New Tree Fruit Pest Meets its Match
In the course of a single year, a tiny insect has been damaging tree fruit around the globe. Spotted wing drosophila, or SWD, a type of vinegar or fruit fly, has been known in Japan, its home turf, for decades.
The fly was first detected in the United States in California in 2008 and quickly spread northwards into the Pacific Northwest. “Most drosophilids don’t attack undamaged fruit — indeed the vast majority cannot — but this one can,” said Elizabeth Beers, an entomologist and Extension specialist based at WSU’s Tree Fruit Research and Extension Center in Wenatchee.
“The female has a saw-like ovipositor and lays her eggs in the flesh of the fruit. Larvae hatch, feed and tunnel, turning fruit into a gooey mess,” Beers said. “The fly can be devastating, but we rapidly developed controls. We now have a basic pest management strategy that is being fine tuned.”
“This is a temperate-climate pest,” Beers explained, “but it seems to be adapting to our dry eastern Washington climate. So we have to discover its ecology in these arid and semi-arid regions. As predicted, it likes the maritime climate west of the Cascades.”
The management strategy for SWD consists of a couple main components, Beers said. The first step is vigilance. Members of the Washington SWD detection team are driving about 1,200 miles per week to hang and retrieve traps baited with apple cider vinegar. “When we catch one fly in a region, we warn people with susceptible crops and recommend they use continuous pest protection until harvest,” Beers said.
The other component is to understand the fly’s phenology — that is, how and when it develops in eastern Washington’s climatic conditions and, from there, when it begins attacking fruit. “I don’t think we’ve ever gathered this much data so quickly on a pest in eastern Washington,” Beers said of the effort so far. The control efforts in Washington are part of a larger, West Coast-wide study to understand and control the pest. Scientists in California, Oregon and British Columbia are also on the management task force.
The goal is to minimize the need to spray pesticides, Beers said. “For now, we must err on the side of caution until we nail that down.” The regional team is also looking for a biocontrol, a good bug that will prey on the fruit fly. “A couple parasitoids have been found that attack the pest,” Beers said.
Another possible management technique under investigation is sanitation. As Beers pointed out, “Any Drosophilid can attack damaged fruit. SWD just has a couple weeks head start. Keeping fruit off the floor may lower pressure, but so far that is just a theory.”
“We’ve got over 300 traps per week coming in here,” Beers said, “with more going to WSU entomologist Doug Walsh’s lab in Prosser.” Only a few of the traps have contained SWD, but if they do, that information will be updated in real time on the management task force’s website.
Text and photos by Brian Clark
Spotted wing drosophila updates and alerts, as well as information about chemical controls, are available on line at http://bit.ly/wsuswd.
Solving a Moldy Mystery of Turfgrass Decline in the Pacific Northwest
Two years ago, yellow, orange, and bronze circular patches began mysteriously marring the emerald-green turf of numerous putting greens on golf courses in western Washington, Oregon, and British Columbia. All told, the courses lost $500,000 in grass and greens from Everett, Washington, to Portland, Oregon.
Green keepers sent samples of the dead or dying turfgrass to the Washington State University Plant Diagnostic Clinic in Puyallup for answers. Diagnostician Jenny Glass found spores of a familiar water mold with an elegant name: Pythium. But which one of more than 150 species of Pythium?
“The presence of Pythium hasn’t really changed; it exists in the soil in some unknown quantity,” said WSU turfgrass science graduate student Nathan Stacey. “From a diagnostic perspective, Pythium spores in samples would indicate Pythium activity. The problem is that there are numerous Pythium species. We’re trying to isolate the species of Pythium that caused the decline in turfgrass.”
Last October, the WSU Puyallup Research and Extension Center, Northwest Turfgrass Association, and Washington State Commission on Pesticide Registration teamed up to investigate the problem. Stacey, Glass, Drs. Marianne Elliott and Gwen Stahnke, and scientific assistant Katie Coats collected 50 samples from 27 Pacific Northwest golf courses during the fall, winter, and early spring. Most of the samples were isolated from annual bluegrass, the predominant putting-surface turfgrass species. The researchers presented their initial findings during the 2011 WSU Turfgrass Field Day July 19 in Puyallup.
So far, Pythium torulosum, Pythium vanterpoolii, and Pythium volutum have been identified as the most common species in the golf course samples. Stacey and the team will continue to culture and sequence all samples, then determine if the pathogens are infectious by reinfecting turfgrass under varying conditions of shade, moisture, and soil temperature.
“Why did it happen? I think that question will be answered once we determine what we’re dealing with,” Stacey said.
Pythium Puzzlement Keeps Turfgrass Managers Sleepless
Diseases caused by Pythium are as effective as No-Doz® for keeping golf course supervisors awake at night, according to Jim Kerns, the field day’s featured speaker. Some have even blamed this kissing cousin to a fungus for wiping out entire fairways overnight.
Kerns, an assistant professor and Extension specialist of turfgrass pathology at the University of Wisconsin at Madison, broke down three main Pythium diseases for 50 to 60 attendees. The species that causes Pythium blight attacks above-ground foliage; those responsible for Pythium root rot destroy the root system. Still other species cause Pythium root dysfunction, another disease similar to root rot. Control measures are different for each species; a fungicide that works well to treat blight won’t work with root rot, making disease management a challenge. Since Pythium likes warm, wet conditions, cultural practices are also effective in fighting it, including limiting irrigation and increasing mowing height.
“Pythium diseases, especially those that affect the roots, can be very difficult to diagnose in the field,” Kerns said. “Therefore, if symptoms or signs develop that are characteristic of these three diseases, submit samples to a local diagnostic clinic immediately. The best way to combat these diseases is to know which one you are dealing with.”
Text and photos by Nella Letizia
Turf problems? Get help from the experts: WSU’s Plant Diagnostic Clinic provides sample processing as well as research and extension information on turfgrass in the Pacific Northwest, primarily west of the Cascade Mountains. For more information, visit http://bit.ly/q2xVhE.
Congrats to WSU Weed Olympians!
Congratulations to the WSU team of Jared Bell (Molecular Plant Sciences doctoral candidate), Alan Raeder and Misha Manuchehri (Crop Science master’s students), and Nevin Lawrence (Crop Science doctoral student) who placed first in the Western Region division of the first annual Weed Olympics held in Knoxville on July 27. Jared Bell also scored a third place win as an individual graduate student in the Western Region. All four students are advised by WSU weed scientist Ian Burke.
The Weed Olympics is an unusual event, Burke said, and can be quite challenging. Individuals are required to identify weeds and unknown herbicides, complete sprayer calibration problems, and participate in a role-playing exercise that requires solving a problem a grower might encounter.
Weeds and weed problems in Tennessee look a little different than those in Washington, Burke added, but the team of WSU students rose to the challenge. “The team worked hard the past few weeks to prepare,” Burke said.
This was the first Weed Olympics that brought student competitors from across the nation.