Kauaʻi Forest Users

Project description

The Alaka’i Wilderness Preserve is home to unique and rare forest birds that are declining at alarming rates. Recent data show that ‘akikiki are nearly extinct in the wild and ‘akeke’e and other honeycreeper species are reaching perilously low population numbers due to avian malaria carried by invasive mosquitoes. To control avian malaria, DLNR Forestry & Wildlife and the Kauaʻi Forest Bird Recovery Project are controlling mosquitoes over large areas of the Alakaʻi Wilderness. One approach involves aerial application of a highly mosquito-specific bacteria that controls mosquito larvae called Bti, derived from the bacterial strain Bacillus thuringiensis israelensis. Bti has been used for more than 30 years as an environmentally safe and effective larval control tool in sensitive habitats and even in organic agriculture. It only affects larvae of mosquitoes and close relatives such as blackflies and does not affect other insects, wildlife, or humans.

While Bti is often applied by hand to small water bodies while walking through a forested area, it would be impossible to cover enough area on foot to protect ʻakikiki and ʻakekeʻe habitat across the Alakaʻi Wilderness. Aerial application of Bti products has been used extensively for control of human disease, and this year we have successfully adapted this methodology for Hawaiian forest environments over a small pilot treatment area of 270 acres. Preliminary results show that droplets of Bti product applied from helicopter-mounted sprayers reach the forest floor in sufficient quantities to kill mosquito larvae. We have secured funds to expand the treatment area to ~1000 acres in the mid-Koaie drainage to provide more control of mosquitoes and avian malaria to protect forest birds from June 2024 through March 2025. Treatment will occur approximately every two weeks over several days for a couple of hours at dawn and dusk. Planned application dates are listed below, but are subject to change due to weather and other operational factors.

Bti is a different, complementary tool from the Incompatible Insect Technique, commonly known as mosquito birth control. IIT uses a different bacteria (Wolbachia) to reduce the amount of viable mosquito eggs produced in the wild. You can learn about different mosquito control tools and which are (and are not) used in Hawaiʻi from our partners at Birds Not Mosquitoes.

You can also find additional information in this Bti FAQ produced by DLNR and Kauaʻi Forest Birds, or from this story on KITV.

Planned application dates for summer and fall 2024 (subject to change due to weather or other factors)