Posted on: Tuesday, April 1, 2003

Efforts to eradicate weed go well on Big Island

By Kevin Dayton
Advertiser Big Island Bureau

HILO, Hawai'i — Conservationists believe they have scored at least one victory in the fight against Salvinia molesta, the noxious weed that has been choking Lake Wilson. While crews are still working to clear the lake on O'ahu, herbicide spraying has almost wiped out much smaller patches of the plant in Hilo's Waiakea Fish Pond.

Robert Nishimoto, aquatic biologist for the state DLNR aquatic resources division, said he believes there is still some salvinia growth in the pond, but herbicide spraying in January and February seems to have controlled it.

The weed was mostly growing among the California grass along a bank of the 26-acre pond near where it connects with Hilo Bay. Nishimoto theorizes that the salt and the turbulence of the water with the rise and fall of the tide helped keep the growth of Salvinia in check. Patches were also found near the Wailoa Center.

"Somebody probably let it go or somebody got tired of it and threw it away," Nishimoto said. "It doesn't take much for these things to take off, you know."

Nishimoto would know. One of his first jobs after arriving in Hilo in the early 1980s was to clear thick water hyacinth that had nearly taken over the pond. He initially took on the job himself, although he later got help from other agencies.

When word came late last year that the new pest was moving in, "we blasted it," Nishimoto said. The DLNR aquatic resources and parks division contributed workers for the effort, while the Department of Agriculture provided spraying equipment and the Department of Health monitored the project, Nishimoto said.

Wayne Okamura, a Kohala fish farmer, spotted the weed in Waiakea Pond when he stopped there to collect samples of tilapia.

"It's a really easy weed to identify," Okamura said. "If someone's out there watching, then they can keep things a little bit cleaner. During the past 20 years, I've seen pristine areas just get taken over."

Nishimoto said workers will watch for any more patches of the weed, and is encouraging the fishermen to keep an eye out for it.

At Lake Wilson, state officials have pulled out more than 26,000 cubic yards of the weed, but said last week they believe they have cleared less than one-third of the 300-acre reservoir.