When Ashley Johnson ventured into Washington’s vineyards last summer in search of pesky leafhoppers, the insects were almost nowhere to be found. That is, until she began receiving calls from organic grape growers.
“We didn’t realize that’s where we’d find them,” she said, “but the only people who reported they had leafhoppers were organic vineyards.”
Ashley Johnson examines a vial of leafhoppers collected from the Columbia Basin as a part of WSU research into insect populations in vineyards.
As a viticulture and enology student, Johnson dove into entomology as part of her undergraduate research. At the WSU Irrigated Agriculture Research and Extension Center in Prosser, Wash., she was introduced to two pests that cause serious damage to Washington’s vineyards: Virginia Creeper Leafhoppers and Western Grape Leafhoppers.
When she spotted the insects, or their markings on the leaves, she sucked the adults up with a “bug vacuum,” or if they were nymphs, she took them from field to the lab and delicately swept them with a paintbrush into vials.
She returned to an entomology lab Pullman in the fall with thousands of specimens and began to run them through a genetic analysis to look at their DNA. Since the two leafhoppers don’t start to look different from one another until they reach the adult stage, testing and knowing the variation in their genetic material can help viticulturists spot a potential problem early on.
“A lot of people out in the fields thought they had Western Grapes, but so far from the data shows there are a lot more Virginia Creepers,” she said. Which can be a problem for growers, she says, since Virginia Creepers are vectors of red blotch disease.
Grape virologist Naidu Rayapati and his lab discovered red blotch disease and added it to the list of known grapevine disease last year.
“We’re hoping to one day be able to collect leaves, run them through a genetic analysis (PCR), spit out the data, and then immediately tell growers what the population genetics is like in their vineyards,” Johnson said.
Both insects leave yellow speckles, called stippling, on the leaves, which makes it possible for growers to recognize their presence. Both types of leafhoppers also eat the leaves, which are used for photosynthesis and provide the plant with sugar and nutrients. So when the insects eat the leaves, the grape berries don’t get the sugar build up ultimately necessary for a quality winemaking process.
While Johnson graduated in May and left her leafhoppers behind, the impact of her work will continue to influence the wine industry where she now works. After graduating from WSU in May, she began her career working as a winemaker at Columbia Winery in Richland, Wash.
“It’s been a huge learning experience,” she said. “I’ve been really grateful to Doug and Laura and the college for the internship opportunity.”
Johnson’s undergraduate research was supported with funding from the WSU Viticulture and Enology Undergraduate Internship program, the WSU CAHNRS undergraduate internship program, the Washington Wine Advisory Council, and the Washington Wine Commission
For more information on WSU research and extension involving viticulture, click here.