The little fire ant (LFA) is still steadily spreading across the island bringing its painful sting to all it encounters. Some homeowners in Umatac cannot allow their children to play outside as their yards are infested with these tiny ants. The good news is the treatments being used to control the ants are working and entomologists at the University of Guam, Western Pacific Tropical Research Center (WPTRC) are playing an active role in executing these treatments.
Dr. Ross Miller is finding success with his team’s implementation of LFA control techniques. The techniques were developed in Hawaii and adapted for use on Guam. Several of the sites, where multiple treatments were applied for one year, are now declared free of little fire ants. One site located in Yigo sits next to the home of the island’s only animal shelter, Guam Animals in Need.
With funding from USDA CAPS and US Forest Service, Miller’s team performed surveys at each treatment site to determine the magnitude and range of the infestation. The area is then treated with low toxicity granular bait called Siesta™. A second insecticide that interrupts the growth cycle of the ants is sprayed on tree trunks and leaves. One week later the team conducts a follow-up survey to check the effectiveness of the treatments, and then six weeks later both insecticides are reapplied and the site is again surveyed. Each site received a total of eight repeat treatments over a period of more than a year. “The only complication we have found is getting 12 straight hours without rainfall to apply the insecticides,” said Miller. “The treatment is working beautifully, but the ants continue to spread because of the indiscriminate dumping of LFA infested garbage and green waste.“
After typhoon Dolphin blew over the island in May 2015 there was a massive amount of green waste generated. Government of Guam officials opened a temporary green waste collection site at Oka point. Since that time, little fire ant has been found in the area around the collection site.
Miller’s lab is also involved with surveillance on the islands of Saipan, Tinian and Rota for coconut rhinoceros beetles and little fire ants to keep these invasive insects from hitching a ride from Guam to other islands. His team is using the locally created Coconut Rhinoceros Beetle DeFence Trap to monitor for the presence of rhino beetles.
Working with students in Costa Rica with the Native American and Pacific Islander Research Experience (NAPIRE) program, Miller has the opportunity to study little fire ants in their home environment. When comparing population density of LFA in Guam and in Costa Rica, Guam had a much higher density. This may be due to greater numbers of competitors and predators in LFA’s home range. This research highlights the vulnerability of islands when invasive species are accidentally introduced.
The impact of little fire ant on the ecosystems of Guam is not yet fully understood, but the work of WPTRC researchers proves that this invasive insect can be controlled.