Photo: Cheatgrass in southwest Montana.© 2020 Delena Norris-Tull
Interview with Dr. Robert Price, California Department of Food and Agriculture
Email: robert.price@cdfa.ca.gov Work phone: 916-738-6700
Interview by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western
(Interview reviewed & approved Sept. 29, 2020)
I had a telephone interview with Dr. Robert Price in September, 2020. Dr. Price works for the Plant Pest Diagnostics Branch of the California Department of Food and Agriculture (CDFA) as a Senior Seed Botanist/Specialist. He is also the CDFA Primary State Botanist. He is a certified seed analyst and a plant taxonomist.
Dr. Price provided information to assist me in sorting out the various lists of noxious weeds and invasive plants in California. There is an official State list of “noxious weeds” listed in the California Code of Regulations (CCR 4500).
Many of the plants on that the official list have also been classified, using the State’s official Pest Risk Proposal rating system. Each species subject to analysis as a possible noxious weed species is rated based on a set of criteria given in state regulation. The species are assigned numeric risk scores of one to fifteen, which can be summarized as low (1-8), medium (9-12), or high (13-15), and a proposed letter rating of A, B, C, or D. Those ratings then go through an internal and public review process. If approved, the plants are then classified using the official letter ratings, with a rating of C implying that the species is of limited concern or very widespread and D implying that the species is considered beneficial rather than harmful. The rating system is fairly recent, and new species continue to be introduced into the state, so not all species that could be considered noxious weeds in the state have been rated and only a portion of the species that have been rated are officially listed as California noxious weeds. The ratings assist land managers and County Agriculture Commissions in making decisions about those species that may pose a problem in their locations.
Noxious weed seeds are classified by regulation as either Prohibited, meaning they cannot be sold or used in the State, or as Restricted, with tolerances limits set for the amount of seed allowed in agricultural seed offered for sale in the state, following the provisions of the Federal Seed Act. Vegetable seeds offered for sale are not currently subject to the same labeling requirements as agricultural seeds such as those from grasses, forages, and oilseeds, but vegetable seed lots of more than 1 pound in interstate commerce are now subject to noxious weed labeling in the 2020 update of the Federal Seed Act.
Refer to my interview with Doug Johnson for an explanation of the separate list of invasive plants developed by the California Invasive Plant Council (Cal-IPC). That list, which emphasizes invasive plant species in natural habitats, includes a number of plants not on the official State list of noxious weeds.
I asked Bob about the fact that some species on the California list are native plants. By current State regulations, native species can be included, but current practice is only to list native plant species as noxious under unusual circumstances. For example, native species of dodder (Cuscuta) are included on the California noxious weed list and rated C because certain of these species are economically significant stem parasites that attack crop species and garden plants and these species can be subject to various forms of control. Native species that are not on the State noxious weed list are normally considered beneficial/native, meaning that no official control actions are applied. California regulations recommend that the designation of species as noxious weeds should not be detrimental to the agriculture of the state, as broadly defined to include forestry and horticulture, but some introduced horticultural plants can be invasive in the state and then are subject to rating and possible listing as noxious weeds. The Cal-IPC list does also includes some horticultural and some agricultural species that have become invasive.
I also asked Bob which online database is best to use, for the latest information on the distribution and the most accurate authority on scientific names for plant species. The advent of inexpensive and easy to use DNA analysis in coordination with traditional taxonomic studies has resulted in significant numbers of changes to species classifications in recent years. He said that the most up-to-date database for scientific names is the USDA National Plant Germplasm System, Germplasm Resources Information Network (USDA GRIN) database.
The GRIN database is used by official seed analysts in the United States and Canada (and the USDA APHIS) as the official source for taxonomy and nomenclature of scientific names and their authorities (and placement in families). The database includes many agricultural and horticultural and weedy plants and some native plants from around the world. It is not an official source for common names, but does provide some common names along with synonymous scientific names, geographic distributional information at the whole state level, and literature references.
A number of databases provide useful information on geographic distribution of weedy plants in North America. The USDA PLANTS database provides detailed distribution maps usually resolved to the county level, widely used common names, and photographic images, but for seed analysts it isn’t the official source of scientific names. The distribution maps from the EDDMapS database from the University of Georgia Center for Invasive Species and Ecosystem Health are also particularly useful across the United States, and the Calflora database and Consortium of California Herbaria provide detailed distributional information for weeds and native plants within California.
