Posts Tagged: spotted wing drosophila

UCCE advisor recognized for pest control work

Mark Bolda, UC Cooperative Extension advisor in Santa Cruz County, was recognized by the North American Raspberry and Blackberry Association in January for his research and extension work on spotted wing drosophila, reported The Grower.

Bolda received the 2013 Distinguished Service Award at the association's North American Berry Conference, Jan. 30, in Portland, Ore. He first identified drosophila as a new pest for coastal California berry growers in late 2008. Bolda led field trials to determine the best trap designs and trapping methods and conducted research to help develop an integrated approach to control the new pest.

A photo of spotted wing drosophila on a raspberry from Bolda's Strawberries and Caneberries blog.

Yeast discovery may lead to better lure to detect fruit fly

Drosophila suzukii larva damage cherries. 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 detect the invasive pest in the field. A research team from the UC Davis Department of Entomology, the Department of Food Science and Technology, and a visiting professor from the University of Extremadura, Spain, found that the yeast, Hanseniaspora uvarum, appeared in just about every cherry, raspberry and larva of the spotted-wing drosophila (SWD) that they sampled at collection points in Davis, Winters and Watsonville. The agricultural pest, native to southeast Asia and now found in many parts of North America, was first observed in California in the fall of 2008 in the central valley, but was not identified until early 2009. It is reported to attack soft-skinned, ripening fruits, and has been a particular problem for raspberry and cherry growers in California. The research team – composed of Phaff Yeast Culture Collection curator Kyria Boundy-Mills of the UC Davis Department of Food Science and Technology; Frank Zalom UC Cooperative Extension specialist in the Department of Entomology at UC Davis and integrated pest management expert; doctoral student Kelly Hamby in the Zalom lab; and UC Davis visiting  professor Alejandro Hernandez of University of Extremadura, Spain – published their work in a recent cover article of the journal Applied and Environmental Microbiology, the No. 1 cited journal in microbiology. "This represents the first look at potential yeast associations of Drosophila suzukii," said Hamby. “We are now testing to see if this species will be a good lure to detect this fly in the field,” Boundy-Mills said. “When we started the work we hoped to find candidate yeast species that could be used to improve the bait in Drosophila suzukii traps,” Hamby said. “Fruit flies are regularly trapped with apple cider vinegar or baker's yeast and sugar plus water so these were the traps that were originally recommended for monitoring when SWD first invaded California in 2008.” “Unfortunately, these lures trap all fruit flies, and many other non-target insects, so the hope was that we might be able to design a more selective and attractive lure by identifying a more specific yeast that is used by SWD,” Hamby said.  “Often Drosophila have interactions with yeast communities, and communities often vary between host plant species, so it was a bit of a surprising that we found Hanseniaspora uvarum so often, though, we used only culture-based methods so other yeasts may be present that are hard to culture,” Hamby said.  Hannah Burrack, a former Zalom lab graduate student (now an assistant professor and Cooperative Extension specialist in the Department of Entomology, North Carolina State University) originally found that olive flies were more attracted to yeasts that were isolated from the flies themselves than to the Torula yeast bait that is commercially available for olive fruit fly management, Hamby said. Yeast ecologists have investigated Drosophila-yeast interactions for more than 60 years, Hamby said. “The work that had been done with Drosophila was the impetus for Hannah Burrack's work, therefore, we thought that we really had a great study system in SWD.” Zalom and Burrack had earlier collaborated with Boundy-Mills, “so our lab already had an established collaboration with a yeast systematist before we dreamed up this project,” Hamby noted. “Kyria curates a huge UC Davis yeast collection and all the yeast strains we found were deposited into the Phaff collection.” Boundy-Mills pointed out that SWD is causing major crop damage to soft fruits such as berries and that better detection and control methods are needed.   In their journal article, the authors wrote that “D. suzukii is unique in that it oviposits on marketable fruit relative to overripe or damaged fruit, and its injury facilitates colonization by other Drosophila species. If untreated, it is capable of causing a potential $860 million of revenue loss annually to blackberries, raspberries, and cherries in California, Oregon, and Washington. Knowledge of potential yeast associations could be used in lure development.” Zalom said the pest is a major problem in the area for backyard cherries. “Many residents have not been able to harvest cherries for several years now.”

Monitoring guidelines change for new pest threat

One of the newer exotic pests in California, spotted wing drosophila, caught growers and researchers off guard last year, according to a special report by Dow AgroSciences that was published today in American/Western Fruit Grower magazine.

