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The rich soils and moderate climate of Monterey County make it an
ideal place for invasive weed species to colonize. By definition, weeds
are plants out of place, meaning that they grow in areas where they are
not wanted. Weeds are usually able to out-compete local native plant
species for water and space because they are more prolific, have more
vigorous growth, and lack predators that would otherwise help to keep
them in check. They also degrade habitat for other wildlife, domestic
animals, recreation, and other land use activities. The agricultural
industry is particularly affected by weeds; their control expense is
ultimately passed on to the consumer. Weeds affect everyone, either
directly or indirectly.
We are continually being threatened by the introduction of new weed
species that have the potential to become widespread serious problems.
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:
diffuse knapweed, spotted knapweed, biddy-biddy, and hydrilla, (all
State “A”-rated species).
However, a number of invasive noxious weeds have invaded the County
and have reached levels that are beyond hopes of eradication. Most of
these are still expanding into new areas, and thus it is important that
some efforts be made to halt their spread. Efforts to control these
weeds are focused on trying to keep them under manageable levels in
areas where they occur and to eliminate them from or keep them out of
localized areas.
There is some debate about which noxious weeds are the most
significant or invasive. The following are among the most prevalent
weeds in Monterey County:
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Fertile Capeweed (Arctotheca calendula)- Fertile
capeweed was detected in May, 1999, west of Escolle Road near Gonzales.
It is a native of South Africa and has colonized large areas of
Australia. Fertile capeweed occurs in only a couple of other locations
in the state in Humboldt and Marin Counties, and is rated as an
"A" species by the State Department of Food and Agriculture
(which means it is subject to mandatory eradication where ever it is
found). It has been associated with subterranean clover seed from
Australia. The source of the infestation here is not known.
Fertile capeweed plants initially form rosettes, and under ideal
conditions, develop into low plants up to about 6 inches high and 16
inches across. When the plants dry, dense mats of seed surround them.
The seed-producing form, i.e. fertile, is considered to be an annual.
Aside from the production of seeds (which are enclosed in pinkish-brown
balls of long hairs), it is differentiated from sterile form by it's
non-creeping growth habit and having flowers with dark purple to black
centers-the sterile form has flowers of uniform yellow.
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French
Broom ( Genista monspessulana) is an invasive woody
shrub-like plant which is native to the Canary Islands. It is a member
of the pea family and grows up to 9 ft. in height. During the spring it
is covered with profuse yellow blooms about a half-inch long. It is
found primarily along the coast and northern Monterey County. French
broom is a prolific seeder and in some areas, seedlings will appear to
carpet the ground. Fortunately it is shallow rooter and can be easily
removed by pulling. In many areas, especially along roadways, it had
become the dominant shrub. A related invasive plant, Scotch broom,
Cytisus scoparius, has similar habits. French broom is relatively easy
to control by flaming or herbicide treatments of seedlings. When the
ground is moist, entire large plants can be pulled up by their roots using
a weed wrench. Once a treatment program is started, it is important to
maintain control efforts, as the French broom seeds will germinate for
several years. Find out more at some of these
sites:
Wildland Invasive Species Team (UC Davis) - Archived
Content Only
California Invasive Plant
Council (Cal-IPC)
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Cape Ivy
( Delairia odorata), also known as German Ivy ( Senecio
milkanioides) is a member of the sunflower family with
bright green leaves shaped somewhat like ivy. The flowers are small and
yellow and occur in dense clusters. It is an invader from South Africa that has become or is
rapidly becoming an ecological disaster in most of the riparian or
stream-side areas of the County, especially along the coast. This plant
is capable of forming a dense vine-like growth that completely smothers
all underlying vegetation. It is very difficult to control without
destroying any and all associated plants along with it. Any small root
fragments left unkilled are capable of regrowth. Currently, USDA
researchers are investigating a number of bio-control agents in Africa
that may be introduced here in the future. Check these links for
information about this serious pest:
National
Park Service
California
Forest Stewardship Program on Cape Ivy
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Arundo, Giant Reed ( Arundo donax) - This invasive weed, native
to North Africa, is becoming a dominant plant along the Salinas River,
where it is crowding out native species. It has the potential for
becoming established in other habitats near fresh water. Arundo is
spread by the breaking up and movement of root fragments. Where it
occurs in a river, it can restrict stream flow and enhance flooding.
