New Invasive Pest Discovered in Pennsylvania


Penn State researchers recently discovered the African fig fly in Pennsylvania for the first time, giving fruit growers across the state another invasive pest to be on the lookout for.

Zaprionus indianus Gupta, commonly known in Brazil as the African fig fly (AFF), was discovered last month by the Pennsylvania Department of Agriculture in grape and pest survey traps. Dr. David Biddinger, biocontrol specialist at the Penn State Fruit Research & Extension Center in Biglerville, also positively identified the invasive fly in apple cider vinegar traps used for the seasonal monitoring of spotted wing drosophila (SWD). SWD is another recently introduced invasive pest of small fruit crops that Biddinger first detected in Pennsylvania and Maryland in July of 2012. 

After reviewing samples from 2011, Biddinger discovered AFF has been in Adams County for the last two growing seasons. "This is important, because AFF is considered a tropical pest. Not only did it survive the extremely mild winter of 2011-12, but also the more typical previous winter," says Biddinger. He points out that while SWD traps have greatly increased recently despite heavy frosts, the same vinegar traps are no longer catching AFF.  AFF is now recorded from Adams, York, Dauphin, and Clearfield counties, according to the Pennsylvania Department of Agriculture.

Biddinger says AFF is easily distinguished from all other fruit flies in the region due to a pair of silvery-white strips from antennae to thorax tip that are outlined along both sides by black stripes. "The PDA has humorously nicknamed AFF the 'speed racer fly,' since it has prominent 'racing stripes,'" he says. Adults of this species are slightly larger in size than the SWD, and the background color of the body is lighter than most other drosophilid flies commonly found in vinegar monitoring traps.

Native to Africa, the Middle East, and Eurasia, it is now found in much of South and Central America, where it is mainly a pest of figs. It was first found in Florida in 2005, where it quickly spread and outcompeted other fruit flies. New records were found for Michigan, North Carolina, and Connecticut in September of this year, and it appears to be spreading throughout the South as far west as Texas.

Since it does not have a large, sharp ovipositor like SWD females, AFF appears to only attack damaged and overripe fruit, and the harsher winters of Pennsylvania may prevent it from establishing as aggressively there as it did in Florida. "So far, numbers of adults collected in vinegar traps have been only a fraction the number of SWD collected," Biddinger explains.  "An exception is from net-collected samples in a grape vineyard where numbers of AFF greatly outnumbered SWD. While it appears from our samples that grape is not a preferred host of SWD, it may be that grape is preferred by this new fruit fly. AFF also has the potential to damage small fruits such as cherries, blueberries, blackberries, strawberries, and raspberries."

AFF's presence and damage potential in grapes and other crops is under investigation by Biddinger's lab and Kathy Demchak, Penn State small fruit specialist. Monitoring efforts throughout the state will continue next season by PDA and Penn State, and records for new hosts and county records can be forwarded to either institution.

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