10,000-plus fireweed eaters set free on Maui

Diana Crow, a horticulturist at Ulupalakua Ranch, has helped release more than 10,000 Madagascan fireweed moths and larvae over the past year on Maui to combat a toxic plant overwhelming island pastures.

A state Department of Agriculture official, however, said biocontrol efforts could take a decade before residents begin to notice.

In March 2013, the Agriculture Department distributed more than 2,500 moths and larvae to farmers and ranchers so they may rear the insects on their properties to continually devour the fireweed. Crow was one of the recipients.

“It’s a daily thing, especially when there are thousands of eggs hatching,” she said Wednesday. “They (larvae) are so tiny and when I open the door to feed them they’re everywhere. I herd them with a paintbrush because they’re so tiny they only have so much energy and need to find food right away.

“Once they get bigger, though, it’s easier; it’s just throwing food in there until they pupate (or cocoon) and emerge as moths.”

Crow has been cultivating the moths in four steel cages about 2 feet high by 1 foot long and wide, inside a plant nursery at the ranch. In the beginning, she used only a couple of the cages out of fear of disease spreading among moths but now uses all four.

“When we first started, we didn’t really know what to expect, but then realized they’re a lot more hardier than we thought,” she said. “We are seeing them out in the field but not in the concentrations we need.

“I wanted to see results faster.”

Mach Fukada, a state entomologist and biological control specialist, cautions that the benefits of “weed biological projects could take 10 years before we see any appreciable results.”

“Right now, I’d say it’s a little premature,” Fukada said Wednesday. “But I do see evidence of caterpillars and adult moths spreading very easily, and if everything’s working out as it should and they get established – then we’ll see what happens.”

When ranchers and farmers received their batches of moths and larvae early last year, Fukada helped educate them on how to properly care for the insects. Since then, he has focused on recording sightings of the moths and larvae on a map of Maui – asking farmers and ranchers to send him photos of their locations.

“Right now what I’ve looked at is how far and wide the moths have dispersed as an indicator of how well it’s able to get around without people intervention,” he said.

Fukada said populations in Ulupalakua, for example, are “well established” so he is focusing on surrounding areas such as Pukalani, Makawao and Haiku. He added that distant areas like Kahoolawe, which has a “well-known and established fireweed” problem due to wind carrying seeds to the island, has recorded sightings of larvae as well.

“One morning I found one adult in Kahului at (University of Hawaii Maui College) so maybe it didn’t fly there but hitched a ride by car or student,” he said. “If that’s the case, it has a good way of getting around.”

Fukada monitors the spread of the moths and larvae, in addition to his other duties, by driving around well-lit areas that might attract moths to make it easier to identify them. He said his real work, though, will begin if, or when, the moth establishes itself on the island so he may monitor its overall effectiveness.

“We’ll never get to the point where we see eradication; there will always be fireweed,” he said. “That’s the most important thing that people need to understand.”

Crow plans to release her next batch of fireweed moths and larvae in a couple of weeks and is giving “a bunch” more to Kaupo Ranch.

“Somebody in my position, who can attend to them (insects) – some of the other ranches don’t have that situation,” she said, adding that she has given some to Haleakala Ranch as well. “But we’re all in this together so we help each other.”

Gerard Thompson, owner of Thompson Ranch in Kula, was among the ranchers who received the first batch of moths and larvae early last year. However, weather and wind caused his stable of insects to be blown away.

“I had set a little bit out and they were propagating and getting some hatchings,” he said. “Then the screen box blew over and that was it. I don’t really see them around now.”

Thompson, who owns around 1,400 acres, raises Angus cattle and meat goats, as well as offering horseback riding tours. He said the proliferation of fireweed lowers the quality of feed on his land for his animals to eat.

“I got a few areas with fireweed problems due to the drought, but with the rain a little more fireweed is coming in,” he said.

Although the fireweed remains a problem on his ranch, he hopes the recent surge in rain and future warm weather will help “choke out” the rest of the fireweed.

“I hope it continues to rain for a couple more weeks because now’s a good time for us because the weather’s warmer and it really helps the feed grow,” he said.

* Chris Sugidono can be reached at csugidono@mauinews.com.