Farmers, ranchers receive moths, larvae for fireweed

PUKALANI – Maui farmers and ranchers on Thursday converged on Haleakala Ranch, where they received more than 2,500 Madagascan fireweed moths and larvae that they hope will rid their pastures of a plant toxic to their animals.

It marked the first of hopefully many mass organized distributions by the state Department of Agriculture and releases by the farmers and ranchers on the Valley Isle.

“The goal is to have production primarily on the Big Island and Maui, so Oahu can focus on further research,” said Darcy Oishi, Agricultural Department acting plant pest control chief.

The fireweed has infested more than 400,000 acres of rangeland in the state, with the majority of the plant found on the two islands. The non-native plant has caused difficulties for ranchers due to its toxicity, which can poison live-stock.

“This is a major problem for both Maui and the Big Island,” said Alex Franco, president of the Hawaii Cattlemen’s Council. “The only way we can control this invasive plant is through bio-control.”

After studying the insect and its possible effects on Hawaii’s ecosystem for 13 years, the bio-control measure was approved for use by the state in December.

At the ranch, plastic containers holding a fireweed plant and about 50 larvae each were brought from Oahu. The total of about 50 containers will be distributed to ranchers.

There also were a few containers that held adult moths that will be released on Maui ranch land.

Oishi said many containers with larvae had plants that were completely devoured overnight and needed to be replaced in the morning.

Joe Santos, who works for Kaupo Ranch on Haleakala, took four containers holding the “eating machines” and plans to place half of them near sea level and the other half at about the 6,000 foot elevation on the ranch.

In his three years on the ranch, Santos said, he has seen fireweed become a major problem and hopes the release of the fireweed moth will help decrease its prevalence.

Lifelong rancher Gerard Thompson, who owns Thompson Ranch in Kula, said that the invasive plant is not a major problem on his ranch yet but said it could be problematic when coupled with the lack of rain and the drought-resistant qualities of the fireweed.

Thompson grabbed one container and said that he plans to place the larvae in a heavily infested area near his house and “see what happens.”

Oishi told the ranchers to be cautious about the areas where they place the insects, telling them to look for heavily infested areas with relatively tame winds.

Rob Curtiss, the Agricultural Department’s entomologist in Kona, agreed with Oishi, saying that the environment is an important part of the process. Ranchers in Kohala who cannot avoid heavy winds have built cages out of angle iron and PVC pipe anchored down, he said.

“Basically any building material,” Curtiss said of the material for the cages. “It’s really variable in who is building it and how they want to build it. We’re just seeing what works.”

He stressed that the cages were important, because they help fireweed moths find mates in the confined enclosure and establish the population in the area. The cages are supposed to be placed on a large growth of fireweed.

Greg Friel, livestock manager at Haleakala Ranch, said his ranch converted an old milk farm into a breeding facility for moths with three full-containment cages. The ranch got its first shipment of larvae about a month ago.

He said that the older fireweed larvae have reached the cocoon stage and the ranch plans to take them into its pasturelands in the next few weeks.

The Agricultural Department, in conjunction with the University of Hawaii and the Hawaii Cattlemen’s Council, plans to release a million fireweed moths and larvae by the end of the year.

* Chris Sugidono can be reached at