Gary Ballard worries that contaminated soils can infect clean plants.

Gary Ballard worries that contaminated soils can infect clean plants.

Grape selections that come out of the Clean Plant Center-Northwest Grapes are certified to be free of known grape viruses and crown gall disease, making them the cleanest in the nation. But years of work to test and maintain the clean plant material can quickly be undone by planting in dirty soil, says manager Gary Ballard.

For nearly a decade, Ballard has managed the grape program at Clean Plant ­Center-Northwest Grapes (formerly the Northwest Grape Foundation Service), overseeing the quarantine testing procedures and maintenance of the four-acre grape foundation block. Since the grape foundation program was re-invigorated in the early 2000s, more than 325 grape selections have gone through the quarantine program, with 32 selections entered this year.

Any grower can arrange for a selection to come into the program. The process is virtually free if the selection will be made public. Fees for exclusive selections can run into the thousands of dollars when years of maintenance in the foundation block are accounted for, said Dr. Markus Keller of Washington State University.

No other grape certification program indexes for crown gall, Ballard said, which makes the Northwest program the cleanest in the nation.

“There’s no agribacterium in any of the plant material that goes into the foundation block,” he said emphatically. “But it’s easy for a grower to compromise the no-crown-gall status by planting in dirty ground. Growers need to realize how easy it is to take years of work and throw it away by being careless.”

Grape leafroll disease has been known to move into even clean vineyards, Ballard said, adding that grape mealybug, a known vector, can bring the disease into the vineyard by hitchhiking on equipment, clothes, and riding the wind. “But if you start clean, with certified vines, you can at least slow up the progression of the ­disease.”