fight against Pierces Disease (PD) in Temecula has benefitted
the entire California wine industry. The scientific struggle to
find information and solutions for the disease employs scores
of researchers and millions of dollars all because the tiny (2,500-acre)
grapegrowing community in Temecula mounted a conscious and concentrated
effort to focus attention on the problem.
A look at Temecula vineyards
Driving east on Rancho California Road from Highway 15, one travels
through about four miles of the boomtown known as Temecula, shiny
new shopping malls alternating with crisp housing developments
along a wide, pleasant thoroughfare. The sparkling new city ends
abruptly at Butterfield Stage Road where Temecula wine country
Temecula grapevines enjoy wider spacing than is common these days
in North Coast vineyards. Some vertical trellising exists, but
mostly there are lots of low, healthy vines in orderly rows among
citrus groves. The sandy, tan-gray soil shows between widely spaced,
lush, green vines. At mid-day, with the temperature in the mid-80s,
and the air redolent of lemons, the atmosphere is serene Southern
California wine country.
This does not appear to be the waste land one would expect from
recent wine trade publication reports. Several reports said fall
would be when the devastation wrought by Pierces disease
would be most evident.
Where were the massive symptoms predicted? You would expect mists
of sharpshooter rain wafting out of citrus groves, and exposed
trellises covered with decayed, withered vines, raisined grapes
beneath chlorotic and necrotic red and yellow leaves, petioles
bare of leaf blades, like skeletal fingers from lignified canes.
A closer look than just driving past vineyards shows that all
is not well. There are skips, rows where one, five, seven, 10
vines, or a whole row are missing. Vines sporting scorched leaves,
persistent petioles, and canes with uneven wood maturation mark
Pierces disease. Some of the enormity of the problem creeps
upon you like a bad dream. The clean empty fields are not just
unplanted land: they are former vineyards, ripped out.
Scars left by earth-moving equipment appear fresh upon the sandy
earth. Mount Palomar Winery has the equipment pushing dirt around
in the area between the winery and Rancho California Road, where
both vines and citrus trees used to grow. Growers have become
scrupulous about not retaining any infected vines. Pierces
disease spreads when a sharpshooter feeds on the infected vines
and then spreads the bacterial pathogen Xylella Fastidiosa that
causes the disease to healthy vines.
Nature and extent of the
Driving up the driveway to Callaway Coastal Winery and mounting
the low hill the winery sits upon, the extent of the Pierces
disease damage becomes even more apparent. As you crest the hill,
the hill beyond comes into view, where large skips are visible.
To the east, whole blocks gape in silent witness where the vines
have been ripped out.
Callaways home vineyard is among the hardest hit. The devastation
lies adjacent to the Callaway tasting room parking lot, right
below Allies at Callaway Winery restaurant.
Vineyard manager, Craig Weaver, has managed Callaway vineyard
operations for 18 years. He has watched glassy-winged sharpshooters
spread Pierces disease, and he has since helped the winery
Partly in reaction to the damage wrought by PD, Callaway Vineyards
& Winery has become Callaway Coastal Winery. It now sources
50% of its grapes from Santa Barbara, San Luis Obispo, and Monterey
Adjacent to the Callaway Winery are home vineyards that have sustained
40% damage: about 270 of the 675 acres of grapes are gone.
Several miles away from the home vineyard lies the Bell Vineyard,
owned by Callaway. Its slightly resistant varietals and distance
from citrus trees make it less prone to PD. Syrah vines on SO4
rootstock are surviving, along with Chardonnay on Riesling roots
next to a lemon grove.
Vines at Callaway have almost all been budded over at least once.
Varietals are grafted onto varietals: Merlot on Sauvignon Blanc,
Chardonnay on White Riesling, Mourvédere on Sauvignon Blanc,
Dolcetto on Chenin Blanc, Nebbiolo on Chenin Blanc, Chardonnay
on White Riesling.
All these changed varietals reflect changes in the winerys
marketing plans, not which varietals have the best resistance
to Pierces disease. The different varietals grafted onto
varietals make for an interesting lesson. It is the original or
base vine that is the critical factor. Chenin Blanc and White
Riesling are among the most tolerant.
Where Merlot is grafted onto Sauvignon Blanc, the vines are hit
pretty hard, not because of the Merlot, which is fairly resistant
to PD, but because it is on Sauvignon Blanc roots, which are very
susceptible. The three varietal combinations that have survived
surprisingly well are Dolcetto on Chenin Blanc, Nebbiolo on Chenin
Blanc, and Chardonnay on White Riesling.
The vulnerability of Sauvignon Blanc and Chardonnay has been difficult,
since Temeculas reputation, and Callaways even more
so, began with white wine. Chardonnay and Sauvignon Blanc are
among the most heavily planted varieties.
