Aerial war against bird-killing mosquitoes on Kaua‘i underway

An airborne war against avian-malaria-spreading mosquitoes is actively underway on Kaua‘i, and soon to start on Maui.

On Kaua‘i, conservationists are flying a helicopter to spread a harmless bacterium in native forests inhabited by near-extinct honeycreepers, like the ‘akikiki.

The larvicide Bacillus Thuringiensis Israelensis (BTi) is a bacterium naturally occurring in soils and waterways. It suppresses populations of the species of mosquito that carries avian malaria. BTi is harmless to other creatures, including people, the Department of Land and Natural Resources stated in a press release Friday.

“It won’t affect any vertebrates like fish or birds, or your dog or your pig, or even you if you happen to drink water that this bacterium is found in,” explains Dr. Lisa ‘Cali’ Crampton, project manager for the Kaua‘i Forest Bird Recovery Project.

Since last fall, twice each month for three days at a time, a helicopter equipped with a boom with dozens of nozzles has flown up to a 1,200-acre parcel on the vast Alaka‘i Plateau to spray BTi over the forest and streams.

During a June briefing for the Board of Land and Natural Resources, Lindsey Nietmann, the forest bird recovery coordinator for the DLNR Division of Forestry and Wildlife, noted, “BTi has been used globally for public health and nuisance control of mosquitoes. It’s EPA-approved, and you can buy it over the counter. It can be applied by truck, handheld broadcast sprayer, or aircraft. We’re using a helicopter because we’re trying to target the millions of little pools of water in Hawai‘i’s rainforests, where mosquitoes can breed.”

The second phase of BTi work on Kaua‘i is underway now. The first phase last fall showed that water with BTi killed mosquito larvae at far greater rates than water without the bacteria. BTi applications are scheduled to begin on Maui after the first of the year.

“Like most mosquito control treatments, this is year-round suppression,” Crampton said. “We want to keep their numbers down to decrease disease transmission rates, so birds will not get infected as often by mosquito-borne diseases like avian malaria.”

She added that once you take the foot off the brake, the mosquito train will roll on. “So, we have to keep applying that brake.”

The Incompatible Insect Technique (IIT) is another tool currently being used to control mosquito populations on Maui. It will join the BTi arsenal on Kaua‘i next year.

“I think the tricky question in conservation right now is that there is such a crisis and there is such a demand on financial and other resources, we’re all trying to figure out the best way to deal with our huge problems,” Crampton said.

Is it BTi combined with IIT? “Is it bringing all remaining individuals of at-risk species into captivity until we can get landscape-scale mosquito suppression,“ Crampton wondered. “We need people to understand the importance of these tools and backing initiatives to employ all available tools.”

“It is to our benefit to do everything humanly possible to protect these birds. The tiny cost of this helicopter operation is worth it, compared to the catastrophic losses, economically and culturally, we would experience if we lost our native forest birds,” Crampton concluded.