HONOLULU — The stinging caterpillars that have been established on the Big Island and recently found on Oahu, have been found on Maui. An entomologist for the Hawaii Department of Agriculture (HDOA) on Maui has confirmed that two nettle caterpillars have been turned in by two Haiku residents over the past week. The two Haiku residents, who lived about a half mile apart, each turned in one caterpillar – the first on Friday, July 6, and the other on Tuesday, July 10.
Maui staff has surveyed the area around the residences and have not detected any other caterpillars. Pheromone traps, which attract male adult moths of the caterpillar, were also set earlier this week, and so far, no moths have been captured.
“It would seem unusual to find just a single caterpillar at two different sites,” said Neil Reimer, manager of HDOA’s Plant Pest Control Branch. “We will continue to conduct surveys around Haiku and other areas of Maui to determine the extent of the situation.”
HDOA is asking residents and nurseries, especially on Oahu and Maui, to look out for the nettle caterpillar and report suspected infestations to the State’s Toll-Free Pest Hotline,
The nettle caterpillar (Darna pallivitta) was found on the east side of the Big Island in 2001 and just last month were found at a Central Oahu nursery. Pesticide treatments continue at the Oahu nursery, as well as pheromone trapping and manual removal of nettle caterpillar cocoons.
Stings from the caterpillar may cause allergic reactions in those who are sensitive to the venom. If stung, treatment recommendations include immediately washing the affected area with soap and water to remove any residue, applying ice to reduce swelling and consulting a physician to determine if further treatment is necessary. Individuals who are sensitive to the venom should seek prompt medical attention, especially if they experience difficulty breathing or if they are stung in the eyes.
Nettle caterpillars grow to about one-inch long, white in color with black bands. The caterpillar has distinct bristly spines that when touched, may cause a burning sensation that lasts about an hour. (See attached Pest Advisory.) The adult moth is slightly smaller than a dime and is triangular in shape. It is bicolored with the front 2/3 of the body a yellowish-brown and the posterior 1/3 is brownish. The adult flies at night and hides under leaves during the day. The caterpillar has been found primarily on the underside of the leaves of palm plants, grasses and lilies.
After the discovery of the nettle caterpillar in Hilo, HDOA began research on potential biological control agents – natural enemies of the nettle caterpillar that specifically attack this pest without harming native or other beneficial insects and the environment. An apparent parasitic insect of nettle caterpillars was found in Taiwan and has undergone testing in HDOA’s Insect Quarantine Facility in Honolulu. HDOA is currently in the process of obtaining approval from federal and state regulatory entities to release the biocontrol insect. This process is expected to take about another six months.
Chemical control of the pest include insecticides routinely recommended for use to control leaf-feeding caterpillars include carbaryl and acephate. For those who prefer to use a non-toxic pesticide, Bt (Bacillus thuringiensis) sprays have proven to be effective against the larvae of various moths, including the nettle caterpillar. Bt is not toxic to humans, other animals, and the environment. All pesticides should be used according to label instructions.