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John Kabashima
http://calag.ucanr.edu • PUBLISHED ONLINE SEPTEMBER 8, 2016 1
The palm weevil Rhynchophorus vulneratus is
eradicated from Laguna Beach
by Mark S. Hoddle, Christina D. Hoddle, Mohammed Alzubaidy, John Kabashima, J. Nicholas Nisson, Jocelyn Millar and Monica Dimson
In October 2010, Rhynchophorus vulneratus, originally identied as the red palm
weevil, R. ferrugineus, was discovered infesting Canary Island date palms in Laguna
Beach, California. The red palm weevil has caused extensive mortality of palms in the
Mediterranean, the Middle East and North Africa, and its discovery in California caused
concern for the state’s ornamental palm and date industries and the many palms in
Southern California landscapes. A rapid, coordinated eort led to the deployment
of traps baited with the weevil’s aggregation pheromone, coordinated pesticide
applications to privately owned palms and destruction of palms at advanced stages
of infestation. Research conrmed the chemical components of the aggregation
pheromone, assessed the ecacy of trapping strategies and resolved the taxonomic
identity, native range and putative region of origin for the population detected in
Laguna Beach. The last conrmed detection of a live R. vulneratus was Jan. 20, 2012.
USDA-APHIS declared this weevil eradicated from California on Jan. 20, 2015.
The estimated cost of the eradication was $1,003,646.
On Aug. 3, 2010, a badly damaged
Canary Island date palm, Phoenix
canariensis Chabaud (Areca les:
Arecaceae), was removed by a profes-
sional arborist in Laguna Beach, Orange
County, California. Examination of the
crown by the arborist resulted in the re-
covery of adult and larval weevils (Cole-
optera: Curculionidae). This material was
submitted to the Orange County agricul-
tural commissioner’s ofce for identica-
tion on Sept. 1, 2010, and the California
Department of Food and Agriculture
(CDFA) subsequently identied the adult
specimens as Rhynchophorus ferrugineus
(Olivier) (Coleoptera: Curculionidae), the
red palm weevil.
The CDFA’s tentative identication
was conrmed by the United States
Department of Agriculture (USDA) on
Sept. 24, 2010. On Oct. 26, 2010, a live adult
male weevil was recovered from a second
heavily damaged Canary Island date
palm in Laguna Beach. The weevil was
identied as R. ferrugineus by specialists
at the CDFA and USDA (Hoddle 2010a).
These two nd sites were 0.07 miles (0.12
kilometers) apart.
Laguna Beach is a small (~ 8.8 square
miles [23 square kilometers], 23,250 in-
habitants), relatively isolated, wealthy res-
idential area between the Pacic Ocean, to
the west, and the dry, relatively undevel-
oped San Joaquin Hills, to the east. One
north-south highway, California State
Route 1, and one west-east highway, State
Route 133, run through Laguna Beach; the
city has no airport, seaport or interstate
Online: http://dx.doi.org/10.3733/ca.2016a0012
Published online September 8, 2016
Adult male Rhynchophorus vulneratus
recovered from an infested Canary
Island date palm in Laguna Beach.
Research Article
border crossings. Tourism is a major in-
dustry, with ~ 3 million people visiting
the city annually (Turnbull 2004).
Rhynchophorus spp. weevils, especially
R. ferrugineus, are notoriously destructive
palm pests in native and invaded ranges
(Faleiro 2006; Murphy and Briscoe 1999).
R. ferrugineus attacks more than 40 palm
species in 23 genera. It is a destructive
pest of the coconut palm, Cocos nucifera
L. (Arecales: Arecaceae), (Giblin-Davis et
al. 2013) in its native range, which is the
northern and western regions of continen-
tal Southeast Asia (e.g., northern Thailand,
Vietnam and Cambodia), Sri Lanka and
the Philippines (Rugman-Jones et al. 2013).
Accidental introduction of R. ferrugineus
into regions outside of its native range
has occurred via the movement of live
palms infested with weevils, and this
pest has caused extensive mortality of P.
canariensis in the Mediterranean and of
date palms (Phoenix dactylifera L.) in the
Middle East and North Africa (Faleiro
2006; Faleiro et al. 2012; Giblin-Davis et al.
