STATE CERTIFICATION PROGRAMS: PROVIDING GRAPEVINE AND FRUIT TREE GROWERS WITH HEALTHY PLANTING STOCK

By the Washington State Department of Agriculture, the Washington Wine Industry Foundation, and the Clean Plant Center Northwest.

Author’s Note: See “Understanding Terminology” at end of article.

Four years ago, the Washington State Department of Agriculture’s Nursery Research Funding Program awarded the Washington Wine Industry Foundation and the Clean Plant Center Northwest monies for a project called “Building Awareness of State Certification Programs for Fruit Tree, Grapevine and Hop Planting Stock”. The funds from the multi-year grant were used to promote awareness and increase nursery and grower adoption of certified planting stock and to clarify industry confusion between planting stock that is clean, registered, and certified. The target audience for the confusion were grape, fruit tree, and hop nurseries as well as the tree fruit, grape, and hop growers themselves. This article (column?) was written to clarify terminology.

The Washington State Department of Agriculture Plant Services Program administers eight planting stock certification programs for various crops, including seed potatoes, grapevines, fruit trees, hops, mint, garlic, caneberries and strawberries. The Program also regularly surveys pests and diseases in Washington nurseries.

FRUIT TREES: Since the 1950s, the WSDA Fruit Tree Registration and Certification Program has served Washington’s $2.4 billion* apple, pear, and cherry fruit production system ensuring healthy, virus-tested planting stock for fruit tree nurseries.

WSDA virologists monitor trees in several different ways including visual inspection, greenhouse indexing, field indexing, and molecular testing so participating nurseries can produce certified G4 trees for wholesale and retail sale. The certification program manages over 90,000 registered G2/G3 pome and stone fruit mother trees, so that millions of certified trees and rootstocks are produced annually by 14 nurseries enrolled in the voluntary WSDA program.

The WSDA program is co-located with the Clean Plant Center-NW in Prosser Washington on the campus of WSU’s Irrigated Agriculture Research & Extension Center. WSDA collaborates with this National Clean Plant Network center as a source of fully tested G1 foundation material entering the certification program. WSDA maintains a state-of-the-art, 45,000 square foot virus-indexing greenhouse at Prosser, as well as a molecular lab, nematology lab, and field plantings of seed source trees.

The program relies on bud wood and rootstocks that have been tested for known viruses. By isolating the G2/G3 registered mother block plantings from non-certified stock, excluding virus vectors and controlling broadleaf weeds, the risk of infection with local regionally occurring viruses is greatly reduced. Planting WSDA-certified trees can mean growers have longer lived, higher yielding orchards. Certified G4 trees also give Washington nurseries export access to foreign markets for their nursery stock, which must meet rigorous international requirements for pest freedom.

For more information on enrolling in the WSDA fruit tree certification program, call Segun Akinbade at 509-786-9275.

GRAPEVINES: The availability of virus-tested grape planting stock is important to the success of vineyards and the wine industry in Washington state which is valued at $9.5 billion** in annual in-state economic impact. WSDA’s Grapevine Certification Program was established in 2002 and now inspects and tests over 200,000 registered G2/G3 mother vines at participating nurseries each year. All mother vines in the program must be sourced from clean, virus-tested G1 foundation material maintained at a National Clean Plant Center. The program requires isolation distances from non-certified stock at nurseries, vector control, and annual molecular testing of registered G2/G3 mother vines for Grapevine leafroll-associated virus 3 (GLRaV-3) and Grapevine red blotch virus (GRBV), plus a subset of samples are tested for Xylella fastidiosa. Each year, millions of certified vines are produced by four nurseries in the program and sold to vineyards and retail nurseries domestically and internationally as own-rooted vines or grafted vines (if the source rootstock is from a certified source).

The Clean Plant Center-NW at Prosser serves as a source for virus-tested G1 foundation grapevine material. These G1 vines are maintained in insect-proof screenhouses and tested regularly to ensure they are clean and virus free. Cuttings from G1 vines are used to establish registered G2/G3 mother vines at nurseries enrolled in the certification program.

The WSDA Grapevine Certification Program collaborates with WSU to conduct annual molecular testing of the registered G2/G3 mother vines for regional viruses of concern to the industry with samples submitted by participating nurseries as well as WSDA inspectors.

