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BIISC focusing on eradication of devil weed

Hawaii County residents are urged to be on the lookout for an highly invasive plant found on the island this year that could devastate the cattle industry.

Chromolaena odorata, also called the “devil weed,” was first detected on Oahu in 2011. Until this year, it was never able to cross over to the Big Island, but early this year it was found near the Hilo motocross track behind the Hilo landfill, with subsequent surveys finding more weeds gaining footholds in Puna in Leilani Estates and Hawaiian Paradise Park.

Franny Brewer, spokeswoman for the Big Island Invasive Species Council, said devil weed has particularly small and sticky seeds, which makes it easy to spread unknowingly. These small seeds likely hitched a ride to the Big Island on the equipment of users of the Kahuku Training Area and Kahuku Motocross Track on Oahu, where the plant was first found in Hawaii.

“Right now, we’re actually lucky that it’s just on the east side of the island,” Brewer said. “It usually likes the warmer and drier areas, so if it gets over (to the west side) that could be very bad.”

Brewer said BIISC is prioritizing the control and eradication of devil weed before it can spread any further. Although devil weed is carcinogenic to humans if eaten, it is, more importantly, also toxic to cattle. And because of the presence of the invasive two-lined spittlebug among Big Island pastures, both species could deliver a one-two punch to the island’s ranchers.

The spittlebug is attracted to the same nitrogen-rich grasses that are preferred by cattle for grazing, Brewer said, and can reduce entire pastures to dust. A recently devastated pasture in West Hawaii would be the perfect foothold for devil weed to take over and thrive.

Furthermore, the same substance in the weed’s leaves that makes them unappetizing for herbivores also makes them particularly flammable, Brewer said, which would literally add fuel to the increasing number of wildfires on the island in recent years.

Brewer said wildlife management groups on Oahu tried in vain to rein in the weed for a decade, only to finally conclude that the plant is, at this point, ineradicable on the island. BIISC hopes that early public engagement will be able to control the plant on the Big Island before it reaches the same point.

“We’re asking people to keep an eye out for weeds, bugs, anything you’ve never seen before,” Brewer said, adding that members of the public should take pictures of plants they think might be devil weed, but not attempt to remove the weed themselves, in order to avoid inadvertently spreading its seeds.

Unfortunately, devil weed also can be hard for the layman to identify, being a generally innocuous-looking plant named for and identifiable by a vaguely pitchfork-shaped pattern on its spear-shaped leaves. It can, but does not always, have nondescript small white flowers, which Brewer said does not make it particularly distinctive among other plants.

Brewer said BIISC will investigate suspected weeds and remove them free of charge, and will also inform neighbors when the weed has been detected in the area.

In the future, Brewer said BIISC hopes to train dogs to detect the plants, which will allow BIISC to find them more efficiently than with just human eyes.

Meanwhile, the state Legislature this year awarded the state Department of Agriculture $350,000 to help control the two-lined spittlebug. Brewer said much of the strategy for dealing with the spittlebug is based around experimenting with other grass species that can resist the bug but can still survive on the island.

“Most of these grasses are from Brazil, because they’ve been dealing with the spittlebug already,” Brewer said. “The bugs have really hit the kikuyu grass here really hard. … Unfortunately, that grass supports 70% of the cattle on the island, but it will all have to be replaced at this point.”

Photos of suspected devil weed can be sent to biisc@hawaii.edu.

Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.
Source: Hawaii Tribune Herald

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