Linda Hooper-Bui, Schultz, Bruce | 5/10/2006 1:48:36 AM
The destructive force of tidal surges from hurricanes Katrina and Rita at least had one benefit – controlling fire ants, according to researchers from the LSU AgCenter.
LSU AgCenter entomologist Dr. Linda Hooper-Bui recently said field surveys in the area of Plaquemines, St. Bernard and Orleans parishes area after Hurricane Katrina and in Southwest Louisiana after Hurricane Rita showed the fire ant population was far below normal in areas flooded by storm surge.
Some areas were void of any signs of ants, according to the researcher.
"Normally, if there were ants around, we would have seen them," she said. "If we searched and searched, we might find one."
Hooper-Bui said the meager signs of any fire ants were the case along the coast all the way to the Texas border. Ants became easier to find further north of the coastline, however, she said.
Lab testing shows that ants immersed in water with more than 3.5 percent salt, the concentration of seawater, lose their unique ability to form a ball-like cluster that allows them to survive flooding, the LSU AgCenter researcher said. Within 30 minutes, they get trapped under the surface of the water and sink, she said.
Water with only 1 percent salt causes ants to drown in 48 hours, she said. And even in salt-free water, ants can only maintain their capability of clustering for about six days.
"After six days, even in fresh water, the balls begin to break apart, and the ants begin to sink," she said.
The reason for the effect of salt water on the ants is unknown. Salt water has higher surface tension, so it seems that ants would have an easier time in a saline solution, Hooper-Bui points out.
Since fire ants are still around in many areas, however, Hooper-Bui said now is a good time to combat them.
The researcher said a new bait, an insect growth regulator called Esteem, has been developed and is effective at controlling fire ant populations especially in agricultural situations. The chemical also is sold for residential uses and is labeled as Distance.
Hooper-Bui said Esteem Ant Bait should be applied when ants are actively foraging, because ants are more likely to pick up fresh bait and take it back to the mound.
"It’s a really good compound," Hooper-Bui said. "It works a little faster than the other growth regulators. Esteem provides long-lasting control, because ants feed the bait to the queen and the developing colony."
She said Esteem reduces fire ant populations within three to four weeks, while the previous chemicals have required four to eight weeks.
"It’s best to use Esteem on areas where fire ants pose the greatest threat, such as calving areas, barns and hay storage facilities," she said.
Ants will begin flying soon to reproduce, Hooper-Bui said, so it will be important to be alert for new fire ant mounds to be treated before the end of May.