Team
Arundo Del Norte
UC
Davis on Arundo Donax
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Pampas grass-type species, include pampas grass,
(Cortaderia selloana) and purple pampas grass (Cortaderia jubata) - Both these are native to
South America and are similar in appearance, although purple pampas
grass is
considered to be the more invasive, and is the species most commonly
seen in this area. These grasses form large clumps of tough wiry and
sharp-edged leaf blades that are difficult to remove once they reach a
certain size. It has the potential for prolific seed production, and
does so by asexual means (all flowers are female). Most purple pampas
grass infestations are seen along the coastal areas, although true pampas
grass , Cortaderia selloana is available in the nursery trade and plants
have been widely planted. It was thought that the true pampas grass was
safe, because it required male plants to pollinate, and supposedly none of
the plants being sold were male. In fact, male plants are now being found
in the wild. In the past, this grass was recommended for use as an erosion
control, especially where road cuts had been made. It has unfortunately
proven to be a serious threat to native plant habitat by it's
invasiveness. For more information,
visit here:
Landowners Guide to Native Grass Enhancement
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Yellowstar-thistle (Centaurea solstitialis)
is unquestionably the most serious rangeland noxious weed in the
County. As its name implies, the flower of this plant is yellow, and
is armed around the base with long sharp spines. The rest of the
plant, including stems and leaves are spineless. Mature
start-thistle plants can grow over 3 feet tall and 3 ft. across
under ideal conditions. It is able to colonize different areas by
having a deep root system and an adaptable growth form, both tall
and slender in grassy areas, or broad and bushy in less competitive
situations. It has developed extensive infestations in the State as
well, mostly in northern areas. Yellow star-thistle is a very
adaptable plant and is quite successful at out-competing native
plants. In some areas, it forms almost impenetrable stands that are
so thick the even it cannot grow again for awhile. Fortunately, a
number of introduced bio-control agents have been released here
against it which are becoming established and thriving. Some of
these agents are being made available for redistribution in the
County. For more information, contact our office at 831-759-7325.
Additional information can be found here:
University of California Statewide Integrated Pest Management
Program
Wildland Invasive Species Team - Archived Content
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Veldt
Grass (Ehrharta calycina) is
native to southern Africa. It was introduced to Davis, California as a
drought-resistant grass for rangelands, but it was unable to withstand
heavy grazing. It is now common on the coastal sand dunes at San Luis
Obispo and San Diego. It flowers in the spring. The leafy stems reach to 3
feet in height and are adapted to light sandy soils. Veldt grass occurs in
several locations in Monterey County near the ocean. It can form dense
stands and crowds out native vegetation. A heavy infestation can be seen
at the intersection of Del Monte Rd. and Lapis Rd. near Marina. For more
information, visit:
Cal
Photos-Berkeley Digital Library Project
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Taurian Thistle (Onopordum tauricum) - Taurian
thistle is another weed on the State's "A" list. It is a large
thistle, capable of growing up to 8 ft. tall under ideal conditions.
Mature plants have been found in very dry years that were only a few
inches tall, but with a fully developed small seed head. The flowers are
purple-red, and are surrounded by numerous pointed bracts. The leaves are
spiny along their edges, and the stems have spiny wings up their entire
length. Taurian thistle was first found in 1973 on rangeland along Paraiso
Springs Rd. near Soledad. In subsequent surveys it was found at Paraiso
Hot Springs and down the drainage creeks from there all the way to Arroyo
Seco Rd. The plants are found scattered along the drainage, but usually in
the same general locations where plants were found in previous years. The
Taurian thistle seeds are capable of long dormancy, usually being
stimulated to germinate by scarification or scratching of the seedcoat.