Proximity to and type of citrus
Much of the research and speculation about the spread of Pierces
disease in the Temecula area focuses on the issue of proximity
to citrus. The area is one of the few in California where commercial
citrus and vines co-exist. Glassy-winged sharpshooters tend to
reach great numbers in the citrus, where they do little damage
before moving out into adjacent vineyards where they wreak havoc.
Thomas M. Perring and others address this issue in a California
Agriculture article (Perring, Thomas A.; Farrar, Charles A,; Blua,
Matthew J. Proximity to citrus influences Pierces
disease in Temecula Valley vineyards.
JulyAugust, 2001 Vol. 55. Number 4 Pages 1318).
Although they found some blocks of sharpshooters in the center
of a vineyard and vines further from citrus more infected than
those on the edge and close to the groves, generally their research
indicates that infection is most severe when the vines are
adjacent to citrus, and that the damage declines as one moves
away from citrus.
Weaver adds a further practical spin on the issue. Not all citrus
is equal, or equally lovely to the insects that spread PD. Glassy-winged
sharpshooters prefer grapefruit and lemons. They do not find oranges,
tangerines, and other varieties nearly as desirable.
Weaver points to two vineyards recently planted next to citrus
groves. One next to navel oranges thrives and shows no signs of
PD. The other, next to lemons, has all the symptoms and will probably
have to be pulled out. Its the flushes, explains
Weaver. We think the glassy-winged sharpshooter (GWSS) likes
the lemon and grapefruit because they experience more growth flushes
per year. During a growth flush citrus trees put out tender new
Citrus is definitely a factor in spreading the disease to vines.
Glassy-winged sharpshooters, native to the Southeastern U.S.,
were first seen in California in 1989 in Ventura, where citrus
is plentiful, but there is very little commercial viticulture.
Glassy-winged sharpshooters were discovered in Temecula in 1996.
Admitting the problem,
getting everyone involved
Once the wine growing community in Temecula realized the problem,
they sought consensus among themselves. Being small in acres and
numbers, helped. Once the grapegrowers and wineries were united,
they sought cooperation from citrus growers.
Weaver recalls Gary McMillan, who owns or manages much of the
citrus in the Temecula area, including grapefruit on the northern
perimeter of the Callaway home vineyard, offering to help. McMillan
told Weaver, Craig, I dont want to be considered the
guy who didnt cooperate and help, thus leading to the demise
Weaver realized that was a crucial statement because McMillan
had a well-established integrated pest management (IPM) program.
Any new pesticide effort could possibly affect that program. McMillan
was willing to allow irrigation of his citrus groves with one
32 oz. per acre application of Admire as part of the program
to leave Imidacloprid to kill GWSS when feeding.
The wine industry grapegrowers in Temecula realized that they
were fighting not only a scientific and economic battle to combat
a disease with no known cure and not much research being done
on it, but also a political battle to mobilize knowledge and support
In March 1999, wine industry members asked the Temecula City Council
for a $25,000 research grant. The city responded with $125,000
and the Riverside County Board of Supervisors matched the amount.
The American Vineyard Foundation received a $250,000 research
grant for the University of California (UC) at Riverside to explore
options to control PD.
Three people emerged as part of the local leadership: Joan Sparkman,
vice president of Temecula Valley Bank and a local civic leader,
Weaver, and Ben Drake, an agriculturist who manages vineyards
in the Temecula area but also farms citrus and avocados. They
contacted the UC Cooperative Extension, FDA, UC Riverside, the
Farm Bureau, supervisors, state legislators, and local congressmen.
Drake and Weaver credit Sparkman with making a difference in the
political fight. We were just two farmers who wanted a solution,
recalls Weaver. Sparkman had the connections and was not
afraid to use them. She enlisted the aid of Riverside County
Assemblyman Rod Pacheco, who was able to mobilize support in the
State Assembly and obtain $750,000 for three years for research.
Because he grew both grapes and citrus, Drake served as a bridge
between two communities, which had different interests. Weaver,
Sparkman, Drake, and others in the community were instrumental
in creating an awareness around the state that Pierces disease
and the GWSS posed a major threat to the grape and wine industry
and the states economy.
In August 1999, culminating years of behind-the-scenes work, California
Department of Food and Agriculture (CDFA) secretary Bill Lyons
completed appointment of the CDFA GWSS/PD Task Force. The task
force met for the first time at Callaway, shortly thereafter.
Legislators attended, including Senator David Kelley, Assembly
members Rod Pacheco and Bruce Thompson, and representatives from
agriculture committees of both houses and the offices of Senator
Wes Chesbro, Senator Raymond Haynes, and Congressman Ken Calvert.
