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Cañada College Hopes African Wasps on Campus Will Help Fight Olive Fruit Flies

The campus calls olive fruit flies 'serious pests' - and is making the study of the wasps' help toward fighting them official curriculum for some biology classes.

 

Submitted to Patch by Cañada College of Redwood City

A small African wasp that is the natural enemy of the olive fruit fly appears to be gaining a toehold in the olive trees on the campus of Cañada College in Redwood City - which could be good news for California’s olive growers.

Diego Nieto, an adjunct biology professor at the college, along with students in the school's Biology 110 class, are currently part of a statewide effort to find a way to control the olive fruit fly, whose larvae feed on the fruit of olive trees and which is considered a serious pest. California produces more than 95 percent of the olives grown in the U.S.

The olive fruit fly was first discovered in California in 1998 and was later found in San Mateo County in 2001. California is the only area in the Western Hemisphere where the olive fruit fly has been found. Scientists discovered that natural predators in California were largely ineffective in controlling the spread of the fruit fly.

"The olive fruit fly is in the family Tephrididae, which is home to several serious agriculture pests, including the Mediterranean fruit fly, Mexican fruit fly, and oriental fruit fly," said Nieto. "These flies are capable of utilizing ripening fruit for oviposition, which makes them especially damaging to fruit production."

"The fruit flies we commonly encounter, on the other hand, are in the family Drosophilidae, and are only capable of laying eggs in overripe fruit."

The widespread and rapid establishment of the olive fruit fly in California led to a worldwide search for parasitoids, an organism that spends a significant portion of its history attached to or within a single-host organism. The exploration took researchers to South Africa, Namibia, India, China and other countries.

Scientists shipped a number of parasitoids to California and studied them in quarantine before identifying two – Psyttalia lounsburyi and Psyttalia humilis – that have been released throughout the state’s olive growing region.

Both species were released at Cañada College in the 2010-11 school year.

"These wasps are specialists," Nieto said. "They have co-evolved with the olive fruit fly and are well-suited to utilize the fruit fly larvae for reproduction."

The wasps are very small and look like little ants with wings. They are also incapable of stinging people. And while they pose no threat to people or animals, they pose a major threat to olive fruit flies.

Female wasps deposit eggs into a fruity fly maggot inside of an olive. The egg hatches into a smaller larva that feeds internally on the maggot. After this maggot pupates, instead of a fly emerging, a wasp emerges to seek out additional maggots.

Since being released on campus, Nieto and his students have been monitoring the progress of the little African wasp.

"Cañada College is one of only two sites in the state where Psyttalia lounsburyi has been recovered for two consecutive years," Nieto said. "This is encouraging, but several challenges exist and could still derail this project."

Nieto said the wasp population is dependent on the density of the fruit fly population so, as the fruit fly population shrinks, so do the densities of the wasps.

"The wasps will not completely eliminate the pest," he said. "Instead, our project strives to reduce the olive fruit fly population in regions outside of commercial production."

"That includes olive trees that are used for landscaping, located in preserved open space or in residential areas that are not managed and thereby act as a pest reservoir, capable of re-infesting commercial olive groves annually."

Cañada has partnered with UC Berkeley, UC Riverside, the California Department of Food and Agriculture, and the United States Department of Agriculture on this project. A scientific paper describing the work will soon be submitted to the journal Environmental Entomology.

The college also received funding from the San Mateo County Community College District Trustee’s Fund to help integrate the research into the Biology 110 curriculum at Cañada.

"Students collectively generate hypotheses, design experimental protocols, collect olives, rear out insects, graph results, and write a paper describing the project," Nieto said. "Having hundreds of these trees on campus provides instructors and students wonderful learning opportunities that are literally steps away from the classroom."

"While I’m still in the process of refining this curriculum, I think it’s a wonderful example of how undergraduate students can participate meaningfully in active research."

What do you think of the school's project? Tell us in the comments below.

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