Hi'iaka's Healing Herb Garden

Please note: this version of my column may differ from the one published in Hawaii Island Journal due to editorial changes, particularly those having to do with length.

Painful Caterpillar Lurks in Palms and Grasses

I’ve been stung. A friend was stung while walking past some areca palms on my property. Maybe they have stung you too.

What are they? The stinging nettle caterpillar is one of many recent invasive species introductions to our island. The Darna pallivitta is “of major concern,” according to the University of Hawai‘i Cooperative Extension Service, because of its “painful sting, voracious appetite, lengthy larval stage… high fecundity (480 eggs per female), and wide host range. A heavy infestation can defoliate a potted plant in just a few days.” Covered with spiny hairs, this small caterpillar grows to only about one inch in length, has a dark stripe down its back and light-colored venomous spines and hairs. (hear.org) These hairs release a painful irritant when your body is unfortunate enough to make contact with them. So be careful when you are around palms, ti leaves, grasses and lilies, because these are some of the plants this caterpillar just loves to eat and live on.

Darna pallivitta. Photo courtesy of
Hawai‘i State Department of Agriculture.

First discovered in 2001 near Pana‘ewa, just south of Hilo, this creature comes from Taiwan, China, Thailand, Malaysia and Indonesia. Currently, it exists mainly on the Big Island, but was discovered on O‘ahu in June of this year, and more recently, on Maui in July. A September 2005 news release from the Hawai‘i Department of Agriculture (HDOA) reports, “stinging incidents are increasing on the east side of the Big Island as infestations of the caterpillar expand.”

Treating a sting

Different people react differently to this caterpillar’s sting: a red welt can pop up and the area might swell quite a bit. The itching of my stings was extremely unpleasant and lasted four days. I also had a fair amount of swelling. A brochure from the Cooperative Extension gives these instructions for treating a sting:

•    As soon as you realize you’ve been stung, move away from the plant and the area where it happened (don’t do what I did, continuing to prune my arecas and getting several more stings in the process).

•    Wash the affected area immediately with soap and water and apply ice to reduce swelling.

•    If you are so inclined, you can take an oral antihistamine such as Benadryl, which can help relieve the itching and swelling.

•    Hydrocortisone cream can also help the symptoms.

•    As with any medical emergency, seek medical attention if you have trouble breathing or if it stings your eye.

Herbal helpers include comfrey and plantain (lau kahi), aloe vera, and tea tree oil, which helped me greatly (but only temporarily). If you use essential oil, mix it with a “carrier” oil or lotion to dilute its very strong effects.

A poultice is plant material that you apply to your skin to help heal a wound, bite, burn or other skin ailment such as this caterpillar’s sting. A comfrey poultice is easy to make:

Brew a “decoction,” which is strong tea. Boil 2 cups of water in a non-metallic pan such as Pyrex. Chop 1 cup of fresh comfrey leaves and/or root, or use about one-half cup of dried plant material. Reduce the heat to a simmer and then cook for 20 minutes. Allow it to cool before you apply it.

Then take your “goo” and apply it to your sting. I sometimes use adhesive tape to hold it in place, because the longer you leave it on, the more effective it will be. You can leave it for several hours or overnight, and then re-apply a fresh wad the following day if you feel it is necessary.

Controlling it

A June 7, 2007 press release from the Hawaii State Department of Agriculture says chemical insecticides such as carbaryl and acephate are effective. However, there is a safer, non-toxic alternative: Bt (Bacillus thuringiensis) sprays are effective against certain caterpillars, including this one. Bt is not toxic to humans, other animals, or the environment.

Scientists from the U.S. Department of Agriculture have created a synthetic scent imitating the nettle caterpillar female. It attracts males and may be used to monitor infestations on Hawai‘i Island and to locate caterpillars throughout the state. Statewide efforts include containment efforts on O‘ahu, new pest advisories, news coverage, and outreach materials that help educate the public about this invasive species.

You can help

Preventing the spread of this and other pests between the islands is very difficult. The State Department of Agriculture asks all of us, and especially nurseries, to report sightings of this caterpillar to their Pest Hotline at 643-PEST (643-7378).

On the Web:
hear.org/species/darna_pallivitta/
hawaiiag.org/hdoa/newsrelease/05-19.htm
esa.confex.com/esa/2005/techprogram/paper_21379.htm
hawaii.gov/hdoa/meetings_reports/news-releases/2007-news-releases/news-release-nr07-14-july-13-2007
hawaii.gov/hdoa/meetings_reports/news-releases/2007-news-releases/news-release-nr07-12-june-7-2007/
pbin.nbii.gov/reportapest/maui/pestlist/darpal.htm

=============================================================
Barbara Fahs is the owner and creator of Hi`iaka's Healing Herb Garden, LLC and author of the book Super Simple Guide to Creating Hawaiian Gardens. Contact her at 966-6126 or www.hiiakas.com to learn about her workshops, internships and Garden tours.