The stinging nettle caterpillar (SNC) was first discovered on the Big Island in September 2001. In addition to eating holes in some favorite ornamentals, SNC could leave burning welts on exposed skin, such as that on arms and legs.
The stinging nettle caterpillar (SNC) was first discovered on the Big Island in September 2001. In addition to eating holes in some favorite ornamentals, SNC could leave burning welts on exposed skin, such as that on arms and legs.
Now, 13 years later, there is relief.
At a nursery in Taiwan, in October 2004, a tiny wasp was found that attacks the larvae of the SNC. These small parasites were collected and brought back to Hawaii. In subsequent tests, they were shown to be highly specific to the SNC and would not pose a threat to nontarget organisms.
State and federal regulatory agencies, therefore, approved the release of this parasite in the state of Hawaii.
Periodic inspections were made of the release sites. After 12 months, the parasite was successfully established and had sufficiently suppressed the stinging nettle larvae by more than 80 percent. Counts of the adult moths trapped in pheromone traps also were significantly lower.
Subsequent field surveys suggest the parasite is established throughout the islands and is keeping the stinging nettle caterpillar in check.
For those not familiar with this pest, here is a brief description:
• The SNC has a voracious appetite for many plants in the garden including palms, dracaena, ti, coffee, gardenia, banana, California grass, mondo grass, guava, macadamia, monstera and red and shampoo gingers. 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 its back. The adult moth is about 1/2 inch long, with a rust to light brown coloration.
Control: Optimistically, no treatment will be necessary as the parasitic wasp spreads.
Should treatment be necessary, here are some control measures:
1. 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.
2. There are a number of insecticides that are effective against the larval stage. One of the safer ones is Bacillus thuringiensis (BT), also known as Dipel. Considered organic, BT is a bacterium that 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 might stop itching and swelling.
• Hydrocortisone creams might 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.
You also can check out the CTAHR website at www.ctahr.hawaii.edu for an informational brochure.
Aloha, Nick. As a seed saver, I usually limit my veggies to heirlooms, but your article about oriental green zen was so interesting that I decided to try it. However, you neglected to tell your readers what seed company or store sells it. Mahalo, Rene
There could be other companies that sell the zen seeds, but Burpee seed company is the main one. Go to www.burpee.com and search under oriental greens, zen hybrid.
Coffee pamphlet
UH CTAHR recently published a pamphlet, “The Economics of Coffee Production in Hawaii.” It can be accessed online at www.ctahr.hawaii.edu/oc/freepubs/pdf/EI-25.pdf.
The typical Hawaiian coffee farm is a family operation with less than 2 acres of land. Farms with revenues less than $10,000 a year make up the majority of farms. When considering all coffee farms, the majority are profitable and efficient. Taxes and interest make up the largest percentage of costs for noncommercial farms; labor is the largest portion for all other farms.
I want to encourage HTH readers to stay informed with factual information pertaining to a variety of gardening topics. Check out more than 230 entries on my website at gardenguyhawaii.com.
Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegarden guy@earthlink.net. You also can visit his website at www.gardenguyhawaii.com.