A new insect arrival is threatening West Hawaii’s pasturelands.

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A new insect arrival is threatening West Hawaii’s pasturelands.

Two ranches in Kona have suffered damage from the two-lined spittlebug since September. Extension agents at the University of Hawaii at Hilo College of Tropical Agriculture and Human Resources are now working with the state Department of Agriculture to contain the pest before it can push further north.

“If it spreads out from the Kona area and gets out into the Kohala and Waimea pastures … it could be very devastating for the cattle industry here,” said CTAHR extension agent Mark Thorne.

The spittlebug, so named because it creates “spittle masses” where nymphs mature into adults, feeds at the base of grasses and sucks fluid from the plants. Over time, this weakens the grass and can kill it.

In late February, Thorne and fellow CTAHR extension agent Glen Fukumoto, along with DOA entomologist Robert Curtiss visited one of the Kona ranches, which had about 2,000 acres worth of damaged pasture.

“The kikuyu grass was pretty much dead in most areas, with weedy types of grasses coming in,” Thorne said. “There’s virtually nothing for the cattle to graze, and it was a fairly large area.”

“There was chewing damage (as is typical of other pests), but the grass was dead,” Curtiss said. “It’s definitely surprising to see that much damage that quickly.”

“It seems to be hitting the pangola and kikuyu grass really hard,” Thorne added. “Probably 60-70 percent of cattle in our livestock industry depend on pangola and kikuyu grass.”

The two-lined spittlebug is native to the southeastern United States. It’s not known how it arrived on the Big Island.

State agriculture officials are working with the Florida Department of Agriculture to identify natural enemies of the insect.

“If they’re able to do that, we would be able to import them in to the (HDOA) quarantine,” Curtiss said. “Eventually, we would want to release a biocontrol agent if we could find them.”

Biocontrol, when a natural enemy of the pest is released to help bring down population levels, has been used successfully in Hawaii before to combat invasive species, most recently to help control gall wasp infestations of wiliwili trees. Potential predators go through a quarantine period to ensure they themselves won’t turn out to be damaging to the native ecosystem.

But Curtiss said biocontrol is a solution that likely won’t be available for some time.

“The literature from the Southeast is pretty spotty,” he said. “It’s just one of the native insects that’s part of the system there. Occasionally it becomes a pest … with turf grass.”

It’s possible the spittlebug has been on the Big Island longer, Thorne said, but wasn’t noticed because damage resembled drought conditions, or because the bug was affecting golf courses, which already have pest control regimens in place.

“Once it starts working up into the pastures, the conditions change and maybe the population gets a little larger,” he said. “When ranchers see that the grass is dying that their cattle are supposed to be eating … they pay a little more attention to those things.”

Curtiss said the DOA was committed to spending some of its departmental money to fight the spittlebug and create education and outreach materials, but wasn’t yet sure of a funding amount or a timeline.

“We’re kind of starting at ground zero with our knowledge,” he said. “One of the things we’re hoping to be able to get funded is some research into general biology and ecology.”

Part of the funding will also cover more intensive surveys to determine how far the spittlebug has spread.

Because it lives at the base of grasses, “it’s a very difficult insect to find,” Curtiss said. “I actually describe it as being cryptic.”

CTAHR and the DOA are hoping to find some sort of effective pesticide that can be used on pastures.

“Insecticides seem to be only marginally useful,” Thorne said. “And those are very expensive options.”

As of right now, he said, the best solution available is limited high-intensity grazing in areas where the bug has been spotted. This reduces the grass cover, which causes spittle masses to dry up.

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Curtiss encouraged anyone who suspects that the pest might be present in a pasture can call the DOA pest hotline at 643-PEST.

Email Ivy Ashe at iashe@hawaiitribune-herald.com.