Invasive little fire ants have infested about 20 acres of forest in Nahiku, Maui, according to the state Department of Agriculture.

The ants were discovered in the area on Sept. 18 when personnel from the Maui Invasive Species Committee were repeatedly stung while attempting to eradicate miconia, an invasive plant.

On Thursday, Agriculture Department personnel visited the area and confirmed that little fire ants had infested a large swath of forest along Hana Highway.

The Nahiku site is the largest area of little fire ant infestation yet discovered in Hawaii. The department is working with the invasive species committee and the Hawaii Ant Lab to develop treatment plans for the site.

Little fire ants are native to South America and are considered among the world’s worst invasive species, according to the department.

They were first detected in the state on Hawaii island in 1999. Since then, they’ve been detected on Maui and Oahu. Last December, little fire ants were found at seven Oahu nurseries.

The ants have also been found this year at hotels in Wailea, Maui; in hapuu logs originating from Keaau, Hawaii island, and shipped to Maui; and in Mililani and Waimanalo. Inspectors on Maui also found little fire ants in the crowns of specialty pineapple shipped from Hawaii island.