Maui officials say fire ants still pose a significant threat to the island even though fewer have been seen since the start of this year.

The Maui News reported Thursday that public complaints about the invasive insects have slowed since January.

Maui Invasive Species Committee Manager Teya Penniman says officials will be in watch mode on an ongoing basis because the ants will keep coming from the Big Island unless they’re stopped.

An infestation at Maui garden shops in December was traced back to shipments of Hawaiian tree ferns at two home improvement stores. Customers who bought the plants were asked to check their homes for the ants.

The ants have been a problem on the Big Island for 15 years. They threaten agriculture and tourism.