ground, the colony is marked by numerous crater-shaped mounds, 5 to 14 inches high and 1 to 1 ½ feet in diameter. In heavily infested areas it is difficult to distinguish where one colony ends and another begins.

On the soil surface, leaf cutting ants have a clearly defined foraging trail. Ants will commonly travel 600 feet or more to reach plants to defoliate.

Considerable damage to a plant can occur in a few hours. Small to medium sized trees and landscape ornamentals can be stripped overnight.

Researchers in South America estimated that a large leaf cutting ant colony harvested 13,000 pounds of leaves over a 6-year period.

They also estimated that this same colony excavated more than 800 cubic feet of soil weighing over 44 tons.

Contact insecticides that contain the active chemical name: acephate, permethrin, or carbaryl, in powder or granular formulations, will temporarily protect plants.

Finding the mounds and applying these labeled insecticide products to the nest opening in a dust, granular or drench formulation will provide some relief from the pest, but it is very difficult to obtain complete control of large well-established colonies.

Continuous applications in accordance to label directions on these products is strongly recommended.

For additional information on this South Texas pest, come by the extension office, located at 729 E. Yoakum or visit the website at http://citybugs.tamu.edu/factsheets/ landscape/ants/ENT-1002/.