While no one has yet translated the depredations of red fire ants into dollars, state highway departments already rate them a serious menace. The ants like to infiltrate traffic control cabinets where they get inside the flasher controls and strip insulation from control wiring, causing short circuits, which can result in potential tort liability claims. A service call to repair the damage averages $200.
In Texas, which has 15,000 traffic signals, a study conducted for the Department of Highways by Texas A&M University estimated that controlling the ants with insecticides would produce annual maintenance savings of $600,000.
The ants also have been a major factor in air conditioner failures. Service personnel in Texas have reported that fully one third of all summer repairs stem from ants shorting out terminal blocks. They also have been found to have set up housekeeping in televisions, well pump controls, telephone junction pedestals, airport runway lights, utility watthour meters, electrical plugs and lamp sockets, computers, and transformers-where they prefer to nest on the high-voltage side.
Why are imported red fire ants attracted to electric fields? No one is yet ready to offer a theory. But biologist Dr. William P. MacKay of the University of Texas at El Paso and entomologist Professor S. Bradleigh Vinson of Texas A&M have succeeded in eliminating a number of possible factors.
They have found fire ant behavior does not correlate with a-c frequencies, or with the presence of ozone, electromagnetic or magnetic fields. Nor is the type of insulation used on wiring a factor. In tests up to 140V a-c and 350V d-c, both attracted almost the same number of ants at the same voltage and distance. However, they did find that when electricity was turned off, ants attracted to d-c power dispersed more rapidly than those who had been experiencing the nirvana of an a-c source.
While the Texas researchers still don't understand the reasons why the ants have a fatal attraction to electric fields, they have been able to devise successful control techniques. Based on their studies, they recommend using terminal cap protectors to prevent bridging, and denying entrance to the insects by enclosing mechanical relays in metal or plastic cases and sealing them, as well as all entrances to padmounted equipment, with epoxy cement. In laboratory tests, silicone rubber sealants and roofing cement proved ineffective.
MacKay and Vinson also recommend applying insecticide annually to the interior of electrical equipment cabinets. While 157 chemicals have been registered as fire ant controls, they have tested three commonly used insecticides: 1,1,1 Trichloroethane; a combination of pyrethrin, piperonyl butoxide, and silica gel; and chlorpyrifos.
)
