Neighborhood Age May Be A Factor In Fire Ant Infestations

by Nathan Riggs, Extension Agent – Integrated Pest Management

Texas Cooperative Extension, Bexar County (August 2001)

The age-old question when dealing with fire ant-related problems has always been, “What is the best thing I can use to get rid of those mean little things?” The best answer is that natural enemies of the fire ant (other ant species, for example) hold the greatest promise in winning the daily battles between homeowners and the hoards of stinging fire ants in their lawns. The problem with natural enemies is that they are slow to develop because it takes years of research to determine what effect, if any, they have on non-target insects, and if they can even become established in the area where they are released.

In the interim, pesticides are our best tool for reducing fire ant populations below problematic levels. The best use of pesticides occurs when neighborhoods band together and battle their fire ant infestations as a group. When neighborhoods utilize this technique, pesticide applications can actually be reduced by up to 75% and as much as 80% less money is spent on fire ant-related expenditures.

Several San Antonio neighborhoods have tried this area-wide approach to managing fire ants and met with tremendous success. Two such neighborhoods have provided some insights into how fire ants can be managed at a neighborhood level.

Jade Oaks neighborhoodThe Jade Oaks neighborhood is located in northwest San Antonio off of Prue Road. The oldest homes in the neighborhood are 3 years old with the last construction completed in January 2000. The majority of lots possess very little shade and newly-sodded lawns. With the last home just recently completed, the area is still considered ecologically disturbed. All of these factors – construction, new turf, and little shade – provide ideal conditions in which fire ants flourish. Disturbance causes other ant species to leave the area, leaving no resistance to fire ant invasion. As a result, the average lawn in Jade Oaks contained 4.7 mounds. Biological surveys in the neighborhood revealed that only 3 other species of ants lived in the area and their numbers were too low to repel fire ants. In September of 1998, Jade Oaks conducted a neighborhood “Fire Ant Day” providing the 91 homes in the area an opportunity to treat their lawns and begin the process of reducing fire ant populations. Eighty-five homes were treated with a popular fire ant bait insecticide at the broadcast rate of 4 oz. per lawn. Cost of application for each home was $5 and took 5 minutes to apply. Mound counts and biological surveys in the Fall of 1999 showed that fire ant mounds were not found in any lawns and that small numbers of native ants were still present in the neighborhood. Another “Fire Ant Day” was held in May 2000. Participation was much lower because the overall fire ant population in the neighborhood was almost non-existent.

Countryside NeighborhoodAn example on the opposite end of the scale is the Countryside Neighborhood located just north of the airport off of Bitters Road. The Countryside Neighborhood is at least 25 years old with established shade trees and no construction. The ecological system in the neighborhood is considered very stable. Biological surveys and mound counts in the neighborhood found at least 13 species of ants (including fire ants) and averaged a much lower 0.1 mounds per lawn. The homeowner association in Countryside contracted with a local pest control company to treat all front lawns in the neighborhood at a cost of $6.42 per home. The association paid for the treatment, so no direct costs were paid by individual homeowners. Of 190 homes in the neighborhood, 187 were treated in late April 1999 with a broadcast application of commercially available fire ant bait made by a pest control operator. Surveys in the Fall of 1999 revealed that mound counts had not changed after treatment and that other ant species were not harmed by the bait application. The abundance of other ant species throughout the Countryside neighborhood is a prime reason for the lack of fire ant infestation. As of right now, other ant species are the best natural enemy available to combat fire ants.

What does this mean for neighborhoods? Although there have been no statistical studies comparing fire ant infestations in established and newly constructed neighborhoods, it is apparent that there are differences. Older neighborhoods appear to have less fire ant infestations possibly because of the stability of the ecosystem, while the disturbed ecosystem in newer neighborhoods provides an easy target for fire ants to invade.

What does this suggest that one should to combat fire ants in one of these neighborhoods? Simply that homeowners need to assess what kind of fire ant problem they have before making a management decision. If there are 5 mounds or less in the lawn, then only the mounds should be treated (with whatever the homeowner likes to use). This method protects the ant species that provide the only resistance against fire ant invasion. If there are more than 5 fire ant mounds in the lawn, a broadcast application of fire ant bait insecticide at the rate of 3 to 6 oz. of bait per average urban lawn, or 1 pound per acre for larger lots, will provide an 80 to 90 percent reduction in fire ant mounds within 2 to 8 weeks after application. These baits will affect other species of ants, but in situations where there are many fire ant mounds, there aren’t many other ants present to affect.

Neighborhood age and ecosystem appear to affect the population status of fire ants in an area. Knowing this information can help homeowners design fire ant treatment strategies for their own lawns as well as their neighbors’. This information has allowed many San Antonio neighborhoods successfully combat fire ants on an area-wide basis in a very cost effective and environmentally sound manner.

NOTE: This information is taken from research studies conducted within these neighborhoods. More research is being done to support these hypotheses.

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