About this Tool

This tool has a lengthy title—Identification Tool to Weed Disseminules of California Central Valley Table Grape Production Areas (or Table Grape Weed Disseminules or TGWD for short)—because it was created to address a very specific issue: the potential spread of weed disseminules via exportation of fresh table grape bunches from California's Central Valley production area to our trading partners in Australia and New Zealand. A disseminule is a plant part that can be carried away or dispersed from the mother plant and become the source of a new plant somewhere else. It is important to be able to recognize these disseminules and their taxon identities in order to prevent their unwanted spread among countries during the exportation of agricultural products. This tool includes currently known (as of 2011) weed species whose disseminules could contaminant grape bunches in the table grape production areas of Central California as described in more detail below.

How this tool was designed

This weed disseminule identification tool, TGWD, was designed by determining those plant taxa in the southern San Joaquin Valley in Madera, Kern, Fresno and Tulare Counties with disseminules that could be transported into the grape bunches before or during harvest. The major mechanism of dispersal was determined to be airborne, especially by winds strong enough to kick up the top layer of the soil bank. However, there is also opportunity for disseminule transfer when the harvested grapes are moved by wheelbarrels along the sometimes weedy areas between and around vineyard rows. Bird transport was not considered a primary means of contamination since grape bunches are typically sheltered above by the leaf canopy and growers take measures to keep birds and vermin out of their fields.

In considering which disseminules could become airborne, small size (generally less than 3 mm diameter), flattened shape and specialized structures (e.g., wings, tufts of hairs) were all taken into account.

In determining which potentially weedy taxa exist within the Central Valley table grape-growing region, we conferred with various experts and other resources including, but not limited to, Jepson Online Interchange: California Floristics (ucjeps.berkeley.edu/interchange), the Consortium of California Herbaria (ucjeps.berkely.edu/consortium/participants) and Calflora: Information on California Plants for Education, Research and Conservation (www.calflora.org). Together, these three resources provide a fairly detailed account (via herbarium specimens and anecdotal information) of the distribution of plant taxa in California. Also consulted were the two volumes of Weeds of California and Other Western States. This and other pertinent references are listed in Resources consulted. Nomenclature generally followed treatments in the various volumes of the Flora of North America, with authorities checked in the International Plant Names Index (ipni.org/)

The determination of weed disseminules with the potential to contaminate table grape clusters resulting in the 287 taxa described in this tool via informational sheets and two keys. Through text and pictures, fact sheets provide a detailed description of each taxon's potential type(s) of disseminule. Comparison charts place similar groups of three or more species side-by-side and highlight the characters that differentiate them. Both of these resources are found at Fact Sheets & Comparison Charts.

Sometimes a plant disseminule can be identified based on the informational sheets alone. When this is not the case, the two matrix-based identification keys (one that is for everything and one that is for grasses only) are available. Although these keys are based on Lucid software, each has been created as a hybrid mix of visual recognition possibilities, hierarchical analysis and matrix-based features. This design was chosen to help the user sort through the many characters in each key in a sensible and efficacious manner. For example, both keys begin with a single task—to determine whether their unknown disseminule matches any of the 10 or so disseminules in the key that are very distinctive looking. More detail on how to best use the keys is provided at How to use the keys.

Assessing risk for weedy contaminants in table grape exports to Australia and New Zealand

Australia and New Zealand each have restrictions on the types of weed disseminules that are allowed to enter their countries as contaminants of other imports (in this case, table grape bunches from Central California). Some lists of allowed and unallowed species were created during the development of the individual Work Plans for California Table Grape Exports to each country. Both Australia and New Zealand also have “master lists” concerning weed disseminule imports to their countries under virtually any conditions. On each fact sheet of this tool are indicators of the importer's assessment of a particular taxon based on both types of lists as of mid-2011. Note that the master lists are updated periodically (at least once a year) and should be checked for updated or revised information.

For Australia, the Work Plan lists include Weeds of Quarantine Significance to Australia Associated with California Table Grapes from the Work Plan for the Pre-Clearance of California Table Grapes, as well as additional lists at the Table Grapes from the USA website (www.daff.gov.au/ba/ira/final-plant/tablegrapes-usa). The lists are Attachment 3 of the Policy Determination (Feb 12, 2002) document and Section 6.2, which is called Weed Seed Contamination of Table Grape Imports, of the Draft IRA Report (March 1999).

