African Fig Fly: Another Invasive Drosophilid Fly Discovered in Pennsylvania
Posted: November 16, 2012
A. Spotted Wing Drosophila (SWD) male in comparison with the African Fig Fly (AFF). B. African Fig Fly (AFF) and its black-bordered, white “racing stripes”.
Reviewing SWD samples from 2011, Dr. Biddinger also found it had been present in Adams county in the fall of 2011, so it has been here for at least two seasons. For what is considered to be a tropical pest, this is important because they not only survived the extremely mild winter of 2011-12, but also the more typical previous winter. Of note, however, is that while SWD trap catches have greatly increased in the last two weeks 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.
Z. indianus adults are easily distinguished from all other fruit flies in our region because of a pair of silvery-white stripes from antennae to thorax tip that are outlined along both sides by black stripes. A humorous nick-name given to the fly by PDA has been the “Speed Racer Fly” since it has prominent “racing stripes.” Adults of this species are slightly larger in size than the Spotted Wing Drosophila and the background color of the body is lighter than most other drosophilid flies we commonly find in our SWD 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 out-competed 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. Z. indianus is considered as a generalist insect feeding on various tropical fruits, but it has potential to damage small fruits (cherries, blueberries, blackberries, strawberries, and raspberries). In Pennsylvania, so far it has been found later in the season and mostly in grapes, but has also been found in SWD monitoring traps in cherry, raspberry and blackberry plantings. Its presence and damage potential in grapes and other crops is under investigation by Dr. Biddinger’s lab and Penn State small fruit specialist, Kathy Demchak. Monitorings effort throughout the state will continue next season by PDA and Penn State and records for new hosts and new county records should be forwarded to either institution.
Since it does not have a large, sharp ovipositor like SWD females, AFF appears to only attack damaged and over-ripe fruit and the harsher winters of Pennsylvania may prevent it from establishing as aggressively here as it did in Florida. Indeed, so far numbers of adults collected in vinegar traps have been only a fraction the number of SWD collected. An exception, however, has been 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. There is also concern in the South that it will become a pest of blueberries.
- Tree Fruit Research Entomologist