Good Fruit Grower

July 1

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10 JULY 2015 GOOD FRUIT GROWER S tinging nettle is a nuisance to farmers and farmworkers because of its fine hairs that sting and irritate the skin. But don't reach for the sprayer too quick. Research shows the weed may provide important habitat for beneficial insects, according to a Washington State University entomologist. Common stinging nettle (Urtica dio- ica) is a perennial and weedy plant usually confined to moist and shaded areas. Two native subspecies of U. dioica occur in the Pacific Northwest, most commonly in wetter coastal areas. In irrigated agricul- ture of central Washington it can be found near watercourses, seeps, and canals. In Europe, common stinging nettle has been found to harbor a diversity of beneficial insects and predaceous mites and support breeding populations of several butterfly species. WSU entomologist Dr. David James, who studied stinging nettle and other plant species in Washington's Yakima Valley for three years, found the weeds here, too, have value in biological control and conservation. In the WSU study, James monitored beneficial insect populations in stinging nettle (U. dioica ssp. Holosericea) patches at three locations in the Yakima Valley— near Prosser, Yakima, and Benton City— using sticky traps set out from spring through autumn during 2011 to 2013. Stinging nettle patches measured about 300 square feet in one location and 650 by 300 feet in the other two locations. Traps were attached to the upper portion of the plants from mid-May or June until mid- or early September, depending on the year, and were left in place for about two weeks before replacement with new traps. What was caught? Large numbers of beneficial insects (200 to 400 per trap) were caught at all three sites in all years. In each year, the greatest numbers of beneficial insects were trapped in early June and early July—around the same time that stinging nettle begins blooming in central Washington—and gradually declined thereafter, James reported. Many of the attracted beneficial insects may have been seeking nectar and/or pollen from nettle flowers, he explained. Beneficial insects trapped were grouped into ten categories: —Lacewings —Ladybird beetles —Predatory true bugs —Predatory thrips —Predaceous flies —Ichneumonid and braconid wasps —Anagrus wasps —Coccophagus and Metaphycus wasps Stinging nettle is BENEFICIAL Nettles provide habitat for natural enemies of pests. by Melissa Hansen Grapes PHOTOS COURTESY DAVID JAMES/WSU Humans don't care much for stinging nettle but beneficial insects and butterflies do. Research has found the moisture-loving weed can be host to large populations of beneficial bugs and predatory mites. The most abundant category of beneficial species trapped in the research was predatory bugs. Minute pirate bugs, like this one, accounted for around 95 percent of the trapped predatory bugs.

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