Inspectors also use three lists from the most recent version of the Quarantine Proclamation 1998 (www.comlaw.gov.au/Series/F2011C00625). This document is updated about once a year. The most recent version available for use when creating this weed identification tool was published in July, 2011. The site includes The Permitted Seeds List (Volume 2, Schedule 5), Kinds of Plants That Must Not Be Imported (Volume 2, Schedule 6) and Plants that are Quarantinable Pests (Volume 1, Schedule 4, Part 2). Plants that are NOT on The Permitted Seeds List are also considered “prohibited from import.”

For New Zealand, the most recent Work Plan document for California table grapes is called Import Health Standard Commodity Sub-class: Fresh Fruit/Vegetables: Table grapes, (Vitis vinifera) from the United States of America—State of California (May 3, 2010) and is on the web at www.biosecurity.govt.nz/files/ihs/grape-us.pdf.

For the offshore inspection of table grapes, New Zealand also uses the following two “master lists” — Biosecurity Organisms Register for Imported Commodities (BORIC) (www.maf.govt.nz/biosecurity/pests-diseases/registers-lists/boric/) and MAF Biosecurity Authority Plants Biosecurity Index (BPI) (www1.maf.govt.nz/cgi-bin/bioindex/bioindex.pl). BORIC is updated every 2 weeks and lists both “regulated” and “non-regulated” species. The most recent version used when creating this tool was published in October, 2011.

BPI is the list of species approved or not for import for sowing and is updated periodically. The version accessed for this tool was updated in September, 2011. Species on this list are described as “Entry prohibited,” “Basic,” “Requires assessment,” or something more specific. “Basic” species must meet basic import requirements (see site) but are otherwise allowed to be imported. Documents at both of these sites state that a species not on these lists is prohibited from import.

Using the foregoing lists, each taxon in this weed identification tool is characterized with one or more of the following codes.

AUWP This means that the taxon is listed as prohibited on one of the Australian Work Plan documents.
The taxon is absent from The Permitted Seeds List and/or is listed on one of the other Quarantine Proclamation 1998 lists.
The taxon is present on The Permitted Seeds List and is NOT listed on one of the other Quarantine Proclamation 1998 lists.
This means that there is confusion, e.g., the taxon was present on The Permitted Seeds List, but also listed as prohibited on one of the other Quarantine Proclamation 1998 lists.
The taxon is listed as “regulated” on the New Zealand Work Plan document.
The taxon is listed as “non-regulated” on the New Zealand Work Plan document.
The taxon is listed as “regulated” at the BORIC site or is not listed at all at the site.
The taxon is listed as “non-regulated” at the BORIC site.
The taxon is listed as non-“basic” at the BPI site or is not listed at all at the site.
The taxon is listed as “basic” at the BORIC site.
There is confusion, e.g., when the nomenclatural treatment in the database does not exactly match the nomenclature of the tool.

In searching these lists, every effort was made to search common synonyms for each taxon. Nevertheless, the United States government is not responsible for any mischaracterizations of the import status in Australia or New Zealand of a particular taxon based on nomenclatural changes.


Identification Tool to Weed Disseminules of California Central Valley Table Grape Production Areas (TGWD) was a collaborative creation under the direction of Deena S. Walters at the U.S. Department of Agriculture's (USDA) Center for Plant Health Science and Technology (CPHST) laboratory in Fort Collins, Colorado and working with scientists Deborah Meyer, Jim Effenberger, and Robert Price at the California Department of Food and Agriculture (CDFA) in Sacramento, California. Funding was provided by the USDA's Foreign Agricultural Service (FAS) and by CPHST. Photographic and editorial support was provided by Christina Southwick of CPHST; web design support came from Sean McCue of Sean McCue Design.

Most of the material for photography was provided by the Seed Lab or Herbarium (CDA) in CDFA's Plant Pest Diagnostis Center and verified by CDFA scientists, including the curators of the herbarium—Fred Hrusa and Dean Kelch—as well as the Seed Lab scientists Deborah Meyer, Jim Effenberger, and Robert Price. Supplementary material came from other herbaria including the University and Jepson Herbaria (UC/JEPS) at the University of California—Berkeley, the herbarium at the University of California—Davis (UCD), the Rancho Santa Ana Botanic Garden Herbarium (RSA), the Rocky Mountain Herbarium (RMH) at the University of Wyoming (special thanks to Curator Ron Hartman), and the herbarium at Colorado State University (CSU). Grass expert Robert Freckmann of the University of Wisconsin—Stevens Point donated material of the grass Dichanthelium acuminatum for photography.