The Asian native pest was first detected in California in 2008 along the coast. By then, it had already established itself to an extent that CDFA deemed it impossible to eradicate. SWP has increasingly been found inland, especially in the sweet cherry districts around Stockton and Hollister, the article said.

“That’s when the wheels came off the wagon and a lot of people got hurt very badly,” the story quoted UCCE specialist Robert Van Steenwyk. “Then it raced up and down the West Coast.”

SWP has been found in many California counties infesting ripening cherry, raspberry, blackberry, blueberry and strawberry crops. It has also been observed attacking other soft-flesh fruit such as boysenberry, varieties of Japanese plums, plumcots and nectarines.

Early recommendations that growers need only monitor for male SWP, which are much easier to find because of their distinctive spotted wings, was wrong.

"What researchers didn’t know was that the sex ratios were extremely variable. Some growers got hit with bad infestations because, while they were looking for spotted wings, female SWD were attacking their fruit," the story said.

More information on SWD monitoring and control are outlined on the UC IPM website. Potential economic impacts of the pest were documented in a Giannini Foundation of Agricultural Economics report.

Spotted wing drosophila larvae in a cherry.

Spotted wing drosophila raising cain in California

A fruit fly that made its first California appearance four years ago in Watsonville  - spotted wing drosophila - can be managed with three basic common-sense techniques.

"It's going to come down to trapping, monitoring and good sanitation," Mark Bolda, University of California Cooperative Extension farm adviser in Santa Cruz, Monterey and San Benito counties, told a group of growers in January, according to an article in the Santa Cruz Sentinel.

"Most of the industry is in this room right now," the story quotes Bolda. "That's why it's important to work together. You can't leave discarded fruit in the fields anymore. Neither can your neighbors. It's going to be a breeding ground for flies."

Last July, Bolda wrote in his Strawberries and Caneberries Blog that spotted wing drosophila had infested cherries, raspberries, blackberries, blueberries and strawberries in California.

"It has been found in many (I think the number was 21) counties across California, as well as several other states," Bolda wrote.

However, he told farmers last month he is optimistic that growers and researchers are headed in the right direction.

"I think the worst of it is behind us," he said. "Really, it's standard pest management. We just got caught by surprise, initially. We have much more work to do. We still haven't gotten really clear results."

At Grape Day this week in Lodi, the opening speaker, UCCE farm advisor Paul Verdegaal, focused on vine mealybug and spotted wing drosophila, reported the Lodi News-Sentinel.

He said spotted wing drosophila resembles the common vinegar fly, which only attacks rotted fruit, but will also lay eggs in healthy fruit with soft flesh, such as grapes, cherries and strawberries.

Reporter Jordan Guinn wrote that there are still many unanswered questions about the pest, but scientists know one thing for sure: It's spreading rapidly. The pest came from Japan and is now a regular resident in orchards and vineyards in California, Oregon and Washington.

Up-to-date information on spotted wing drosophila can be found on Bolda's blog.

Detailed background information about spotted wing drosophila is available on the UC Integrated Pest Management Web site.

Spotted wing drosophila.

The power of a personal statement

Working in media relations, we don't always think about the very-well-read section of the newspaper's editorial pages, the letters to the editor. But it can be a powerful outreach tool.

The UC ANR blog, written by Mike Bolda and titled "Strawberries and Caneberries," was recently plugged in a letter to the Ashland (Oregon) Daily Tidings by none other than Mike's sister, Karen Bolda.

An Ashland resident, Karen Bolda wrote:

"The Nov. 12 article on the discovery of the harmful fruit fly is very timely. My brother, who works with the University of California Agriculture Extension, has been trying to get the word out on this infestation this summer, and he was excited to hear that Southern Oregon is aware of the existence of this variation of the fruit fly. He wanted me to pass on the link to his blog for anyone who wants to find out more information about the life cycle, or stay in the loop of this very current issue for berry growers: ucanr.org/blogs/strawberries_caneberries."

Mike Bolda has posted detailed information about spotted-wing drosophila and many photos in these two blog postings:

• The importance of enhanced sanitation for management of the spotted-wing drosophila
• Use of chemical pesticides to control spotted-wing drosophila

The UC IPM Web site also contains information and photos of spotted wing drosophila, including male and female adults, and a maggot in fruit.

Female spotted-wing drosophila

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