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The Honolulu Advertiser
Posted on: Wednesday, February 5, 2003

Pesky leafhoppers plague watercress crop again

By Catherine E. Toth
Advertiser Staff Writer

The pesky aster leafhopper that devastated watercress producers last year — even forcing some of them out of business — has invaded the state's largest watercress farm again, causing another shortage in the vegetable popular in Korean restaurants.

Sumida Farms, which produces about 60 percent of the state's watercress, had to remove and replant about 35 percent of its crop in the past few months after an invasion of a species of aster leafhoppers, now called watercress leafhoppers.

Last year it lost about 10 percent of its crop because of leafhoppers.

The 10-acre farm below Pearlridge Center on Kamehameha Highway lost about 21 tons of watercress, costing the company roughly $42,000.

"It got really bad in October, it still is," said David Sumida, the farm's operations manager and spokesman. "We're trying to get it under control. It's one of the worst pests I've ever seen."

Production for watercress dipped 13 percent from 2000 to 2001, the most current statistics available, said Don Martin, state agricultural statistician. But he couldn't say whether the leafhopper invasion was the reason for the decline.

Restaurants around O'ahu have felt the effect of the leafhopper invasion on Sumida's farm.

"It's not expensive; there just isn't any," said Jan Yoshimura, an administrator for Yummy Korean Bar-B-Q, which operates 11 stores on O'ahu. "No more."

Yummy uses about 150 bunches of watercress a day, more than any other Korean restaurant. It is the restaurant's most popular vegetable dish.

Hibiscus Korean BBQ in the 'Aina Haina Shopping Center has also been affected by the shortage. It uses about 10 bunches a day — and runs out after lunch.

"Demand is always greater than supply," Sumida said. "We never have enough to export."

The watercress leafhopper transmits a disease called "aster yellows," relatively new to Hawai'i but common on the Mainland, where the insect invades vegetable and flower crops. In Hawai'i, so far, the insect has attacked only watercress crops, mostly in Waiau, Waipahu and Pearl City.

According to state statistics, watercress is one of a dozen vegetable crops with more than $1 million in farm sales annually. Sumida Farms produces about 6 tons of watercress a week.

The leafhopper can be killed with malathion, the only pesticide approved for use. But the disease is the real problem.

It attacks the plant and stunts its growth. Plant leaves turn yellow. Farmers have to remove the entire plant and regrow the crops. It takes eight weeks for a watercress crop to mature.

Bernarr Kumashiro, a taxonomist with the state Department of Agriculture, said the population of watercress leafhoppers seemed to have dropped about six months ago, most likely because of farmers controlling the insect with pesticides and local parasites attacking leafhopper eggs.

"We were trying to control the disease by controlling the vector (or insect) by spraying pesticides at regular intervals," said Sumida's entomologist, John McHugh. "But in spite of the spraying, the disease seemed to be spreading. We were continuously getting new leafhoppers coming into the farm despite our best efforts to control the vector."

He discovered that a watercress farm in Pearl City near Lehua Avenue — abandoned after it was devastated by the leafhopper — had become a breeding ground for the insect. Strong Kona winds likely blew the leafhoppers into Sumida Farm. McHugh cleaned up the abandoned location, and that seems to be helping.

"For awhile there I thought we were going to go out of business," McHugh said.

"But I think we're back in business now."

Reach Catherine E. Toth at ctoth@honoluluadvertiser.com or 535-8103.