Moth Introduced on Maui in Biocontrol Against Fireweed

Maui ranchers Greg Friel of Haleakala Ranch, Jeff Alexander of Anuhea Ranch, Gerard Thompson of Thompson Ranch and Darcy Oishi, HDOA entomologist take a close look at the fireweed moth larvae that eat the leaves and stems of the fireweed plant. Photo courtesy Hawaii Department of Agriculture.

By Wendy Osher

A moth was introduced on Maui yesterday as a biological control insect in a battle against the invasive fireweed plant, which is considered highly toxic to cattle and horses.

State agricultural officials say the Madagascan fireweed moth is the state’s “best hope” for controlling the fireweed which authorities say has taken over more than 850,000 acres of pastureland, mostly on Maui and Hawai’i Island.

Officials with the state Department of Agriculture say 50 moths and 500 caterpillars were released at Haleakala Ranch on Thursday, with an additional 2,000 larvae and moths given to ranchers for distribution and release at 10 other island ranches.

Fireweed, photo courtesy Hawaii Department of Agriculture.

“The benefits of finding a suitable biological control for an invasive species is that it works continuously and it works for free,” said Russell S. Kokubun, chairperson of the Hawaii Board of Agriculture in a press release.

Kokubun said the entomologists carefully researched the fireweed moth to make sure that it would only feed on the invasive fireweed. State agricultural officials say more than 13 years of research preceded yesterday’s release.

Darcy Oishi, the Biocontrol Section Chief for the HDOA said gauging the impact of the fireweed will take a while.

Photo courtesy Hawaii Department of Agriculture.

“There’s so much fireweed out there, it’s like a massive buffet for the larvae,” said Oishi in the media release detailing the biocontrol release on Maui.

State officials noted that although there are effective pesticides to combat the spread of fireweed, they called the use of them “cost-prohibitive and impractical” due to the expansive acreage where the plant is found.

Officials from the Hawaii Department of Agriculture say they are also testing four other potential natural enemies of the fireweed.

The moth introduction on Maui comes on the heels of a similar release conducted at Kahua Ranch on Hawai’i Island last month. Agriculture officials say more releases are planned on both islands.

Fireweed, photo courtesy Hawaii Department of Agriculture.

Fireweed Caterpillars, photo courtesy Hawaii Department of Agriculture.