CDFA “A” Rated Weeds Considered Eradicated from County

We are continually being threatened by the introduction of new weed species, once a weed had reached a certain level of infestation, eradication becomes difficult or impossible. The goal of an exclusion program is to detect the introduction of a weed or other potentially harmful species before it reached unmanageable populations. A number of noxious weeds have been detected under this program and successfully eradicated:

• Biddy-Biddy Acaena novae-zelandiae
• Dalmatian Toadflax Linaria genistifolia
• Plumeless Thistle Carduus acanthoides
• Hydrilla Hydrilla verticillata
• Spotted Knapweed Centaurea maculosa
• Diffuse Knapweed Centaurea diffusa

Biddy-Biddy Acaena novae-zelandiae

• First found in 1954 in the Carmel Highlands area, where it was noted to be in patches up to 3 ft. across.
• By 1966, eradicative treatments had reduced the infestation to only 3 plants. Since that time, surveys have failed to detect any more plants.
• A recent report of Biddy-Biddy being found near Bixby Bridge on Hwy 1 was checked out; surveys at this site also failed to reveal any plants.

CalIPC plant profile – Acaena novae-zelandiae

Dalmatian Toadflax Linaria genistifolia

• Noted in 1964 at the Carmel Mission infesting a portion of the Cemetery.
• No concerted effort was made to eradicate it until 1980; when County staff visited the Mission and noted the infestation still there. Since that time, regular visits to the Mission have been made to mechanically control the toadflax--use of chemicals was not permitted by the Mission.
• Over the years there have been several sightings of the weed in different locations of the County. In each instance, the plant or group of plants was removed by methods including Tordon, RoundUp, use of a shovel, and hand pulling

CalIPC plant profile – Linaria dalmatica ssp. dalmatica

Plumeless Thistle Carduus acanthoides

• Reported to our office by a resident (Ewoldson) near Big Sur in 1976. Mrs. Ewoldson, who was a botanist, recognized the thistle as being something out of the ordinary.
• County and State personnel found several plants at this location in a small area; they were eradicated by shovel. It was speculated that the thistles may have been brought in with hay.
• There were reports of Canary grass seed being contaminated with Plumeless Thistle seed around Garland Ranch Park, but surveys done around the park have failed to detect any thistles.

CalIPC plant profile – Carduus acanthoides

Hydrilla Hydrilla verticillata

• Tracked down to an aquatic nursery along Schulte Rd. in Carmel Valley in 1978 after a shipment of plants were found contaminated with the weed. The shipment was thought to have originated in Florida.
• The source of the infestation was found to be one small pond, about 5 ft. by 10 ft. The pond was drained and plant material removed.
• Subsequent surveys of the aquatic gardens failed to detect any addition Hydrilla.

CalIPC plant profile – Hydrilla verticillata

Spotted Knapweed Centaurea maculosa

• Found by County staff along San Benancio Rd. in 1978, while doing an entryway survey. A couple of rosettes of the weed were stumbled upon on the shoulder of the road while sweeping the vegetation for insects. The plants were dug out by shovel.
• Surveys of the immediate area failed to detect additional plants and subsequent surveys were negative.
• It is speculated that the seeds may have blown off a vehicle carrying hay, livestock, or beehives from a contaminated area.
• In 1999, a single plant was detected by BLM staff at Ft. Ord. along Barloy Cyn. Rd. near the Merrill Ranch. The plant was removed. This find may be evidence that an as yet undetected infestation of spotted knapweed might exist in the Corral de Tierra-Ft. Ord area.

CalIPC plant profile – Centaurea stoebe ssp. micranthos

Diffuse Knapweed Centaurea diffusa

• Detected by County staff in 1988 while doing an entryway survey with a State biologist on Hwy 101 between San Lucas and San Ardo.
• Delimiting surveys determined that the infestation was limited to one side of the highway, extending for a distance of about 100 ft. The plants were treated with herbicide.
• For the next several years, new plants were shoveled out or treated with Roundup. After several additional years of surveys were made with negative findings, the infestation was declared to be eradicated.

CalIPC plant profile – Centaurea diffusa