Cornell Cooperative Extension of Chautauqua County has confirmed a new fruit pest, Drosophila suzukii, the Spotted Wing Drosophila (SWD), in the town of Chautauqua. SWD is an invasive pest of Asian origin that was first detected in the continental United States in California in 2005 and has since spread to several western and eastern states. It was first reported in New York in 2011.
Last week, a homeowner from the town of Chautauqua contacted the Master Gardener Helpline at the CCE office regarding an abundance of maggots in her late season blueberry crop. Master Gardeners followed up on this report to confirm the identity of this new pest on Tuesday.
SWD looks similar to small fruit flies found on overripe bananas, which are more of a nuisance than a serious economic threat to fruit growers. However, unlike these other flies, which typically feed on overripe or deteriorating fruits, SWD feeds on healthy, ripe, marketable fruits leading to damage and contamination with maggots. In particular, SWD will feed on thin-skinned, soft fruits such as raspberries, blackberries, blueberries, strawberries, grapes, plums and cherries. Sometimes the symptoms won't show until after the fruits are harvested and sometimes not until the fruits are in possession of the consumers. In addition to the damage caused directly by the larvae, the feeding makes the fruits susceptible to infestation by other insects, rot fungi and bacteria. The larvae will then leave the fruits to pupate and later emerge as adults.
There is potential for significant impact from this pest, especially for mid-summer and later-maturing fruit, when populations tend to increase. Risk of marketing fruit contaminated with SWD larvae is high resulting in rejected shipments and consumer complaints. In areas where SWD has been established longer (e.g. Michigan) some growers have resorted to frequent pesticide applications thereby increasing economic and environmental costs as well as potentially disrupting established IPM programs.
The SWD is a small fly, only 2-3 mm long, with yellowish brown coloration and prominent red eyes. Male SWD have dark spots on the wing tips. SWD larvae are white with a cylindrical body that tapers on both ends. The adult flies are difficult to distinguish from other small flies; however, if you find an abundance of small, white maggots in what were apparently healthy fruits at the time of harvest, contact the Chautauqua County Cornell Cooperative Extension Offices.
Monitoring and early, on-going management is very important for this pest. Traps baited with vinegar have proven successful in capturing sometimes large numbers of adult SWD. Traps should be frequently checked, adding fresh vinegar. Research is ongoing to improve trap efficiency and develop a better early warning system. Fruit should also be inspected for evidence of larval feeding.
For more information on the identification, monitoring and management of SWD, or if you suspect you have SWD, please contact Cornell Cooperative Extension of Chautauqua County (716) 664-9502 x 202, 204 or 224 or go online to: www.fruit.cornell.edu/berry/pestalerts/drosophilapestalert.html