Question: Whatever happened to the project to control the infestation of nettle caterpillars in various parts of Hawaii?
Answer: Entomologists are regularly monitoring the infestation through experimental sites set up across the state to observe the effects stingless wasps, the biological agent, have on nettle caterpillars.
Sites were set up in Waimanalo and Kipapa Gulch on Oahu and the Maliko Gulch in Maui. Sites also were set up near Kurtistown and Umauma on Hawaii island.
The state Department of Agriculture’s Plant Pest Control Branch began the project more than a year ago to eliminate the infestation that was killing plants.
During a 12-month period, experts observed an 80 percent decline of the prickly pests at the sites after the introduction of the parasitic wasp, according to Renato Bautista, entomologist and insectary supervisor at the Plant Pest Control Branch.
An experimental site was not set up in Kauai, but wasps were released in Kapaa and Waialua in October 2010 after the caterpillars were detected at private homes and nurseries.
Some residential areas in Mililani, Waimanalo, Hilo and Maui also were affected by the pests.
The nettle caterpillars, or Darna pallivitta, were first discovered on rhapis palms at a Panaewa nursery on the Big Island in September 2001.
The insect grows up to an inch long and is covered with stinging spines. It’s known to attack coconut leaves, ti leaves, areca palms and other plants, causing financial loss to nurseries and presenting a hazard to workers who could suffer from welts, rashes and blisters if stung.
In 2004, the wasps were brought in from Taiwan to deal with the caterpillars. To kill the caterpillars, the wasp or Aroplectrus dimerus lay eggs on the caterpillar. Its larvae then eat the caterpillar.
Bautista described areas in Waimanalo and Kipapa on Oahu as the worst areas of infestation before they launched the project. About 40,000 to 50,000 caterpillars were seen on areca palms at a Waimanalo nursery. In Kipapa, about 26,000 to 30,000 caterpillars infested guinea grass.
To date, experts have released about 12,000 wasps at the experimental sites as well as in some residential areas. While the wasps will not completely eradicate the caterpillars, they will keep the population in check, Bautista said.
Patrick Conant, entomologist of the Plant Pest Control Branch for Hawaii island, said the number of complaints on the pests have dropped possibly due to the parasitic wasps.
Experts will determine the effects of the stingless wasps on the caterpillars in three to four years.
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This update was written by Rosemarie Bernardo. Suggest a topic for “Whatever Happened To …” by writing Honolulu Star-Advertiser, 500 Ala Moana Blvd., Suite 7-210, Honolulu 96813; call 529-4747; or email cityeditors@staradvertiser.com.
