With a high-pressure sprayer, CEMML’s Jaythan Lujan optimizes pesticide coverage for little fire ant control at Asan Ridge Overlook. Photo courtesy CEMML. BY JODI PETERSON
Imagine hiking through the lush jungles of Guam, catching glimpses of the serene Pacific ocean through the tangled foliage. You sit down on a log to enjoy the breeze—only to leap to your feet as tiny ants drop from the trees above, delivering painful, burning stings.
You’ve just encountered the little fire ant, a minuscule pest originally from South America. In tropical regions from Hawaii to the Caribbean, these ants are considered one of the world’s worst invasive species. Not only do they sting people and animals, they also infest agricultural fields, farms, and houses; promote other pests such as aphids; and are difficult to eradicate permanently.
On Guam’s western side, in the War in the Pacific National Historical Park, the National Park Service is treating an infestation of little fire ants with the help of CSU’s CEMML. Like the rest of Guam, the park has been invaded by harmful exotic species, including the brown treesnake and the little fire ant. The removal of these ants is key to a multi-agency program to restore native ecosystems and rare forest birds. The ants’ presence is detrimental to rare birds as it destroys avian food sources such as insects and larvae.
Describing how CEMML became involved in the eradication project, CEMML entomologist Ken Puliafico, Ph.D., said that the NPS reached out knowing that the organization has a lot of experience with controlling little fire ants and other invasive pests. “We had given presentations at professional conferences about our work,” he said, “and CEMML’s reputation for successful control projects is widespread.” He noted that while the organization most often works on Department of Defense lands, its expertise in natural and cultural resource management applies to all federal and state lands. “This project is a good example of CEMML taking skills honed by supporting the DoD into a new setting with new partners,” Puliafico added.
Starting in December 2025, the CEMML team began applying pesticides along the cliffsides and top of Asan Ridge, closing off access during spraying and for 24 hours afterward. “There are walking trails in the area we’re treating,” noted CEMML biologist Emily Selberg, “and groves of breadfruit trees that locals come and harvest.” To ensure that the breadfruit and the people who use it were not affected, as well as wildlife, the NPS reviewed pesticide labels and consulted with experts. CEMML’s licensed pesticide crew also took care not to harm protected species such as the Guam tree snail, an endemic vine, or native birds; and to keep spray well away from the ocean and creeks.
The park worked with Selberg to develop warning signs about the spraying in multiple languages, including CHamoru, the Indigenous language of the Mariana Islands, as well as Japanese, Tagalog, and more. “We are intentional about translating signs to multiple languages, which reflects the diverse visitors we have and the diverse activities they partake in— from sightseeing to food collection and traditional land use,” said Ella Norris, biological science technician with the NPS.
Next year, after additional treatments, results will be evaluated to determine if further control is needed. “It’s a small park, but we have big goals to manage and restore our natural resources in a way that benefits the community and furthers NPS goals,” said Norris. “Treating little fire ants is an important part of restoring native habitat and also makes the park safer for visitors to enjoy. Partnering with CEMML has a big impact on what we are able to accomplish to restore Asan Ridge.”