He also said that the USDA maintains an online All-States Noxious Weed Seed List that provides information on noxious weed seed species designated in each of the States. That list is managed by the UDSA Agricultural Marketing Service in Gastonia, North Carolina. They update the scientific names in that list regularly.
I asked Bob, via email, about the classification of three closely related knapweed species: Are Centaurea nigra & C. nigrescens now considered subspecies of C. jacea?
His answer is enlightening as it helps us understand the complexities of identifying closely related invasive species that, in their new environment, have come into close contact and are now regularly hybridizing.
Bob wrote: “Depending on how broadly or narrowly one wants to delimit the species in this complex group, different floras have treated these Eurasian species more narrowly or more broadly. The Flora of North America treatment (Keil and Ochsmann, 2006, 19: 181-194) recognizes C. jacea L. (brown-ray knapweed), C. nigra L. (black knapweed), and C. nigrescens Willd. (Tyrol knapweed) as separate species, as is also done by the 2nd edition of the Flora of the Pacific Northwest (Giblin et al., eds., 2018), and the earlier treatment in the Flora Europaea (Tutin et al., eds., 1976). The treatment in the Jepson Manual of the Flora of California (Keil, 2012) treats C. nigra as a subspecies of C. jacea [C. jacea subsp. nigra (L.) Bonnier & Layens]] reflecting the observation that very variable populations in northern California [C. x moncktonii C. E. Britton, etc.] are apparently derived from hybridization between C. jacea and C. nigra. The 2012 Jepson Manual treatment indicated that as of that time C. nigrescens was not considered to be naturalized in California.
“So, wearing my hat as a seed analyst, I would personally follow USDA GRIN and recognize three species, but realize that a lot of plants in the field in California may not easily fit into C. nigra and C. jacea because they are apparent hybrid derivatives. The treatment used for the California noxious weed list (CCR 4500) more or less follows from the treatment in the Jepson Manual and by its synonymy indicates that all of these taxa [C. jacea L., C. nigra L., C. nigrescens Willd., and by extension any hybrids thereof] are treated as noxious weeds in California. We may eventually update our various official lists in regulation to reflect the USDA/GRIN taxonomy, but in practice we would rate all of them as noxious weeds, particularly given that many individual plants in California will only be able to be identified as belonging to the complex species group.”
More California Interviews:
Interview with Dr. Robert Price, California Department of Food and Agriculture
Email: robert.price@cdfa.ca.gov Work phone: 916-738-6700
Interview by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western
(Interview reviewed & approved Sept. 29, 2020)
I had a telephone interview with Dr. Robert Price in September, 2020. Dr. Price works for the Plant Pest Diagnostics Branch of the California Department of Food and Agriculture (CDFA) as a Senior Seed Botanist/Specialist. He is also the CDFA Primary State Botanist. He is a certified seed analyst and a plant taxonomist.
Dr. Price provided information to assist me in sorting out the various lists of noxious weeds and invasive plants in California. There is an official State list of “noxious weeds” listed in the California Code of Regulations (CCR 4500).
Many of the plants on that the official list have also been classified, using the State’s official Pest Risk Proposal rating system. Each species subject to analysis as a possible noxious weed species is rated based on a set of criteria given in state regulation. The species are assigned numeric risk scores of one to fifteen, which can be summarized as low (1-8), medium (9-12), or high (13-15), and a proposed letter rating of A, B, C, or D. Those ratings then go through an internal and public review process. If approved, the plants are then classified using the official letter ratings, with a rating of C implying that the species is of limited concern or very widespread and D implying that the species is considered beneficial rather than harmful. The rating system is fairly recent, and new species continue to be introduced into the state, so not all species that could be considered noxious weeds in the state have been rated and only a portion of the species that have been rated are officially listed as California noxious weeds. The ratings assist land managers and County Agriculture Commissions in making decisions about those species that may pose a problem in their locations.
Noxious weed seeds are classified by regulation as either Prohibited, meaning they cannot be sold or used in the State, or as Restricted, with tolerances limits set for the amount of seed allowed in agricultural seed offered for sale in the state, following the provisions of the Federal Seed Act. Vegetable seeds offered for sale are not currently subject to the same labeling requirements as agricultural seeds such as those from grasses, forages, and oilseeds, but vegetable seed lots of more than 1 pound in interstate commerce are now subject to noxious weed labeling in the 2020 update of the Federal Seed Act.
