Insect could slow spread of smelly skunk vine
By Timothy Hurley
Advertiser Staff Writer
Skunk vine, maile pilau, lesser Malayan stinkwort, stink vine.
Kim and Forest Starr
From its various common names, you get the picture that Paederia foetida isn't exactly welcome in most gardens. Indeed, the malodorous vine is an uninvited guest in Hawai'i that has spread its way onto the state Department of Agriculture's Top 10 list of established weeds.
Paederia foetida, also known as the malodorous skunk vine, is naturalized in the wild on Kaua'i, O'ahu, Maui and the Big Island, but has apparently spread most on O'ahu.
But now a foreign flea beetle could play a key role in controlling skunk vine, which grows densely over trees, ornamentals and cash crops both here and in the southern United States.
State Plant Pest Control Branch scientists in Honolulu have been conducting tests to see if the beetle might serve as a control agent to fight the spread of skunk vine. The project is a collaborative effort with the federal Invasive Plant Research Laboratory in Fort Lauderdale, Fla.
Scientists with the Agricultural Research Service, the U.S. Department of Agriculture's research arm, found the flea beetle, Trachyaphthona sordida, and other possible biocontrol candidates in Japan and Nepal, where the insect helps to keep skunk vine under control in the plant's native habitat.
In summer 2002, they captured three batches of 200 flea beetles and shipped them to Hawai'i for testing to determine what plants the insects tend to feed on and to assess any potential risk from their use as biocontrols.
This flea beetle has been recorded as feeding only on skunk vine, and scientists are hopeful it will pose no risk to agriculture or native ecosystems in the United States.
Ken Teramoto, chief of the biological control section of the state Department of Agriculture, said Hawai'i officials were more than happy to cooperate with the federal project, given the tenuous nature of research money. But local officials aren't just doing the federal government a favor. He said skunk vine is bad news in Hawai'i, causing the most trouble in horticultural crops.
In Hawai'i, the species is naturalized in the wild on all four major islands, from coastal lowlands to midlevel mountain slopes. But it has apparently spread the most on O'ahu, where it was first recorded in 1854.
Teramoto said the federal scientists also sent to Hawai'i a lace bug from Japan that also attacks the vine, but here it was discovered to feed on the noni plant, a Polynesian introduction important for medicinal purposes. Those insects were destroyed, he said.
As for the flea beetle, biocontrol work is time-consuming, and it could take years before officials know if it will be safe enough to release into the environment, he said.
Skunk vine is so smelly the Japanese have nicknamed it the "human gas vine."
"You can smell it before you see it," said Forest Starr, a U.S. Geological Survey biologist who documented populations of skunk vines in a report on invasive species on Maui. While skunk vine isn't as widespread on Maui as it is on O'ahu, Starr said it would still be difficult to control on the Valley Isle. The Maui Invasive Species Committee decided not to make it a target species, he said, because it's too established to eradicate.
Reach Timothy Hurley at (808) 244-4880 or thurley@honoluluadvertiser.com.
