UMass Extension Turf Program

Ants in Lawns

Fact Sheet Category: 
Insects

Many species of ants invade lawns throughout New England. Ants normally prefer dry, well drained soils which have a low water holding capacity. They can be pests in turfgrass areas because they build mounds which are unsightly. In the process of building tunnels, they can break off roots and root hairs or increase the desiccation of the soil. In addition, the turf in the affected area may become thin and unattractive. Large mounds can also smother grass and even damage lawn mower blades.

Adult ants have a narrow, constricted “waist” connecting the thorax to the abdomen. There is a wide range of colors, from yellow to red to brown to black, and an equally wide range of sizes, from 1/16-inch to 3/4-inch, depending on the species. Larvae remain underground in the nests and are white and legless, tapering slightly from the head to the tail. The species which appears to be most common in New England turf settings is Lasius neoniger.

Most ant mating activity occurs during the summer months. A newly mated fertile female will shed her wings and burrow into the ground to begin constructing a nursery chamber, where she will lay a few eggs and tend them herself. These eggs will hatch into workers (wingless females), which then take over the maintenance of the colony. The queen’s chief purpose then becomes to produce more eggs, which hatch into soldiers or workers, which construct and repair the nest, gather food, feed the immatures, and defend the colony.

Many ants are predators on other insects, and so provide the benefit of biological control of certain pest insects. However, ants can be a nuisance in their own right. Ants are generally negligible pests on home lawns and seldom cause a loss of vigor to moderately maintained turf in New England. However, there may be instances in which population levels rise and activity causes unacceptable turf damage.

Traditional insecticides appear to be the only control option available for ants at this time. One key to success is to make the initial application as soon as surface activity becomes apparent (often early May). Field studies indicate that some insecticides do not kill these insects, but instead induce them to move away. However, applications made directly to the mound enhance the effectiveness of the material. While mound directed applications take longer to complete, they reduce the amount of pesticide used and the likelihood of misapplication. As with any pesticide application, be sure to read and carefully follow all label directions.

Bear in mind that ants have many natural enemies, including a variety of insect predators. If a broad spectrum insecticide is used to clean up an ant problem, it may have a detrimental effect on the natural predatory insects which help behind the scenes.

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Written by: Dr. Pat Vittum

Revised: 05/2011