Citrus-killing blackfly meets its tiny match

The bad news is that the citrus blackfly is eating away at part of Kaua’i’s

agriculture. The good news is that the damage isn’t too bad.


encouraging, officials say, is the man-induced battle with the blackfly that

two types of tiny wasps are winning.

The wasps – known formally in the

entomology world as Arnitus hesperidum and Encarsia opulenta – were introduced

on Kaua’i a few months ago by the state Department of Agriculture to attack the

blackflies, their natural enemy.

While victory can’t be declared yet on

Kaua’i, the wasps have proven on O’ahu and in parts of the mainland United

States and in Central America to be an effective way of reducing blackfly


“It takes a year or two to get (blackfly populations) under

control,” said Ken Teramoto, the Department of Agriculture’s biocontrol section

chief for plant control. “But when they’re brought to lower numbers, the wasps

can keep them manageable.”

The citrus blackfly, which actually is one of

the 30 known species of white flies, injure citrus plants by sucking out the

sap and nutrients. Feeding by large numbers of the flies can weaken trees and

reduce their fruit yields.

The blackfly was first found in Hawaii on O’ahu

in 1996. It spread from there to Maui, the Big Island and then Kaua’i.

Statewide, the heaviest infestations have occurred on pummelo (jabon), lemon,

lime, orange and tangerine trees.

On Kaua’i, the worst case was at a farm

in Kilauea. Puhi also was hit, mostly in non-commercial, backyard settings,

Teramoto said.

Juvenile blackflies appear as tiny black scales attached to

the underside of leaves.

Kaua’i ranks behind other Hawaiian islands in

commercial citrus fruit farming. Citrus was a small part of the $2.3 million in

fruit sales by Kaua’i farmers in 1998, the most recent year for which state

statistics are available.

The wasps that are taking on the blackflies are

bred and released in groups of about 200. They don’t hurt plants or humans –

they have no venom or stingers – and they’re microscopic, about the size of a

pencil point.

“You wouldn’t even know they’re there,” Teramoto


They’re small but mighty to the blackfly.

“They’re on Earth to

keep the blackflies under control,” Teramoto said.

The citrus blackfly is

a native of India. It started getting around in 1913, spreading to Jamaica, the

West Indies and eventually the Americas, including Florida and Texas, where the

bug has existed since the 1970s.

Editor Pat Jenkins can be reached at

245-3681 or


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