Rearing station set up in fireweed battle

In the ongoing battle against thousands of acres infested with Madagascan fireweed, Maui ranchers will be able to pick up buckets of moth larvae to feast on the problem this summer, said officials from University of Hawaii’s College of Tropical Agriculture and Human Resources.

“We have a rearing station established in Kula where we’re currently trying to get the population large enough to distribute larvae out to the ranching community,” said Mark Thorne, a college state range and livestock specialist. “We have an anticipated larvae dispersal date sometime in July of 2013.”

Founded last month in Kula, the Maui Agricultural Experiment Station will distribute larvae based on requests to the college. Although the service is open to the public, priority will be given to ranchers and those who have the largest infected areas.

At distribution time, Thorne, whose office is in Waimea on the Big Island, will coordinate with officials at the Kula station and notify those who have larvae ready for them. Additionally, all participants must have field cages already prepared.

About 50 to 100 larvae will be inside each bucket, and the college has advised ranchers to place the larvae in heavily infected areas.

Currently, the Kula station has about eight cages, but hopes to add six more over the next few weeks, Thorne said. He hopes to have each of the cages filled with larvae by July.

“When we get an egg hatch, we could have over 1,000 larvae in a cage,” he said. “When we get the populations up to fill the cages, we’ll start pulling the larvae for distribution and keep the cages down to 100 each so they keep repopulating.

“It’s important to keep the populations down to avoid disease and overcrowding.”

While the Mealani Experiment Station on the Big Island, which Thorne also oversees, has 14 cages and has released about 2,500 larvae, he said he wants to avoid releasing too many at once and hopes to have a “running total that make this a continuous process.”

Some Maui ranches, including Haleakala Ranch and Ulupalakua Ranch, have created their own rearing operations in hopes of slowing the fireweed problem that has compounded the growing problem of axis deer.

Greg Friel, livestock manager at Haleakala Ranch, said he has three cages and recently released a couple hundred larvae on the ranch’s nearly 30,000 acres. Another 200, which have not reached the adult stage, are planned to be released soon.

Although Friel has not seen a noticeable improvement in clearing the invasive plant, he said he is confident the biocontrol measure will work, and that nearby neighbors also suffering from the plant will benefit from their distributions.

“It’s going to take a few years, but it’ll work,” he said. “It’ll just take time.”

In December, the Madagascan fireweed moth was approved by the United States Department of Agriculture as a biocontrol mechanism to slow the spread of fireweed on Maui and the Big Island. The drought-resistant plant that is toxic to cattle and horses has infested about 850,000 acres on the two islands and has no natural predators in the state.

After 13 years of research, the department and the Institute of Pacific Islands Forestry found the moth to be the most cost-effective method to combat the problem. Researchers also discovered the moth could only survive off of fireweed, and would not eat indigenous plants found in Hawaii.

With the establishment of the rearing stations on Maui and the Big Island, the department has refocused its efforts on researching the moth, rather than rearing operations, Thorne said.

For those interested in participating in the field release program, call (808) 887-6183 or send email to

For weekly updates on fireweed moth availability, go online to

* Chris Sugidono can be reached at