Phew!
There were no armies of little fire ants — among the world’s worst invasive species — in the latest spot surveys conducted in a 6-acre infestation zone in Mililani Mauka.
Agriculture officials announced this week they’ve seen signs of success in conquering the powerful little bugs, and a multiagency group has surveyed and completed the fifth of eight planned pesticide treatments against the ants.
Little fire ants had invaded two houses, stinging residents. Although one of the families said their young child had been stung a few years ago while in a crib, officials were first alerted to the infestation in June, said Becky Azama, Department of Agriculture noxious weed specialist, who engages in eradication work.
"While we are still guarded in our assessment, the fact that we aren’t finding ants indicates the eradication plan is working pretty well," state Board of Agriculture Chairman Scott Enright said in a written statement, calling the collaboration of multiple agencies, legislators, community associations and residents as "the foundation of this early success."
In May crews began treating a 6-acre area in Waimanalo, which includes a 3.5-acre property overgrown with brush and trees and a buffer zone around it.
Crews had to cut paths through the brush to treat the area.
The ants may be little, but the pain and welts they inflict, and the cost of eradication, could be enormous. If the ants become established on Oahu, that cost could reach $170 million annually in the next few years, one University of Hawaii study estimated.
The ants, which come from South America, are pale orange and can build large colonies in trees and other vegetation, on the ground, in buildings and in homes.
The eradication plan used in Mililani and Waimanalo was developed in part by Casper Vanderwoude at the Hawaii Ant Lab, Department of Agriculture entomologists and UH research scientists, and appears to be working against the generally nonaggressive, slow-moving bugs whose sting carries a painfully powerful punch that can even cause blindness in pets.
The Hawaii Ant Lab, Agriculture Department, Oahu Invasive Species Committee and Hawaii Invasive Species Council are involved in the survey and eradication efforts.
Crews treat lawns and common areas along the street side of properties, and shoot bait-type pesticide into trees.
They will continue to treat infestations every six weeks in the two Oahu areas. They will complete the eighth treatment in Mililani by March or April but will continue to monitor the area for the next two to three years, Azama said.
"We will have to start again if we find any," she said. "They’re so small, you miss one macadamia nut-full, they’ll be back again. It sounds scary, but you always have to be vigilant."
Azama said an "attack plan" was formulated depending on the situation. No chemicals were applied inside houses, but homeowners could choose to use pesticides safe for indoor use in their homes.
The crews verify reports of the ants and bait them with peanut butter, which contains the protein and fat they love.
They do a "delimiting survey" by blanketing the area with more vials of peanut butter in neighboring properties "to try to figure out where the edge is, where the boundaries are," Azama said.
Once confirmed, crews use Tango, a bait pesticide developed fairly recently by Vanderwoude that sticks to trees and does not break down in the rain.
The ants take the bait into their nests to feed their colonies. Tango is an insect growth regulator that prevents eggs from hatching.
This is far more effective than trying to kill only ants that are visible while billions remain in the nests, Azama said.
If Tango had been developed earlier, it may have been effective on the early infestations on the Big Island in wet areas like Hilo, Azama said.
At some Mililani houses the ants went after protein-laden dog food. In another case a trail of ants was spotted entering the house via service wires.
"The population was so high outside of the house, it was going inside," she said.
The ants are not aggressive compared with tropical fire ants.
"You could put your hand in a nest" of little fire ants and they won’t sting, Azama said. Stinging usually occurs when they get trapped in your shirt collar.
The ants live wherever they can get moisture and food, often in tree trunks and inside banana and ginger plants where moisture and debris collect and aphids live. The aphids also excrete honeydew, a sugary substance, which the ants eat at certain times of their lives.
Maintaining a clear area and removing leaf litter will help, Azama said.
The ants were first discovered in Mililani Mauka in June by an Auina Street resident. Surveys found they had spread to homes on Auina and Kopalani streets on both sides of a gully.
Little fire ants were found on Hawaii island as far back as 1999. They were detected in late December 2013 on hapuu logs at retail stores on Oahu and Maui. Small infestations were discovered at five Oahu nurseries, three of which were in Waimanalo. They were treated and cleared of ants, the Department of Agriculture said.
Infestations were discovered in January on Maui in five to seven properties in Huelo and on one Haiku property, agriculture spokeswoman Janelle Saneishi said.
