A proposal to fund measures to control a destructive invasive pest is on the verge of passing in the state Legislature.
The two-lined spittlebug is an insect whose voracious appetite for key livestock grazing grasses has made the species a menace for ranchers on the Big Island since it was first discovered here in 2016.
The insect draws its name from the frothy mass of foam secreted by its nymphs — the juvenile stage of the insect between its larval and imago form — onto nitrogen-rich grasses for the bugs’ protection. For now, the insects are confined to leeward parts of the Big Island and have not been detected on other islands.
While the nymphs don’t do too much damage to the grass as they feed, when they reach adulthood, they can devastate whole pastures, which often don’t grow back and are instead replaced by weeds — often species that also are invasive.
House Bill 2131 would allocate an unspecified amount of money — earlier drafts of the bill specified $800,000 — to the state Department of Agriculture to mitigate, control and reduce the spittlebug’s population and recover lands damaged by the species. The bill has passed third reading in both chambers and has been forwarded to conference committees.
Franny Brewer, program manager at Big Island Invasive Species Committee, said the most promising method for controlling the species is the gradual replacement of grasses with variants that are more resistant to the insect.
“Pesticides are just not feasible for dealing with an entire pasture,” Brewer said. “If it’s a lawn, then, yeah, you can spray down your lawn, but for a thousand-acre ranch, we can’t tell a rancher, ‘Sure, go to ACE Hardware and pick up some pesticides.’”
Brewer said research is still being conducted on the best grasses to resist the insects, but added that it may be harder to figure that out on the Big Island than on the mainland. She said that while mainland pastures tend to be more uniform over wide areas, Hawaii Island’s climate can change drastically over fairly small distances, so finding a grass species that is suitable for all zones might be impossible.
Other methods of managing the bug are still expensive or require rapid and coordinated efforts, said Mark Thorne, pasture and livestock management specialist for the University of Hawaii at Manoa’s Tropical Pasture &Livestock Management Academy.
Currently, the best known strategy for managing the insects from a pasture involves a fair amount of timing, Thorne said. If a rancher can catch the nymphs early enough, a session of intensive grazing in the same area can cut down on the population significantly.
“You hit the nymph population with the grazing pressure,” Thorne said. “Then, that exposes the spittle to the warmer air, which dries them out, (and then) they’re vulnerable to birds that can eat them, (and also) maybe the greater hoof action kills some of them that way.”
Thorne said pesticides are too unreliable to deal with the spittlebugs. Because the nymphs tend to place their spittle masses low on the grass stalk, contact pesticides often won’t reach the bugs at all. At the same time, he added, wide use of pesticides can also kill potentially beneficial insects.
However, Thorne said that there has been a silver lining to the persistent drought conditions that have plagued the island: The dry conditions have limited the spread of the spittlebug’s range.
“It’s hard to say what sort of (bug) season we’ll have this year,” Thorne said. “It depends on what sort of weather we’ll see this spring, but we’re in this shifting weather pattern between El Nino and La Nina, and we don’t really know what’s going to happen.”
The insects enter a dormant state, called diapause, in winter and typically begin to emerge right about this time of year, Thorne.
Brewer advised residents to be aware of any dead patches of grass on their lawns or properties and check the area for any masses of spittle near or on the soil line. If suspected two-lined spittlebugs are detected — particularly if they are outside the Kailua-Kona area — the resident should contact BIISC.
More resources for how to identify and manage the spittlebug can be found at rangelandsgateway.org/twolined-spittlebug.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.