Refer to my interview with Doug Johnson for an explanation of the separate list of invasive plants developed by the California Invasive Plant Council (Cal-IPC). That list, which emphasizes invasive plant species in natural habitats, includes a number of plants not on the official State list of noxious weeds.
I asked Bob about the fact that some species on the California list are native plants. By current State regulations, native species can be included, but current practice is only to list native plant species as noxious under unusual circumstances. For example, native species of dodder (Cuscuta) are included on the California noxious weed list and rated C because certain of these species are economically significant stem parasites that attack crop species and garden plants and these species can be subject to various forms of control. Native species that are not on the State noxious weed list are normally considered beneficial/native, meaning that no official control actions are applied. California regulations recommend that the designation of species as noxious weeds should not be detrimental to the agriculture of the state, as broadly defined to include forestry and horticulture, but some introduced horticultural plants can be invasive in the state and then are subject to rating and possible listing as noxious weeds. The Cal-IPC list does also includes some horticultural and some agricultural species that have become invasive.
I also asked Bob which online database is best to use, for the latest information on the distribution and the most accurate authority on scientific names for plant species. The advent of inexpensive and easy to use DNA analysis in coordination with traditional taxonomic studies has resulted in significant numbers of changes to species classifications in recent years. He said that the most up-to-date database for scientific names is the USDA National Plant Germplasm System, Germplasm Resources Information Network (USDA GRIN) database.
The GRIN database is used by official seed analysts in the United States and Canada (and the USDA APHIS) as the official source for taxonomy and nomenclature of scientific names and their authorities (and placement in families). The database includes many agricultural and horticultural and weedy plants and some native plants from around the world. It is not an official source for common names, but does provide some common names along with synonymous scientific names, geographic distributional information at the whole state level, and literature references.
A number of databases provide useful information on geographic distribution of weedy plants in North America. The USDA PLANTS database provides detailed distribution maps usually resolved to the county level, widely used common names, and photographic images, but for seed analysts it isn’t the official source of scientific names. The distribution maps from the EDDMapS database from the University of Georgia Center for Invasive Species and Ecosystem Health are also particularly useful across the United States, and the Calflora database and Consortium of California Herbaria provide detailed distributional information for weeds and native plants within California.
He also said that the USDA maintains an online All-States Noxious Weed Seed List that provides information on noxious weed seed species designated in each of the States. That list is managed by the UDSA Agricultural Marketing Service in Gastonia, North Carolina. They update the scientific names in that list regularly.
I asked Bob, via email, about the classification of three closely related knapweed species: Are Centaurea nigra & C. nigrescens now considered subspecies of C. jacea?
His answer is enlightening as it helps us understand the complexities of identifying closely related invasive species that, in their new environment, have come into close contact and are now regularly hybridizing.
Bob wrote: “Depending on how broadly or narrowly one wants to delimit the species in this complex group, different floras have treated these Eurasian species more narrowly or more broadly. The Flora of North America treatment (Keil and Ochsmann, 2006, 19: 181-194) recognizes C. jacea L. (brown-ray knapweed), C. nigra L. (black knapweed), and C. nigrescens Willd. (Tyrol knapweed) as separate species, as is also done by the 2nd edition of the Flora of the Pacific Northwest (Giblin et al., eds., 2018), and the earlier treatment in the Flora Europaea (Tutin et al., eds., 1976). The treatment in the Jepson Manual of the Flora of California (Keil, 2012) treats C. nigra as a subspecies of C. jacea [C. jacea subsp. nigra (L.) Bonnier & Layens]] reflecting the observation that very variable populations in northern California [C. x moncktonii C. E. Britton, etc.] are apparently derived from hybridization between C. jacea and C. nigra. The 2012 Jepson Manual treatment indicated that as of that time C. nigrescens was not considered to be naturalized in California.
“So, wearing my hat as a seed analyst, I would personally follow USDA GRIN and recognize three species, but realize that a lot of plants in the field in California may not easily fit into C. nigra and C. jacea because they are apparent hybrid derivatives. The treatment used for the California noxious weed list (CCR 4500) more or less follows from the treatment in the Jepson Manual and by its synonymy indicates that all of these taxa [C. jacea L., C. nigra L., C. nigrescens Willd., and by extension any hybrids thereof] are treated as noxious weeds in California. We may eventually update our various official lists in regulation to reflect the USDA/GRIN taxonomy, but in practice we would rate all of them as noxious weeds, particularly given that many individual plants in California will only be able to be identified as belonging to the complex species group.”
More California Interviews: