Urgent Update: Spotted Wing Drosophila Confirmed In Oregon Grapes
Ξ October 12th, 2009 | → 0 Comments | ∇ A Day at a Time, Wine News |
Dr. Helmuth Rogg, entomologist for the Integrated Pest Prevention Management section of the Oregon Dept. of Agriculture Plant Division, has confirmed that both table and wines grapes have been attacked by the Spotted Wing Drosophila (Drosophila suzukii). In an email to this blog, Dr. Rogg wrote,
“[W]e hand picked wine grapes and table grapes from various vineyards in the Salem area and hatched out the SWD. So, we do know that SWD attacks wine and table grapes but we do not know the level of infestation, difference in variety, crop damage, etc. Unfortunately, we cannot conduct these experiments. We passed on our information to our colleagues from OSU and its Extension Service.”
A second email provided me reads,
Oregon Department of Agriculture has confirmed the presence of Drosophila suzukii in the following 11 counties of Oregon:
Multnomah
Washington
Yamhill (new)
Clackamas
Marion
Polk (new)
Benton
Lane
Douglas
Hood River
Umatilla
We also have confirmed the following hosts:
Strawberries
Cherries
Blackberries
Blueberries
Raspberries
Plums
Peaches
Table grapes
Wine grapes
(10/14 Update.) Please also read this 10/13 release from Oregon State.
All the fruit listed above have also been attacked by SWD here in California, with the notable exceptions of table grapes and wine grapes. I wrote a follow-up email about this development to Dr. Martin Hauser, entomologist with the California Dept. of Agriculture. He responded,
“that is bad news… I still do not have any confirmed SWD from California grapes. With the first batch of suspects, the PCR failed [owing to a technical issue]. But maybe I will have new news tomorrow.”
PCR is short for polymerase chain reaction, a DNA sequencing technology. It clearly differs from Dr. Rogg’s more field-oriented approach. The question begs whether the simple gathering of grapes from a variety of suspect California vineyards and allowing SWD larvae, if present, to emerge, might prove more diagnostically helpful. Which is to say that ‘confirmation’ of SWD in California wine and table grapes should properly be done using with both field and lab taxonomic identification protocols.
Important gains from primary field research have already been accomplished by Mark Bolda of the University of California Cooperative Extension. His focus, though principally cane berries, has resulted in great insight into early detection of the pest, how to set up traps, the appropriate baits, pesticides, both conventional and organic, and field sanitation requirements. For a recent account of his work please see my August 30th post Spotted Wing Drosophila Emergency Meeting Results and follow the various links.
Very important questions remain. What is the intensity of vineyard infestation? Are grapes a ‘preferred’ host for SWD or a fruit of last resort? What was the ratio, if any, of damaged vs. intact grapes in the Oregon samples? What grapes varieties are especially vulnerable? What ought a grower do with respect to vineyard sanitation? Will the common practice of ‘dropping’ fruit have to controlled? Will the composting of grape pomace have the unintended consequence of maintaining or even cultivating damaging populations of SWD? The list goes on, as must the research.
One of the more serious questions, if and when SWD is found in California wine grapes, is whether the presence of larvae in the interior of harvested fruit might adversely affect some quality of the must during fermentation or taste in the finished wine. This would be in addition to the skin break created by the laying of the egg, of course, clearly already a pathogen pathway. We already know that common fruit flies are effective vectors of Brettanomyces and other spoilage yeasts. Similarly do Ladybugs, very fond of vineyards, produce chemicals capable of ruining fermenting wine. This new kind of MOG (material other than grapes), the Spotted Wing Drosophila larvae, will be of pressing interest to winemakers in the very near term.
—– More breaking news on another exotic pest just detected in Napa vineyards, the European Grapevine Moth (Lobesia botrana).
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