This has be seen noted on a couple of occasions near the resort, when the
lower meadow was disced, stimulating the development of plants in areas
where they had not been seen for many years. This process is suspected to
play a role when seeds are moved along with sand in water. Eradication
treatments are made on Taurian thistle two times a year. Treatments are
made by shovel and backpack sprayer, using Roundup and Transline. Plants
gone to seed have their seed heads clipped and bagged, to be disposed of
later. The entire drainage creek from Paraiso Hot Springs to Arroyo Seco
Road is surveyed, mostly by foot. For more information, visit:
CDFA
on Taurian Thistle
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Puna Grass (Achnatherum
brachychaetum) - This grass is native to the Andes
regions of South America, where it forms dense stands covering large
areas. Under ideal conditions, it can grow up to 3 ft. tall, and 3 ft.
across. The plants have tough fibrous roots, but no creeping rhizomes. It
is unusual in that it forms seeds at the base of the plant within the
stems, so-called cleistogamous seeds. These are in addition to the more
usual seeds formed in florets at the tops of the stalks. The cleistogamous
seeds are capable of propagating the plants even if the tops are cut back
or mown. One of the clues to identifying clumps of suspect grass as puna
grass is by dropping ones open palm down on the tips of the blades. Puna
grass blades have sharp points and will feel prickly.
Puna grass was detected in 1995 in a pasture in Greenfield. Subsequent
surveys revealed the weed at 10 locations in Greenfield, one location
along Hwy 101 in Soledad, and along San Vicente Rd. in Soledad in an old
vineyard. Most of the finds were in permanent pastures, the heaviest being
along Third Ave., where 5 acres of pasture are heavily infested. It is
another State "A"-rated weed, and occurs on only a few other
locations in California.
Treatments are made 4 times a year, with shovels being used in pastures
with livestock, or by backpack sprayers using Roundup where animals can be
moved off for a few weeks, or in non-crop areas. Some experimental
treatments were also done with propane burners, which did not give
acceptable control. The burner did kill the grass, but required an
unacceptable amount of time per plant. The puna grass seed has a very long
viability and thus will probably be giving rise to plants for several
years after we began treatments. Grass that we are treating now is
probably arising from such dormant seed. For more information, visit:
CDFA
on Puna Grass
Cal
Photos-Berkeley Digital Library Project |
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Contact us
about Weeds
Visit
the California Department of Food and Agriculture's web site.
This link will take you to their Noxious Weeds section.
Weeds considered to be eradicated in Monterey County:
BIDDY-BIDDY (Acaena novae-zelandiae) was 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.
DALMATIAN TOADFLAX (Linaria genestifolia) was 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. The
caretaker had also been educated about the rating of the weed and has
removed it when found. Subsequent visits to the area over the past
several years have failed to reveal any sign of the weed. In 1974,
County staff detected an infestation of Dalmatian Toadflax along the
railroad between Salinas and Castroville, just north of Cooper Rd. The
infestation was treated using Tordon from a backpack sprayer.
The following year, additional plants were found and treated.
Also, in 1974, a single Dalmatian toadflax plant was found by County
staff (Bill Nutley) near the Gould Ranch along Arroyo Seco Rd. The plant
was removed by shovel. In 1976, a small infestation of Dalmatian toadflax was found by County
staff along the railroad a mile south of Gonzales. It was treated with
Tordon. In 1978, a couple of individual Dalmatian toadflax plants were
found growing in the ballast between the main line railroad tracks
one-half mile south of Castroville. They were hand pulled. In 1992,
while doing a site inspection for a post-entry permit at a residence in
Carmel Valley, County staff noted some Dalmatian toadflax plants growing
in the resident's garden. The resident was advised of the
noxious nature of the plant, and treated these with Roundup. He thought
he might have obtained the plants from the UC Santa Cruz Arboretum,
which they vigorously denied. Unfortunately, the resident indicated that he
had allowed a number of unspecified people to take starts from the
toadflax plants. Subsequent visits to all the above locations have
failed to reveal regrowth of the weed.
PLUMELESS THISTLE (Carduus acanthoides) was 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. Subsequent surveys failed to
detect additional thistles. At about this same time, there were reports
of Canary grass seed being contaminated with plumeless thistle seed.
Some of this suspect seed had been seeded by airplane around Garland
Ranch Park, but surveys done around the park have failed to detect any
thistles.
HYDRILLA (Hydrilla verticillata) was 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 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. The source of
the Hydrilla was thought to have been from contaminated plant material
originating in Florida.
SPOTTED KNAPWEED (Centaurea maculosa) was 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.
DIFFUSE KNAPWEED (Centaurea diffusa) was detected by County staff in
1988 while doing an entryway survey with the State biologist on Hwy 101
between San Lucas and San Ardo. The infestation was located at the 27
mile post on the northbound side of the freeway where a power line
crosses the road, and consisted of several mature plants. Delimiting
surveys determined that the infestation was limited to this 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.
