Saturday, December 15, 2007

O Christmas Tree…and Yellow Jackets

When I lived on the mainland for a while, I once took my family camping at Clear Lake State Park, just north of Calistoga, California. As we were making teriyaki hamburger patties for the grill, yellow jackets suddenly swarmed around us, apparently thrilled with our local-kine grinds. As the swarm grew, the wasps started getting bolder and landing on our food, which was at once frightening and disgusting to say the least. However, the ultimate gross-out was when they started stealing our food – yellow jackets were picking up chunks of meat bigger than themselves and flying off with them!

Not surprising, says Dr. David Foote, ecologist and project leader for USGS Pacific Island Ecosystems Research Center, who says that yellow jackets (Vespula pensylvanica) are incredibly strong carnivores and have been seen flying while clutching large caterpillars, one of their favorite foods that they also feed their own larvae back in their nests below ground or near ground in rotting logs. Foote recently gave a fascinating presentation about yellow jackets at the Kinoole Farmers Market, and he offered some helpful tips to gardeners who might encounter them in their backyards.

A non-native species, yellow jackets first appeared in Kauai in 1919. On the Big Island, yellow jackets were probably accidentally introduced in the 1970s through shipments of Christmas trees from the Pacific Northwest. While yellow jackets inhabit most islands, they thrive best in cooler, drier parts of the islands, typically the mesic zones between dryland and rain forests. Despite their formidable sting, yellow jackets can be viewed as a gardener’s friend because they predate on non-native caterpillars that feed upon vegetable crops. Unfortunately, however, yellow jackets don’t discriminate and also eat native caterpillars and picture-wing flies, and they are likely to outcompete our native insectivorous birds and pollinators for food as well. Foote says he is currently monitoring areas where yellow jackets are present in greater numbers, where he expects to find diminishing populations of native moths and butterflies, including the pulelehua, or native Kamehameha butterfly (Vanessa tameamea), possibly due to the aggressive predation by yellow jackets.

To reduce yelllow jacket visits to your backyard you can set traps, either economical homemade ones or the fancier store-bought ones. Foote says that on Oahu, cat food (Figaro brand seafood) is used as bait, but Big Island yellow jackets seem to prefer canned white chicken breast. I like to think that it’s because everybody on the Big Island has good taste, even the insects, but Foote thinks it’s probably because the chicken is lower in fat and stays fresher longer in our humid weather than the cat food.

If you’ve ever been stung by a yellow jacket while working out in the garden, you know it hurts like fire. Though you might not have had anything more than a trivial welt, repeated stingings over a period of time can lead up to a serious allergic reaction one day and possible anaphylactic shock. When I was a child, my younger siblings and I used to enjoy capturing bees with our bare hands. Though I never got stung on the hand, occasionally I accidently stepped on them with my bare luau feet . The last time I got stung, not only did my foot blow up like a dirigible but also my face and ears puffed up. Sound dangerous? You bet. Foote cautions people like me who may be at risk to keep an Epi-Pen on hand. Ask your doctor for a prescription; the medication expires in a year, and it is around $35 per dose, but I’m convinced it is money well-spent to save a life—mine, yours or your gardening buddy’s.

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