In addition, grape growers in Washington are protected by a state quarantine (WAC 16-483) that requires all out-of-state origin grapevines be produced under a certification program and found free of certain pests and diseases. Currently only Oregon and California have certification programs that meet Washington’s quarantine standards.

For more information on enrolling in the WSDA grapevine certification program call Benita Matheson at 360-410-1260.

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* = 2023 State Agriculture Overview – Washington, USDA NASS

* * = Washington State Wine Commission

UNDERSTANDING TERMINOLOGY: G-level, Clean, Registered, Certified, Quarantined

What Does the G-level or Generation level mean?

Generation level 1 (G1) is ‘foundation’ plant material that has been tested and found free from all viruses, viroids, and systemically infecting pathogens not specifically exempted by the Clean Plant Centers and all states with national certification programs. G1 foundation plants are maintained at a National Clean Plant Center under controlled conditions to prevent reinfection.

Generation level 2 (G2) plants are propagated from G1 plants to establish registered mother trees or vines at a nursery participating in a certification program.

Generation level 3 (G3) plants are propagated from G2 plants to further expand a registered mother block.

Generation level 4 (G4) plants are the final level in a certification program. Finished G4 trees or vines are also called ‘certified’ and are sold directly to consumers, growers and retailers.

What Is a Clean Plant?

A clean plant, also known as ‘Generation 1 (G1) foundation’ material has been tested and found free from all viruses, viroids, and systemically infecting pathogens not specifically exempted by the Clean Plant Centers and all states with national certification programs. G1 foundation plants are maintained at a National Clean Plant Center under controlled conditions to prevent reinfection.

What Is a Certified Plant?

A certified plant is one that has been grown at a nursery enrolled in a state certification program and can trace its origins to a foundation source at a National Clean Plant Center, or other approved source. The participating nursery must follow the rules of the certification program for that crop.

How Does a Plant Become Certified?

The label ‘certified’ is the result of a healthy plant being propagated using procedures to minimize infection and disease spread, and this process is legally defined by each state’s Department of Agriculture. In this process, a registered ‘mother block’ is planted at a nursery with plants obtained from a G1 foundation source. State regulations govern the details of how registered ‘mother block’ planting is done and specifies acceptable plant sources, block isolation distances and other operation parameters. Plants from the registered ‘mother block’ are propagated to produce ‘certified’ plants. If a plant is grafted onto rootstock, both the scion and the rootstock must meet these standards to qualify as ‘certified’.

For nurseries in the WSDA grapevine and fruit tree certification programs, acceptable sources for G1 foundation material are the Clean Plant Center-Northwest in Prosser or Foundation Plant Services in Davis, CA.

Why Plant “Certified”?

Planting certified material helps prevent the introduction and/or spread of many unwanted diseases. Unlike insects and many fungal diseases, the viruses, viroids, phytoplasmas and bacteria addressed by certification programs cannot be controlled by chemical sprays after plants are infected. Once disease is established, it is difficult and costly to eradicate. Planting ‘certified’ plants is the best insurance for a healthy and profitable farm.

How Do I Know if Plants are “Certified”?

Nurseries in certification programs use tags approved by the State Department of Agriculture for labeling certified plants. Certification status can also be verified on nursery invoices. Currently, Washington only recognizes certification programs in Oregon and California as meeting state quarantines for out of state grapevines.

What Is a Quarantine?

A quarantine is a restriction on transporting plant materials across specific boundaries. Quarantines are necessary to prevent the introduction and spread of unwanted pests and diseases from one area to another. Federal quarantines regulate plant imports from other countries. Washington State has quarantines for hops, grapevines, garlic, mint and seed potatoes that originate from other states and U.S. territories. These quarantines help to protect agricultural industries in Washington. Washington’s grapevine quarantine can be found under WAC 16-483.

The Clean Plant Center Northwest

The CPCNW provides propagative material from the “foundation” plants (vines or fruit trees) held at the center to propagators. Access is dependent on the ownership status of the material, with varieties in the public domain being available to all. The volume of material is limited as the center isn’t a nursery itself; its role is to get propagators material they can amplify. More information can be found at https://cpcnorthwest.com/s/

Finding Certified Plants

Only purchase plants from reputable nurseries and purchase “certified” whenever possible, but also verify that they are certified.

Call (360) 902-1874 for more information or visit the WSDA planting stock certification web pages: https://agr.wa.gov/services/licenses-permits-and-certificates/plant-permits-and-certification-programs.