By PAUL HETZLER

A new Asian fruit fly known as the spotted-wing drosophila (SWD) has arrived in the North Country, probably sometime in the latter part of August.

Unlike other fruit flies which lay eggs in ripe, fermenting fruit, the female SWD has a robust serrated ovipositor and is able to lay its eggs in unripe fruit. The result is that by the time the fruit is ripe, the maggots have rendered it unsalable.

This invasive insect made its first appearance in the U.S. in 2008 in California. By the fall of 2010 it had traveled as far as Michigan, and in October 2011 it was found in northern New York. It is suppressed by cold temperatures, but to what extent is not yet known.

With up to eight generations per year, by late summer the SWD population swells to the point that they can cause much damage. Because it’s most destructive in late season, and because it primarily targets soft-skinned fruit, the SWD poses the greatest risk to blueberries and fall raspberries. While the SWD does attack grapes, they’re not a preferred target, possibly because of the thicker skin. This new pest also breeds in wild native and naturalized fruit such as juneberries, blackberries, buckthorn and honeysuckle.

Anyone who’s had blueberries or raspberries turn within the span of 24-48 hours from a firm ripe condition to a near-liquid state in recent weeks may already have this insect. Market growers and gardeners can monitor for the SWD using a simple, inexpensive trap made from a quart-size plastic deli cup.

Both organic and conventional growers can protect against the SWD with a spray program. You may refer to the Cornell Pest Management Guidelines (available online at http://ipmguidelines.org/BerryCrops/ ) or call Cooperative Extension for specific recommendations.

Using a three-eighths-inch bit, drill six to eight holes in the top half of the container. Then put one to two inches of cider vinegar in the bottom, snap the lid on and hang it near your crop. Attracted by the cider vinegar, fruit flies of various kinds will fly in and drown in the vinegar.

Check the trap every 3-4 days and replenish the vinegar as needed. The trap doesn’t have to be loaded with fruit flies, but whenever it looks like a fair number have been caught—a dozen is enough—strain the vinegar through a paper coffee filter. Place the filter in a zip-locked bag with name and phone number written on it, and bring it to the Extension office for identification of the flies.

Note that Extension offices are now at the Learning Farm on the sharp curve with the flashing lights at 2043B State Rt. 68, in the first building on the left as you drive in.

For more information, feel free to call (315) 379-9192, ext. 232 or email ph59@cornell.edu

Paul Hetzler is a forester and a horticulture and natural resources educator for Cornell Cooperative Extension of St. Lawrence County.