An inch-long caterpillar with bristly spines that deliver a nasty sting when touched has made its way to O'ahu.

The nettle caterpillar (Darna pallivitta) was first sighted at a Hilo nursery in September 2001 and had spread along the eastern side of the Big Island.

But until a week ago, the infestation had not affected other islands, state agriculture officials said.

Last Friday, a Central O'ahu nursery reported that its workers were being stung while moving plants from one site to another. State agriculture personnel surveyed the nursery Monday and found that the first site was infested with the insects.

The name of the nursery was not disclosed.

No nettle caterpillars were found at the second site but bait stations were set up in both places.

Like the Erythrina gall wasp, which has destroyed more than 1,000 native wiliwili trees in Honolulu since 2004, the nettle caterpillar is believed to have hitchhiked to Hawai'i in plant shipments from Taiwan.

Stings from the caterpillar may cause allergic reactions. Officials suggest that people who are stung wash the affected area with soap to remove residue, apply ice to reduce swelling and see a doctor to determine if further treatment is needed.

The nettle caterpillar is about an inch long with bristly spines and has white and black bands. It transforms into a nocturnal moth that is smaller than a dime and does not sting.

The caterpillar is found on the underside of palm leaves, grasses and lilies.

A predatory insect found in Taiwan could serve as a control on the caterpillar. The state Department of Agriculture is seeking approval from federal and state regulatory agencies to release that biocontrol insect, which officials believe would not present a threat to other beneficial insects and the environment, said state agriculture spokeswoman Janelle Saneishi.

The approval process takes about six months, said Saneishi.

Reach Rod Ohira at rohira@honoluluadvertiser.com.