New Invasive Pest Threatens Big Island Range Lands, Watersheds

Two-lined spittlebug. PC: BIISC

A relatively new invasive pest is terrorizing Big Island pastures and moving disturbingly quickly up the Kohala Coast.

The two-lined spittlebug, first identified in South Kona in 2016, attacks most types of grasses. Some of those grasses are crucial to agriculture on the Big Island, including Kikuyu and Pangola grass pastures — 2,000 acres of which the pest has damaged or killed off in the Kona District of West Hawai‘i. The pastures are a vital food source for local cattle, making the spittlebug a threat to the ranching industry islandwide.

“The pest is spreading at an alarming rate, and we are all very concerned about the ranching industry on the Big Island,” said Franny Kinslow Brewer, communications director for the Big Island Invasive Species Committee (BIISC). “In three years, it has moved all the way up the Kona coast from the Captain Cook area to Pu‘u Wa‘a Wa‘a. It hits pretty much all grasses … so it is turning up in lawns as well.”

“Mainly, it is a huge threat to the grass-fed beef industry here,” she continued. “I’ve personally seen the hundreds of acres of lost pasture, now turned to invasive brush, and it’s a bad situation out there.”

The grasses in question have also been important ground covers on coffee farms and homesteads, BIISC said. The loss of them allows for the rapid increase in invasive weeds such as toxic fireweed, thorny blackberry, and other non-edible, invasive plants.

The two-lined spittlebug is also damaging Big Island watersheds and increases soil loss along with runoff into nearshore coastal waters, a significant stressor of coral health.

While this pest is only found in West Hawai‘i currently, BIISC said it is a serious threat to landscapes in other parts of the state, and it may find its way to those areas sooner than later.

Monthly pasture surveys that began in November 2017 have revealed that the pest has rapidly expanded its range. As of October of 2019, it infests over 222 square miles — or about 142,468 acres — from Pu‘u Wa‘a Wa‘a to Ho‘okena. Researchers at the University of Hawai‘i estimate that the pest is spreading its range by about 35,000 acres per year.

Two-lined spittlebug. PC: BIISC

June through September are the peak months for the invasive species. BIISC is asking the public to report any sightings of the two-lined spittlebug and to refrain from moving sod, soil, or potted plants from Kona to other areas. During peak months, adult bugs can be easily transported by plant and soil materials or relevant equipment. Cleaning off work boots before leaving one area for another is also recommended.

Two-lined spittlebug adults can be identified by the signature two red lines that go across their wings. Immature bugs, or nymphs, are found in spittle masses feeding on the roots of grass plants at the ground surface, BIISC said in a release. The nymph has a brownish head and a yellow body with faint orange/red lines on each side of its abdomen.

However, it’s the adult spittlebug that causes the most harm to grasses. The damage begins to appear in mid-summer as adults emerge and feed on the grasses causing them to turn yellow and die, which looks very similar to die back from herbicide applications.

If a member of the public finds a two-lined spittlebug adult or nymph, BIISC asks they take a picture and upload it online, or use the 643-PEST app.