HONOLULU — The stinging nettle caterpillar, Darna pallivitta, which has established populations on Big Island, O‘ahu and Maui, has also been found on Kaua‘i, according to a Hawai‘i Department of Agriculture press release.
The HDOA was alerted to its presence on Kaua‘i in August 2010 by the owner of a plant nursery who recognized the caterpillar and turned it in to HDOA’s Plant Quarantine Branch.
Residents on the Garden Isle may begin to see more of the caterpillars during its peak months in the summer. HDOA is asking the public’s help in reporting possible infestations.
The inch-long, spike-covered white caterpillar with a long stripe running down its back packs a painful sting when it comes in contact with the skin. Those who are allergic may have more serious symptoms, such as difficult breathing. This caterpillar is also a plant pest which has been found feeding on more than 45 species of plants, including palms and coffee.
When the caterpillar was discovered, pheromone traps were set up at various nurseries and adult moths were found in Wailua, Kapa‘a and Kilauea. Currently, there are about 35 pheromone traps that are being monitored throughout Kaua‘i.
To help control the pest, HDOA released a natural enemy of the nettle caterpillar, a tiny wasp called Aroplectrus dimerus, which has been successful in controlling the nettle caterpillar on other islands. Releases were conducted on Kaua‘i in October 2010 and in May 2011 with more than 600 individual wasps released in all. Although it is called a wasp, it is the size of a gnat and is not harmful to humans or other animals. The tiny wasp lays its eggs on the nettle caterpillar and when the eggs hatch, the larvae feed, breed and develop on the nettle caterpillar larvae.
HDOA’s former Plant Pest Control Manager collected the wasp in Taiwan in 2004 and sent them to HDOA’s Insect Containment Facility in Honolulu where tests were conducted under quarantine conditions to determine if it would attack any other species in Hawai‘i. Testing indicated that the wasp is host specific to the nettle caterpillar and does not pose a potential threat to non-target organisms. Other predators of the nettle caterpillar were also tested in quarantine, but were rejected as candidates for release because they also attacked other beneficial and/or native insects.
Researchers are also studying other ways to combat the nettle caterpillar, including the use of a synthetic scent which imitates the scent of a female nettle caterpillar. The pheromone lure has been effective in helping to monitor infestations throughout Hawai‘i .
Kaua‘i residents, in particular nurseries, are asked to report sightings of this invasive species to the state’s toll-free Pest Hotline at 643-PEST (643-7378).