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University of Illinois Extension

Ants

Ant hill

Ant hill  

Frequency

5 (1 = rare 5 = annual)

Severity

1 (1 = very little damage 5 = plants killed)

Hosts

Ants and anthills may appear in maintained turfgrass as well as in ornamental planting beds.  

Symptoms

The tunnels of anthills serve to loosen the soil, allowing air and water to more easily enter. Small numbers of turfgrass plants may die as a result of the removal of soil near the roots and the drying out of roots where an anthill is constructed. Some species of ants will construct large anthills that may kill the turf in a 1- to 2-foot diameter and stick up into the air high enough to be hit by mowers. Ants' scavenging activities help to recycle nutrients back to the turf.  

Life Cycle

Although ants are familiar to everyone, they can be identified by their very obvious 3-body regions of head, thorax, and abdomen. Ant antennae are elbowed, having a sharp bend about a third of the way out from the head. There is a very obvious constriction between the leg-bearing thorax and the abdomen that is the hindmost large body area. This constriction produces an hourglass-shaped waist that will have a bump, node, or sharp-angled structure on it. The combination of these characteristics will separate ants from other insects.

Ants live in colonies which are most often seen in turf as anthills, each being a hole in the ground that is about 1/4 inch in diameter with a mound of fine soil around it that is usually 2 to 3 inches in diameter. Each colony has several classes or castes of individuals. There will be 1 or more wingless queens that are usually the largest ants in the colony. Queens lay the eggs that keep the colony going.

Usually two or three times a year, winged males and females called reproductives emerge from the colony. This will occur in all of the colonies of the same species on the same night. These winged ants look like the wingless worker ants except that they are larger and have 2 pairs of wings; the first pair is much larger than the second. These winged reproductives mate and then select a site to start a new colony. They shed their wings and tunnel into the soil to construct a new anthill.  

Management

Large anthills can be killed by opening up the top of the anthill to expose the tunnels and then applying a recommended insecticide into the colony. Within a few weeks a new anthill will likely appear in the area, but it will probably be an ant species that will not build such a large anthill. Even small anthills may warrant control on golf-course greens. Ants and their anthills may need to be controlled with an insecticide application where new sod is being laid because their tunneling activities under the loose sod will allow the roots to dry out and reduce the likelihood of the sod's surviving.

Attempting to control small anthills over an extended time in turf is not recommended. Ants are so numerous that areas where the anthills have been killed with an insecticide will be colonized by new ones as soon as the insecticide residue degrades, usually in about a month. Repeated control efforts will result in recolonization of the areas with ants. If there is no other reason for avoiding general ant control in turf, the fact that control is so short-lived against an insect that causes no apparent harm should be reason enough.


Filed under plants: Turf

Filed under problems: Insects Damage

More information is available on Hort Answers.