Drake and Weaver are members of the task force.
Out of this meeting and countless others, the wine industry became
aware of the problem and the legislature focused funds on research.
It took Temecula growers a few years to learn that the huge infestation
of bugs represented a new vector for an incurable disease, but
through their efforts, the rest of the state was made well aware
of the problem. A total of $10 million has since been funneled
into research for a cure.
More money has recently been made available to pay grapegrowers
for vine losses. In March 2002, the CDFA announced implementation
of a Grapevine Loss Assistance Program. This program gives money
to up to 370 grapegrowers in the four worst hit counties (Kern,
Riverside, San Diego, and Ventura) to compensate for documented
losses due to GWSS-spread Pierces disease. Up to $7.14 million
were made available for this program. Provisions of the program
were contained in Assembly Bill 1242 authored by Assembly Member
Patricia Wiggins (D-Santa Rosa).
Growers had to document up to 30% infection, the vine loss had
to be due to Pierces disease spread by GWSS after August
1999, and vines were removed by May 1, 2002. Vineyard replacement
costs per acre were determined by each county. Vines over 10 years
old when removed got a 3% deduction for each year beyond 10 years.
Getting infected wood out early
Early on in the fight, Professor Alexander Purcell (Division of
Insect Biology, Department of Environmental Science at University
of California, Berkeley) told Temecula growers that the best way
to control PD was to remove infected vines. Leaving vines standing
allows disease-free insects to become infected and thus spread
the disease to other vines.
Temeculas willingness to pull out diseased vines early may
prove to be its salvation. Weaver pulled out about 270 (40%) of
Callaways 670 acres in the Temecula area. Peter Poole at
Mt. Palomar removed 30 of his 90 acres of vines.
Between 1999 and 2000, wine grape acreage in Riverside County
decreased 17%. For white wine, the acreage decreased 22%.
Hitting trouble spots early
Temecula growers were also willing to hit the vines and adjacent
citrus with insecticides. They felt they were in a war in which
halfway measures would not work.
Early research suggested that a native parasitic wasp could make
great strides against the GWSS by parasitizing the eggs, but the
wasps will only be part of an integrated pest management solution
for several reasons. At least four species of parasitic wasps,
Gonatocerus ashmeadi, G. triguttatus, Gonatocerus fasciatus, and
G. morelli have been studied in relation to knocking down GWSS.
Mark Hoddle, UC Riverside entomologist, reports that interest
in morelli has waned, while interest in triguttatus has increased.
At least two generations of sharpshooters are produced each year,
a spring and a summer generation. Most of the wasps are effective
on the second generation, but success depends on their effectiveness
on the spring generation.
Several of the wasps were 98% to 100% effective on the summer
generation, but somewhat less so on the spring generation. The
triguttatus seems to be more effective on the spring generation
and therefore holds more interest. Any IPM program including wasps
accepts that some GWSS will remain, and a key is timing of chemical
spraying to effectively manage them and keep insecticide use to
A consensus decision was reached that the wasps alone were not
the way to knock down the sharpshooters coming out of citrus groves.
Winegrowers and citrus growers worked in concert with UC Riverside
and the CDFA to develop a pilot program.
In 2000, part of a CDFA pilot program spent $360,000 to monitor
and treat 1,600 acres of citrus in Temecula Valley. About 234
acres adjacent to vineyards were sprayed by helicopter with Lorsban,
the trade name for a chemical called chlorpyrifos, a broad-spectrum
In 2001, $299,000 was spent for trapping and to apply Admire to
citrus through irrigation. Helicopter spraying was done between
7:30 and 11am on Saturdays when there was less than a five mph
Admire insecticide was applied on citrus through the irrigation
system. It is designed to kill young sharpshooters in the spring.
In the vineyards, Provado, another insecticide, was used.
Prior to this massive effort, Temecula prided itself on a low
input, sustainable approach to agriculture. Pesticide applications
in 2000 have so reduced the GWSS population in Temecula that scientists
now have to go to the Arvin/Bakersfield area to find sufficient
bug populations to study.
Drake, Weaver, and other Temecula growers have also helped mobilize
a state into action. Because of the concerted calls-to-action
of many in the Temecula area and the resulting response from the
CDFA, University of California, the California Legislature, USDA,
and the rest of the state, enormous brain power and research resources
have been brought to bear on the Pierces disease problem.
Everything from antibiotics to pesticides, from native parasitic
wasps to sprays and oils are being tested. Because of the willingness
to get rid of unhealthy vines, infection spread has been slowed.
Because of a concerted spraying effort in 2000, the infestation
of sharpshooters is significantly reduced. But it seems clear
that, at least, Temecula Valley has a fighting chance.
