Little ant birth control finding big success on Maui

HONOLULU (KHON2) — A huge win for conservation was what invasive species experts said after efforts to eradicate the largest infestation of little fire ants on Maui found success.

“We can not find them,” said Maui Invasive Species Committee (MISC) invasive ant supervisor Brooke Mahnken said, “so, you know, it looks like we really have done it. We’ve gotten rid of the ants.”

There is a massive improvement in Nahiku almost a decade after the little fire ants were discovered there in 2014. MISC said the insects — which are about as long as a penny is thick — were seen across 175 acres, but there was no exact count.

“But, you know, somewhere around a billion or more little fire ants in that area,” Mahnken said of the 2014 situation.

The critters can damage crops, sting workers and are known to cause blindness in pets and livestock. Experts said only queens can reproduce, while worker ants bring her food.

“But in just one acre, there can be thousands and thousands of queens,” said Coordinating Group on Alien Pest Species program manager Christy Martin, “all living in their little tiny pockets of a tree and that vegetation and the challenge then is, how do you get every single queen in that acre?”

Rather than finding and killing each queen, Mahnken’s team developed a first-of-its-kind method of delivering gel bait mixed with an insect growth regulator — a type of ant birth control — by helicopter.

“With a big line hanging down and this spray bottle at the bottom, squirt this bait all over the tops of the trees, down to the ground,” Mahnken said, “the workers go out, they find the bait, they bring it back and they feed it to the queen and as long as the queen is fed on a regular basis, she will not be able to reproduce.”

Mahnken said the bait is not toxic to crops, or even to the ants themselves.

“They’re actually dying of old age and the queens can live for a year or maybe two years. whereas the workers are much shorter lived. They have a life span of several months,” he said.

His team has been delivering bait via helicopter since 2019. Follow up surveys will be done to ensure none were missed, but experts said Nahiku is a beacon of hope for Hawaii since there are active little fire ant infestations on every island except Lanai and Molokai.

“This is the very smart [way], knowing the biology of the ant and using the biology to control them, using the workers to get that dose — that once-a-month dose — to the queen, that eventually works,” Martin said.

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