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Pennsylvania Insect and Disease Update: Spotted-winged Drosophila — SWD

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Pennsylvania Insect and Disease Update: Spotted-winged Drosophila — SWD

Exotic fruit fly Drosophila Suzukii

Speaking at the Penn State Forest Health, Insect and Disease seminar (3/27/18) Scott Stoleson, Research Wildlife Biologist, USDA Forest Service, discussed the potential implications of the exotic fruit fly, Drosophila Suzukii (Spotted-winged Drosophila — SWD), on the Allegheny National Forest (ANF) Ecosytem.

The Spotted-winged Drosophila (SWD) is a non-native pest that appeared on the West coast in 2008 and has spread rapidly across the continent. It was discovered in the Allegheny National Forest (ANF) in 2016.

Spotted-winged Drosophila -- SWD iD

A distinguishing feature of the SWD is its saw-like ovipositor that enables it to lay eggs inside unripe fruits, unlike its other relatives, which lay their eggs on/over fruit. Once the SWD has laid her eggs it will prevent the fruit from ripening. The effects of the SWD on commercial fruit has been studied globally, however the impacts on native forest ecosystems remain virtually unknown.  Recent studies in the ANF have shown that when the wild blackberry (Rubus allegheniensis) berries began to ripen, large numbers of the fruit flies appeared, and essentially destroyed the entire crop within 2 weeks. Another study of black cherry (Prunus serotina) seed viability revealed 30% of sampled fruit contained SWD maggots. Scott concluded that considering the importance of both blackberry and black cherry fruits to birds, rodents, bear, and other species, their loss to SWD is likely to have a direct impact on wildlife populations, and perhaps tree regeneration patterns as well.

Male Spotted Wing Drosophila can be identified by the dark spot on the tip of each wing as well as two dark spots on their front legs. Female SWD lack the spots but rather can be identified by their rather sinister looking saw-like ovipositor on their rear end.



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