Drake has two vineyard trials to explore grapegrowing with PD.
In March 2002, a new three-acre trial block of Syrah was planted
with 110R rootstock. There was one irrigation at end of April
with Admire added. Several vine rows received 16-oz. per
acre plus a second application to deliver annual maximum of 32-oz.
per year. Several vine rows received a total of 20-oz. of Admire
per acre. Drakes goal is to have 4ppm residual of Admire
in the xylem tissue that would kill sharpshooters if attacked.
Drakes second trial is one acre of five-year-old Cabernet
Sauvignon on 110-R rootstock. There is a comparison/analysis of
adding Admire or Platinum to irrigation water and an evaluation
of application by drip from standard hose or with spaghetti extensions
to deliver irrigation under mulch on the ground to insure delivery
of material to the root zone in the soil.
Weaver has a seven-acre trial for badly damaged sections of the
home vineyard adjacent to the Callaway parking lot. Callaway has
planted to test five different treatments, with one control, in
three irrigation blocks. Two rootstocks, 101-14 and 5BB, will
be used with Clone 7 Cabernet Sauvignon spaced 8X8.
The five treatments include one trial with a balanced fertility
program to see if PD can be successfully combated with fertilizers
One aspect of these trials that excites Weaver is that they involve
a commercial vineyard, not a laboratory, greenhouse, or field
station. Trials done in more controlled settings may get promising
results, but those same results do not obtain outside a controlled
environment, in the complicated and hectic reality of a commercial
Temecula boasts a current population of nearly 70,000 up from only 2,700
just 30 years ago. The area owes its boom and, arguably even its wine
industry to the developers of the planned community of Rancho California.
In 1964, these developers, a partnership composed of Kaiser Aluminum and
Chemical Corporation, Kaiser Industries, Inc., and Macco Realty Company
of Corona del Mar bought the Vail Ranch for $21 million.
The Vail family had run a large cattle ranch carved out of the original
Rancho Temecula Mexican Land Grant since 1904. The new partnership started
a development that would become Rancho California.
A year before they sold to the developers, the Vail Ranch hired Richard
Break, a former UC county agriculture advisor turned agricultural consultant,
to do crop feasibility studies to determine how much of the property could
be planted to citrus. Break discovered that that the ocean breeze that
flows through the Rainbow Gap in the Santa Rosa Mountains makes for cooler
temperatures than surrounding area and could sustain commercial viticulture.
Break was not the first to consider the area for growing wine grapes.
He was following in the footsteps of Jean Louis Vignes, the man who was
arguably Californias first commercial winemaker. Vignes had seen
the areas grapegrowing potential, and tried and failed to claim
land there in 1856.
In 1965, the developers planted a demonstration vineyard with 57 grape
varieties. Richard Break formed a partnership with investors from Fresno
called Temecula Ranchos, to carve out little gentleman farmer
ranchettes with some grapes or citrus.
Brookside Winery started to put things on a commercial footing when it
planted 350 acres of vineyard to supplant its lackluster holdings in neighboring
Cucumonga in 1967. In 1968, Vincenzo Cilurzo, a television studio lighting
designer, planted a vineyard on his 100-acre retirement estate.
Ely Callaway, president of Burlington Industries, bought 150 acres, planted
grapes and started Callaway Vineyards in 1968. Callaway brought determination
and an entrepreneurial flair to the areas grape and wine industry.
Other vineyards and wineries followed. The fledgling Cilurzo and Callaway
wineries were joined by Mt. Palomar, Maurice Carrie, and others.
The bedroom community boomed and the wine industry grew steadily. Callaway
sold his winery to Hiram Walker in 1981, and went on to become the maker
of Big Bertha, the worlds best selling golf club. Temecula became
an American Viticultural Area in 1984, following a heated discussion over
the areas boundaries. Proponents of a larger American Viticultural
Area won out.
The grapes, citrus, and housing all grew as the area boomed. Agricultural
interests and the housing developers were sometimes at odds over whether
subdivisions or Chardonnay would dominate the landscape. Agriculture won
a round in 1989 when Riverside County set aside 5,000 acres on Buck Mesa
as a Citrus and Vineyard Rural Policy Area until 2010. The Temecula area
had struggled with its booming subdivisions and its attractive and growing
wine industry, now coming to a workable if not totally placid agreement.
Fourteen wineries and 2,500 acres of grapes were there in 1996 when vineyard
personnel started to notice a lot of unusual insects. The insects turned
out to be glassy-winged sharpshooters that brought Pierces disease.
Less than 2,000 acres remain today. While the viability of the winegrowing
community in Temecula remains in question, the alternative crop should
grapes prove economically unfeasible is clear: houses.