All photographs were taken at the laboratory in Fort Collins by Deena Walters and Christina Southwick unless otherwise noted in the figure's caption. Various photographs that had been taken by Julia Scher or Deena Walters were borrowed from the USDA identification tool entitled Federal Noxious Weed Disseminules of the U.S. A significant contribution of photographs came from the publication Weeds of California and Other Western States, published by the Regents of the University of California in 2007. Special thanks to Robert Sams, Michael Poe, and Evett Kilmartin of the University of California's Agriculture and Natural Resources Communication Services for facilitating transfer of over 350 of those images. Permission was also obtained to use several photographs from the following individuals—Neal Kramer (kramerbotanical@yahoo.com), James M. Andre (Granite Mountains Desert Research Center, University of California—Riverside) and John Macdonald (RSABG Seed Program, Rancho Santa Ana Botanic Garden).

Several original drawings were borrowed from the USDA identification tool entitled Federal Noxious Weed Disseminules of the U.S. Drawings by Lynda E. Chandler are from Gunn and Ritchie (1988); images were also redrawn from Fahn (1990) and Zomlefer (1994). See Resources consulted for more details on these publications. Supplementary drawings were provided by Sean McCue (Sean McCue Design).

Appreciation goes to the reviewers of the keys, fact sheets, and overall tool. Reviewers included the California Table Grape Commission, Norma Diaz (PPQ), Timothy Jones (Louisiana State University), Mark Towata (PPQ), Ruojing Wang (National Seed Herbarium, Canadian Food Inspection Agency), and Rodney Young (PPQ). Reviewing such an extensive tool was not an easy task!

Finally, special thanks to John Loyd and Barbara Maehler of USDA-APHIS-PPQ for their support and guidance during the process of tool development.

Copyright, citation and disclaimers

USDA logo and link to its website    APHIS logo and link to its website    CDFA logo and link to its website

Identification Tool to Weed Disseminules of California Central Valley Table Grape Production Areas (TGWD) was developed by the Center for Plant Health Science and Technology (CPHST) in collaboration with the California Department of Food and Agriculture (CDFA). CPHST is the scientific support organization for the Plant Protection and Quarantine (PPQ) division of the Animal and Plant Health Inspection Service (APHIS) in the United States Department of Agriculture (USDA). Leadership for this project was provided by Deena S. Walters at the CPHST laboratory in Fort Collins, Colorado. Major scientific collaboration was provided by scientists Deborah Meyer, Jim Effenberger, and Robert Price of CDFA in Sacramento, California.

Most of the content in TGWD is a work of the U.S. Government and is in the public domain. Public domain information may be freely distributed or copied, but it is requested that appropriate acknowledgement be given, preferably as follows:

Walters, D.S. 2011. Identification Tool to Weed Disseminules of California Central Valley Table Grape Production Areas. USDA APHIS PPQ CPHST Identification Technology Program, Fort Collins, CO. http://idtools.org/id/table_grape/weed-tool/ [date you accessed the site].

Photo by D. Walters & C. Southwick may be added for attribution of images.

Not all materials in TGWD are in the public domain. Some images (photographs and drawings) that were obtained from individuals or organizations may be protected by copyright. The origin of most of these images has been indicated in the tool in image captions or on the Acknowledgements section above. You may need to obtain permission from the copyright holder to use, reproduce or distribute these images. For information on authorship of individual images, how to reach copyright holders or to offer any feedback or comments, contact ITP:


While the project scientists have made every effort to provide accurate information in TGWD, they, CDFA and USDA-APHIS-PPQ-CPHST specifically disclaim all legal liability with respect to the accuracy, completeness or usefulness of any information contained in this tool. The scientists and associated institutions shall assume no legal liability for any damages, including direct, indirect, consequential, compensatory, special, punitive or incidental damages, arising from or relating to the use of TGWD or the information and materials provided by or linked from TGWD.

Some web pages in this tool provide links to Internet sites for the convenience of the users. The project scientists, CDFA and USDA-APHIS-PPQ-CPHST are not responsible for the availability or content of these external sites, nor do they, CDFA and USDA-APHIS-PPQ-CPHST endorse or warrant the products, services or information described or offered by these Internet sites.

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