Photographer:Mike Ferro Source:www.bugguide.net Copyright: CC BY-ND-NC 1.0
Adult Description: Zaprionus indianus is a drosophilid fly or a “vinegar fly”. This species does not have a common English name but is called the “fig fly” in Brazil. It has very conspicuous markings that allow it to be easily recognized. They have silvery-white stripes, which are almost non-existent in New World drosophilid flies. Van der Linde (2010) created a list of characteristics to help with identification: The base color of the fly is yellowish, an even number of white stripes bordered by black that are of equal width, scutellum without white tip, composite of spines on the front leg femur, Composite spines directly on the legs, sub apical setae on fourth and fifth tergite from blackish/brownish spots.
Larvae Description: Larvae grow within the host fruit either fallen or still on the tree. They are white to yellowish and small (less than 1mm).
Host Plant: It is a generalist that breeds on fallen fruit and fruit on the tree. In Africa, it can infest 74 plant species from over 30 families. In Florida, it has been reared from: fig, apple, guava, strawberry guava, Barbados and Surinam cherries, cashew, pomegranate, sweet and sour oranges, grapefruit, peach and kumquat. Across other states it has been found on tomatoes, blueberries and vineyard blocks.
In 1999, Z. indianus was first discovered in the New World, in Brazil amongst fig crops that were having 50% yield losses. Even though it does not have a serrated ovipositor like the Spotted Wing Drosophila, sometimes it is able to infect fruit that has not fallen off of the tree; and it can outnumber SWD when adults emerge from certain plants like grapes. Researchers are looking into a relationship between Zaprionus indianus and Drosophila suzukii (SWD) because any beneficially symbiotic relationship between these two major generalist pests of crops could cause devastation across the United States. Zaprionus indianus has been reared in laboratories with native Drosophila species, however, their impact on native species remains unknown. With a wide host range and adaptability that has allowed it to expand to 15 ecologically different states in just a few years, the threat is obvious and without management, Z. indianus could seriously impact local farmers and the communities that depend on them.
Females average about 58 offspring in their lifespan. Eggs are milky white and are usually laid in small masses by multiple females. For fig flies (Ficus spp.), the eggs are laid into the ostiole. In damaged or fallen fruit the adult flies are able to lay their eggs where the damage exposes the fruit pulp. It is not clear how they lay eggs in other fruit that do not have ostioles and are still on the tree. Temperature studies of Z. indianus have demonstrated that the entire lifecycle (egg to adult) is impacted by temperature. A study in Brazil showed the lifecycle duration varied from 29 days at 18oC to 13 days at 28oC-32oC. On average, egg stage was 1 day, larval was 11 days and pupal was 5 days. Adults survive up to 150 days, but average around 80-90 days.
First discovered in Florida in 2005, the populations present are closely related to populations present to West Africa. By 2007, it was found in southern Georgia, South Carolina, Arizona, California, Mississippi and Oklahoma. In 2009, it was found near Desoto, TX in Dallas County; and North Carolina in 2010. The fly then spread widely in 2012 and was found in Connecticut, Kansas, Michigan, Pennsylvania, Virginia and Wisconsin.
Africa, Middle East and southern Eurasia
U.S. Habitat: Zaprionus indianus has become adapted in human settlements and has become a domestic species as opposed to other Zaprionus species that can be consider forest-dwelling. It can be found on endemic, introduced/cultivated or natural fruits; and is easily spread by human activity.
U.S. Present: AL, AZ, CA, CT, FL, GA, KS, LA, MI, MS, NC, SC, PA, VA, WI
Zaprionus indianus does not fully resemble any native North American drosophilid fly. However, it does resemble other species within Zaprionus, and it is usually best to have an expert confirm identification.
Field sanitation is very important to prevent the establishment of Z.indianus. This includes the removal of overripe, fallen and rotten fruit because the presence of decaying fruit only benefits the fly population. Continual survey for flies is necessary to protect crop yields of potential host plants. Studies in Brazil have shown that fig juice (diluted to 50% with water) is a better attractant in Z. indianus traps than molasses or grape juice. This fly sometimes appear in apple cider vinegar traps placed for SWD, however, this may not be the most effective way of sampling. More research of the fly’s behavior in the United States is needed.
Chassagnard, M. T. and A. R. Kraaijeveld. 1991. The occurrence of Zaprionus sensu stricto in the Palearctic region (Diptera: Drosophilidae). Ann. Soc. Entomol. France (N.S.) 27:495–496.
da Mata, R. A., Tidon, R., Côrtes, L. G., De Marco Jr, P., & Diniz-Filho, J. A. F. 2010. Invasive and flexible: niche shift in the drosophilid Zaprionus indianus (Insecta, Diptera). Biological Invasions, 12(5):1231-1241.
Nava, D. E., Nascimento, A. M., Stein, C. P., Haddad, M. L., Bento, J. M., & Parra, J. R. 2007. Biology, thermal requirements, and estimation of the number of generations of Zaprionus indianus (Diptera: Drosophilidae) for the main fig producing regions of Brazil. Florida Entomologist, 90(3):495-501.
van der Linde, K., Steck, G. J., Hibbard, K., Birdsley, J. S., Alonso, L. M., & Houle, D. 2006. First records of Zaprionus indianus (Diptera: Drosophilidae), a pest species on commercial fruits from Panama and the United States of America. Florida Entomologist, 89(3):402-404.