Invasive insects may be small, but they are driving research agendas at WPTRC in a big way. The little fire ant (LFA), Wasmannia auropunctata, was first found on Guam in November 2011 and identified by Dr. Ross Miller’s Entomology Laboratory, the ant identification center for the region. Since that time LFA have been found in many villages around the island, which may indicate they have been here much longer than previously suspected.
Fire ant is a generic term used for ants that have a very painful sting. Because of its small size, little fire ants swarm over their victims undetected and then sting en masse so that the ants appear to sting simultaneously. The effects of multiple stings can be lethal for small insects and animals that normally constitute the prey of LFA. On humans LFA stings normally leave an irritating rash that dissipates in a few hours, and in rare cases may trigger serious allergic reactions. Animals and birds stung in the eye may experience impaired vision or total blindness.
Miller’s lab is collaborating with the Guam Department of Agriculture in LFA control efforts at selected sites around the island. Sites were chosen for their ease of access and the density of LFA colonies. One control site is located next to the animal shelter, GAIN, in Yigo with two control sites in the southern part of the island. “There are several places along the road to Umatac that are heavily infested with LFA. Since the ant population is so large and well established, we believe they have been there for quite a while and were probably transported by people using the area as an illegal garbage dump,” said Miller. People have played an important role in helping LFA establish and move throughout the island, which is why LFA populations are found in villages from north to south.
The LFA team at UOG is currently treating six sites to verify techniques adapted for use on Guam from those developed in the Hawaiian Islands for controlling LFA. Detailed surveys are performed at each site to determine the magnitude and range of the infestation. The area is then treated with low toxicity granular bait attractive to LFA called Siesta™. A second insecticide that interrupts the growth cycle of the ants, Tango®, is sprayed on tree trunks and leaves. One week later the team conducts a follow-up survey to check the efficacy of the treatment, and then six weeks later both insecticides are reapplied and the site is again surveyed. Each site will receive a total of eight repeat treatments over a period of more than a year.
In a related study, USDA-ARS entomologist Dr. Sanford Porter in Gainesville, Florida is a leading authority on fire ants. Miller and Porter are collaborating to find a biological control agent for another fire ant infesting Guam and most Micronesian islands, the tropical fire ant Solenopsis geminata. Miller is sending several thousand live tropical fire ants to Porter who then exposes them to biological control agents collected from the ants’ home range in South America. The hope is that he will find an agent that efficiently attacks tropical fire ants under Guam’s environmental conditions without harming the few species of indigenous ants found on Guam.
WPTRC scientists in collaboration with local and federal agencies and experts around the globe are working to protect Guam’s cultural and natural resources.
Funded by US Forest Service