Tuesday, March 20, 2012

Stinging Nettle Caterpillar

                                                        Caterpillar and pupa 

The stinging nettle caterpillar (Darna pallivitta)has a voracious appetite for many plants in the garden including palms, dracaena, ti, coffee, gardenia, banana, perennial peanut, California grass, mondo grass, guava, macadamia, monstera and red and shampoo gingers. What is even more alarming is the burning and itching caused by the spiny hairs on the caterpillars.    
                                                             Adult Moth

The stinging nettle caterpillar is new to the Big Island, coming here in 2001.  It has spread throughout the East side of the Island and is currently closing in on the Kona area.  The larvae are up to 1 inch long and covered with many rows of stinging spines.  The caterpillar varies from white to light gray with a dark stripe down it‘s back. The adult moth is about ½ inch long, with a rust to light brown coloration.

Control – Since the moths are nocturnal and attracted to light, putting up a bug-zapper with an ultraviolet bulb should reduce the pest’s population. Place a bucket of soapy water underneath the trap to catch fallen moths.  This is done in case the zapper doesn’t kill them and to give an idea of how bad the situation is. The Hawai`i Department of Agriculture is working on releasing parasites for natural biological control.   

There are a number of insecticides that are effective against the larval stage.  One of the safer materials is Bacillus thuringiensis (Bt), also known as Dipel. It is a bacterium which is harmless to humans but deadly to caterpillars.

If you are stung by this caterpillar:
·        Wash the area immediately with soap and water.
·        An oral antihistamine may stop itching and swelling
·        Hydrocortisone creams may stop itching and swelling.
·        Get medical attention immediately if you experience difficulty breathing or are stung in the eye. Skin reactions vary from a red welt to severe swelling lasting a couple of days.

Check out CTAHR’s website at  www.ctahr.hawaii.edu  for pictures and a more detailed informational brochure.  

Photos by Brian Bushe