Texas Invasive Species InstituteDrosophila suzukii
Spotted Wing Drosophila
Class: Insecta
Order: Diptera
Family: Drosophilidae
Photographer: USDA-APHIS
Source: http://invasivore.org/2011/02/
Adult Description: Drosophila suzukii is from the same genus as the D. melanogaster which is a commonly used organism in genetics. Unlike other pomace/vinegar flies that forage off of over-ripened or rotten fruit, the Spotted Wing Drosophila (SWD) attacks fresh fruit before they are harvested. These small (3-4mm), yellowish-brown flies with red eyes are able to attack fresh fruit because the females have a serrated ovipositor (pictured right), which allows them to lay their eggs inside the fruit much like fruit flies from the family Tephritidae. The antennae are short and stubby and males have a distinguishing dark spot along the front edge of each wing (pictured left). Spotless males are possible, but are rarely observed.
Larvae Description: The larvae cause the most damage to the fruits by eating them from the inside out. They are reddish brown in color and cylindrical with two projections at the ends. They are 2-3mm in length and pupation can occur within or on the outside of the fruit.
Host Plant: Several important crops such as: Asian pears, Blackberries, Blueberries, Caneberries, Cherries, Cranberry, Currants, Loganberries, Orange jasmine, Peaches, Plums, Raspberries, Strawberries and Wine Grapes
Ecological Threat: With a wide range of economically important crops, the threat of this invasive fly is apparent. Also, these flies reproduce rapidly and have high fecundity, which means they can overrun crop fields quickly. It has been observed to cause up to 80% crop loss in one year. The first symptom of infestation is scarring on the fruit surface left by ovipositing females. Damage is primarily caused by the larvae feeding within the fruit on the pulp and turning it brown and soft. Infested fruit collapse around the feeding site quickly and then rot due to secondary infections like mold.
Biology: Drosophila suzukii reproduces rapidly and completes its lifecycle in one to two weeks. Adults live for about 3 to 9 weeks. In Japan, 13 generations can be created in a year while in California, only 10 generation are created. A single female can lay up to 60 eggs/day and 600 in her lifetime. The eggs are laid singly and are randomly laid within the fruit and multiple larvae clutches can be present on the same fruit. As the rotten fruit drops the larvae emerge from the fruit to pupate; if they pupated within the fruit they then emerge as adults.
History: SWD was first established in Hawaii in 1980. By 2008, it was found in California on caneberry and strawberry plants. In 2010, it was found in Michigan and Oklahoma and by 2011, it had invaded New England. Since then, it has spread to the Southeastern and Midwestern United States, reaching Nebraska and Texas in 2013. It has been found in one county in Eastern Texas, where several family and commercially-owned fruit orchards that grow, strawberries, blueberries and other host plants are nearby.
U.S. Habitat: Prefers a moderate and humid climate but it can tolerate cold conditions. It can be found anywhere that the host plants are able to grow. SWD is less active when temperatures are above 86oF or below freezing.
Distribution
Native Origin: Southeast Asia
U.S. Present: CA, FL, HI, IA, LA, ME, MI, MT, NB, NC, NY, OR, SC, TX (1 county), UT, VA, WA and WI
Resembles/Alternatives
Looks like other Drosophila species that are found in Florida. Consequently, expert examination by a specialist is needed for confirmation.
Management
Drosophilia flies are called “vinegar flies” because they can be attracted by vinegar. This can be used as a trapping method by using apple cider vinegar. Bucket-style traps can be effectively used for monitoring D.suzukii. Studies have shown that mixtures of apple cider vinegar and wine can catch up to 3 times more specimens than just wine or apple cider vinegar alone. These types of traps work best when placed in cool and shady areas in the crop fields.
Field sanitation is critical to prevent the spread of flies. All damaged fruit should be removed and destroyed by disposal in closed containers, not by burial, because adults have been observed to come back to the surface. Thankfully, Drosophila are weak fliers, but spread easily by infested fruits. There are braconid wasp parasitoids that are potential biological control agents, particularly Orius insidiosus, but more research needs to be performed to confirm the benefit of this wasp. Insecticides are effective against SWD, conversely, since this fly infests ripening fruit, the chemicals must have shorter pre-harvest intervals.
References
Internet References
http://www.entnemdept.ufl.edu/creatures/fruit/flies/drosophila_suzukii.htm
http://citybugs.tamu.edu/2013/09/13/a-berry-bad-pest/
http://giannini.ucop.edu/media/are-update/files/articles/v13n3_2.pdf
http://www.cabi.org/isc/?compid=5&dsid=109283&page=481&site=144
http://agfax.com/2013/10/11/nebraska-spotted-wing-drosophila-now-state/