Where to Have Weeds Identified by Trained Botanists Proper Weed
Identification is Key to a Successful Program
The Situation: An odd looking plant is found growing on the side
of the road, on a back-country trail, or in a newly constructed site.
What is the plant? Where can you go to have it identified? Some people
might rely on photo-based field guides such as "Weeds of the
West," while the more ambitious might attempt keying out a given
species with the "floristic bible", The Jepson Manual. Given
the vast diversity of California's flora, this task can be daunting. The
alternative would be to send a sample in for identification by a trained
botanist.
Importance of proper identification: Informed management
decisions rely heavily on what species or species compositions
are present. Species specific characters such as: life cycle (annual or
perennial), reproductive mode (seed, vegetative parts), and growth form
are critical in assigning appropriate control and restoration
treatments. Time and again, situations exemplifying the importance of
having a weed professionally identified present themselves. Trained
Botanists and Taxonomists have access to libraries of specimens
(herbaria) and experience using them both properly and effectively.
Where to go?
Many established weed identification sites are available throughout the
state. The following list of professional plant taxonomists is a great
resource when compiling a species inventory in your county, at your
preserve, or on your property.
County Agricultural Commissioner's Office
Ag Commissioners' responsibilities include carrying out countywide
programs for both pest detection and weed & vertebrate pest
management. All counties throughout the state have biologists that are
knowledgeable in local invasive and noxious weed identification and
control. County biologists send samples on to the CDFA Pest Diagnostic
Lab for I.D. confirmation.
Contact the Monterey County Ag
Commissioner's office about weeds
Farm Advisor’s Office
Through University of California Cooperative Extension a network of
farm advisors extends throughout the state. Farm advisors work with
farmers, processors, and other agricultural operators, as well as local
governments, regulators, and the environmental community. Counties have
both crop and non-crop farm advisor specialists trained in a wide array
of fields, including weed identification and management. Farm Advisors
send samples to the UC Davis Herbarium for I.D. confirmation.
To find a Farm Advisor near you, http://www.cdfa.ca.gov/counties/
California Department of Food and Agriculture, Plant Pest
Diagnostics Branch
California Department of Food and Agriculture, Plant Pest
Diagnostics Branch Taxonomists at the Plant Pest Diagnostics Branch are
mandated to identify pest plants sent in by CDFA and County Biologists.
Plant identification is an integral part of weed pest exclusion,
detection, control, and eradication. Seventy-five percent of the
counties submit 90% or more of their plant specimens to the Botany
Laboratory for identification or confirmation. The ability of the
laboratory to assist field programs promptly and accurately has aided in
pinpointing the distribution of the major weed pests in the State. In
1998, the Botany Laboratory made 1,323 plant identifications and
provided more than 500 consultations.
Contact: CDFA Senior Plant Systematist, Fred Hrusa, fhrusa@cdfa.ca.gov
UC Davis Herbarium
Taxonomists at the UC Davis Herbarium are mandated to identify
[pest] plants sent in by UC Cooperative Extension and University
researchers. They also perform this service for the general public. The
identification of small lots of specimens is done free of charge; for
larger lots, there is charge per identification. Any member of the
public may consult the herbarium's plant collections, library, and slide
collection. During the 1998-99 fiscal year, herbarium staff performed
over 500 plant identifications, filled over 200 information requests,
and welcomed over 700 visitors. Most off-campus users, including UC
Cooperative Extension farm advisors, consult the herbarium by phone,
mail, or email.
Contact: UCD Herbarium Curator, Ellen Dean, (530) 752-1091, eadean@ucdavis.edu
A Local University, Botanical Garden, or Herbarium Near You
There are many locations throughout the state where professionally
trained botanists/taxonomists can make identifications. However, these
identifications are made on more of a voluntary basis and therefore
availability of site I.D. will vary pending staffing and resources.
Locations include herbaria and facilities at Universities, State
Universities; and Botanical Gardens (UC Riverside, UC Berkeley, Chico
state, Humboldt, Santa Barbara Botanical Garden, Cal State Stanislaus,
Fresno State, among others).
Contact us
about Weeds 
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