The U.S. Department of Agriculture's approval of using moth caterpillars from Madagascar in the battle against fireweed was welcomed Wednesday as a long-awaited, effective weapon to kill the noxious weed that sickens and sometimes kills cattle.
"This is fantastic news," said Lissa Fox Strohecker, public relations and education specialist with the Maui Invasive Species Committee. "I know many farmers and ranchers have been hopeful that the Hawaii Department of Agriculture might be able to find a biological control suitable for release."
U.S. Sen. Daniel Inouye announced Wednesday that the state Department of Agriculture had received approval from the USDA's Animal and Plant Health Inspection Service to release the Arctiidae moth to combat fireweed, also a native of Madagascar.
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While a single fireweed flower appears harmless, it is toxic to cattle. A single plant produces 30,000 seeds annually that are dispersed by wind, hiking boots, vehicles and animals. The weed can quickly spread over an entire pasture, which has happened on at least 70,000 acres on Maui, mostly Upcountry. Now, the U.S. Department of Agriculture has approved releasing a species of moth that, in its caterpillar stage, defoliates and kills the fireweed.
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The weed covers at least 70,000 acres on Maui, primary Upcountry, "but it's spreading throughout the island as well as on Lanai and has been found on Molokai," Strohecker said. "The introduction of a natural predator, or biocontrol, could check the spread of this pest and provide a long-term, sustainable and cost-effective solution. Without control, fireweed destroys pastureland and the release of the Arctiidae moth could mean significant savings for our ranchers and farmers struggling to control fireweed."
Fireweed has infected an estimated 850,000 acres on Maui and the Big Island, according to Inouye. The drought-resistant weed has no natural predators in Hawaii, and each plant produces 30,000 seeds annually that are spread by wind, hiking boots, vehicles and animals.
James Leary, an invasive weed management specialist with the University of Hawaii's College of Tropical Agriculture and Human Resources, said fireweed makes cattle sick because it has a toxic pyrrolizidine alkaloid. Cattle that eat fireweed can suffer liver damage, have a lower birth rate and, in acute cases, die.
The result for Hawaii ranches is lower herd sizes and lower profits, he said.
Fireweed has been a tough foe for invasive weed specialists because it is "highly adapted to Hawaii's environment," Leary said.
The weed competes with foraging grasses cattle need for food, and, because it's resistant to drought, it's more able to thrive when there is some rain in the drought that has plagued Maui and the Big Island, he said.
"What we're seeing is that with any kind of rainfall, fireweed comes back faster than grass," he said.
The moth caterpillars eat the fireweed's leaves, eventually defoliating the entire plant, Leary said.
The caterpillars performed well in a controlled, confined condition for experiments, he said.
"We don't know how it will perform in the natural environment," he said.
The next phase will be the release of the moth into the environment and then monitoring its impact on fireweed and other plants, especially native plants, Leary said.
In the next month or two, the battle against fireweed will shift to a phase in which efforts will focus on building up a population of the moths for release, he said. Eradication efforts will be limited by the number of insects available.
The specific species of moth was captured by exploratory entomologists in Madagascar in 1999. So, it's taken 13 years of research to reach the point where the moth can be released, he pointed out. "That's how much effort goes into preparing a biocontrol," he said.
Leary said fireweed is a bigger problem on the Big Island, particularly in Waimea and Kohala, where drought has been more severe and there's more pastureland for the weed to spread.
The weed is so hardy that it has been found at the 13,000-foot summit of Mauna Kea, he said, and it has occasionally cropped up in Haleakala National Park. On Maui, the weed has been seen below the 1,000-foot elevation in Haiku, he added.
From 2010 to part of 2011, Maui County sponsored a $100,000-per-year fireweed management program to provide ranchers with herbicide to control fireweed, but it turned out to be only a temporary solution.
Teena Rasmussen, director of the county Office of Economic Development, said the herbicide program was not effective, and the county shifted its efforts this fiscal year to supporting the less-expensive moth biocontrol program.
The county set aside $25,000 for biocontrol efforts on fireweed, she said, adding that her office has been working with Leary on a protocol for release of the moth when its use was approved by the USDA.
"We're very happy the Department of Agriculture made this decision," Rasmussen said. "It should help the ranchers enormously. They don't like spraying herbicides on their pastures. It's very expensive and time-consuming. It's very good news for everyone."
* Brian Perry can be reached at bperry@mauinews.com.
