'Breaking bad': Insect pests in the making

March 18, 2014
Drosophila suzukii, "Spotted Wing Drosophila" is the only known pests among thousands of species of Drosophila fruit flies. The females use a large ovipositor to make holes in the skins of fruit to lay their eggs. Credit: Joel Atallah, UC Davis

Of thousands of known species of Drosophila fruit flies, just one is known as a crop pest, depositing eggs inside ripening fruit so its maggots can feed and grow. New research from the University of California, Davis, shows the similarities and crucial differences between this pest and its close relatives—and that one related fly has potential to also become a pest.

Drosophila flies, found worldwide, lay their in rotting fruit. Drosophila suzukii, also referred to as "spotted-wing Drosophila" because the male has large black blotches on his wings (as do males of several other closely related species), is able to penetrate the skins of ripening fruit and lay eggs inside.

"It was a surprise for western researchers when D. suzukii was identified as a ," said Joel Atallah, a postdoctoral researcher at UC Davis who carried out the work with Artyom Kopp, professor of evolution and ecology, and undergraduate researchers Lisa Teixeira, Raul Salazar, George Zaragoza and Mubasher Ahmed. "Previously, it was thought that Drosophila would just lay eggs on rotting fruit."

D. suzukii apparently originated in Asia and was reported in Hawaii in the 1980s. However, it wasn't identified as a pest in North America until 2008, when a UC Cooperative Extension specialist sent samples of infested strawberries to Kopp's laboratory at UC Davis, asking for help in identification.

Drosophila suzukii, "Spotted Wing Drosophila" is the only known pests among thousands of species of Drosophila fruit flies. The females use a large ovipositor to make holes in the skins of fruit to lay their eggs. On the left, Drosophila eggs in damaged fruit; center, eggs laid in holes in the skin of a cherry. On the right, the flies made holes in the skin of grapes, but did not successfully lay eggs. Credit: Joel Atallah, UC Davis

The same year, D. suzukii was found in Southern California orchards, and since then it has spread rapidly across the country.

Atallah and the undergraduate researchers analyzed the ovipositor, or egg-laying organ of D. suzukii and three other closely related species, D. subpulchrella, D. biarmipes and D. mimetica. They also offered lab-raised flies different fruits and observed whether they were able to lay eggs in them.

D. suzukii has a large, pointed ovipositor with prominent bristles. D. subpulchrella also has a large, bristly ovipositor, of slightly different shape, while the other flies have much smaller ovipositors similar to those of other Drosophila. They do have the same pattern of bristles, but they are much smaller and less visible.

In the lab, both D. suzukii and D. subpulchrella flies could penetrate the skins of cherries and raspberries and deposit eggs in them. D. suzukii flies, but not D. subpulchrella, made holes in grape skins, although they laid relatively few eggs there.

Kopp noted that even when the Drosophila flies could penetrate fruit, they were not very good at it, taking several minutes and multiple attempts.

Laying eggs inside ripening fruit is probably a recent development for Drosophila. Kopp speculated that as flies compete for good food sources in which to lay their eggs, there would be an advantage in being able to colonize fresher and firmer fruit. Eventually, this could have pushed D. suzukii to the point where it can penetrate fruit before it falls and starts to rot.

Controlling the flies will be challenging, Kopp said. Unlike the notorious Mediterranean fruit fly or Medfly, Drosophila flies are generalists with a wide range of food sources and breeding sites, and a generation time of less than two weeks.

"We want to identify which flies are dangerous and which are not," said Atallah. "D. subpulchrella has not yet been identified as a pest in the western world, but it may have the potential to become one."

Explore further: An invasive Asian fly is taking over European fruit

More information: The work was published Feb. 26 in the journal Proceedings of the Royal Society B.

Related Stories

An invasive Asian fly is taking over European fruit

March 16, 2012

Coming from the Asian continent, Drosophila suzukii has only been in Spain for a short time. Far away from slipping through into the Iberian Peninsula, it accelerated towards the north of Europe where it has already crossed ...

Discovery may lead to better lure to detect fruit fly

August 10, 2012

(Phys.org) -- A certain species of yeast that UC Davis researchers found in "almost all" their samples of raspberries and cherries infested by the spotted-wing drosophila (Drosophila suzukii) may lead to a better lure to ...

Genomic research targets fruit pest

December 4, 2013

(Phys.org) —The spotted wing drosophila, a major pest that targets berries and cherries and other fruits in the United States, Canada and Europe, is itself being targeted, thanks to groundbreaking genome sequencing at the ...

Recommended for you

Study suggests fish can experience 'emotional fever'

November 25, 2015

(Phys.org)—A small team of researchers from the U.K. and Spain has found via lab study that at least one type of fish is capable of experiencing 'emotional fever,' which suggests it may qualify as a sentient being. In their ...

New gene map reveals cancer's Achilles heel

November 25, 2015

Scientists have mapped out the genes that keep our cells alive, creating a long-awaited foothold for understanding how our genome works and which genes are crucial in disease like cancer.

How cells in the developing ear 'practice' hearing

November 25, 2015

Before the fluid of the middle ear drains and sound waves penetrate for the first time, the inner ear cells of newborn rodents practice for their big debut. Researchers at Johns Hopkins report they have figured out the molecular ...

How cells 'climb' to build fruit fly tracheas

November 25, 2015

Fruit fly windpipes are much more like human blood vessels than the entryway to human lungs. To create that intricate network, fly embryonic cells must sprout "fingers" and crawl into place. Now researchers at The Johns Hopkins ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.