2013; Murphy and Briscoe 1999).
Discovery of red palm weevil in
California was of major concern because
the ornamental palm and date industries
are estimated, respectively, at $70 million
and $34 million annually (CDFA 2013),
and palms are ubiquitous in Southern
California landscapes. Furthermore, the
native California fan palm, Washingtonia
lifera (Lindl.) H.Wendl. (Arecales:
Arecaceae), restricted to a limited range
comprising desert riparian habitats in the
western United States, was considered
vulnerable because it is a known host for
R. ferrugineus (Ju et al. 2011; Longo et al.
2011).
Weevil biology
Palm mortality caused by R. ferrugin-
eus results from internal feeding by larvae
(mature larvae can exceed ~ 2 inches [5
centimeters] in length), which are con-
cealed within the palm during the entire
larval life cycle, making detection of early
infestations and subsequent control dif-
cult (Giblin-Davis et al. 2013). Internal
feeding by two or three generations of
weevil larvae over 1 to 2 years can kill
infested palms. Palm death results from
mortality of apical growing areas (typical
for C. nucifera and P. canariensis) or trunk
collapse (typical for P. dactyli f e ra) (Faliero
2006; Giblin-Davis et al. 2013; Murphy and
Briscoe 1999).
A second Southeast Asian palm
weevil species, R. vulneratus (Pa n zer),
was reported to have a more southern
distribution in Asia than R. ferrugineus
(Wattanapongsiri 1966). A taxonomic
revision by Hallett et al. (2004), with
specimens collected from west Java, in
Indonesia, separated the species pri-
marily on the basis of color differences,
with R. vulneratus typically being black
with a red stripe on the dorsal surface
of the thorax and R. ferrugineus being
orange with black markings). Unable
to nd any signicant molecular, mor-
phological or behavioral differences or
mating incompatibilities between these
two color morphs, Hallett et al. (2004)
synonymized R. vulneratus with R. fer-
rugineus, with R. ferrugineus having nam-
ing priority. Therefore, the black palm
weevils with a prominent red stripe
on the dorsal surface of the thorax (i.e.,
the R. vulneratus morph) discovered in
Laguna Beach were ofcially identied
as R. ferrugineus.
Subsequent work investigating the
origin of the palm weevil invasion in
Laguna Beach used molecular markers
to investigate the identity of the species
detected and to ascertain its probable area
of origin. DNA-based analyses of weevils
collected throughout the presumptive
native ranges of R. ferrugineus and R. vul-
neratus concluded that the weevil species
collected in Laguna Beach was R. vulnera-
tus, a species distinct from R. ferrugineus.
Molecular analyses by Rugman-Jones
et al. (2013) indicated that R. vulneratus
has a native range conned largely to
southern Thailand and northern Malaysia
on the Malay Peninsula, Singapore, and
Indonesia, and that this species has a
range of color forms, including that typi-
cal of the invasive R. ferrugineus (g. 1).
The results of these molecular studies
on species identities and geographic
distributions supported earlier work by
Wattanapongsiri (1966). It was concluded
that Hallett et al. (2004) had been study-
ing different color morphs of R. vulneratus
in Java and that R. vulneratus had been
incorrectly synonymized with R. ferru-
gineus (Rugman-Jones et al. 2013). From
this point forward, we will refer to the
weevil species found at Laguna Beach as
R. vulneratus.
The only nd of R. vulneratus outside
of its native range has been in Laguna
Beach. The nearest molecular match to
the Laguna Beach population was with
R. vulneratus collected in Bali, Indonesia
(Rugman-Jones et al. 2013). It was hypoth-
esized that the introduction of R. vulnera-
tus into Laguna Beach may have been
Fig. 1. Two color morphs of Rhynchophorus vulneratus recovered from an infested coconut palm in Java, Indonesia. (A) The orange and black morph of
R. vulneratus (left) is very similar in appearance to R. ferrugineus. The black morph with the red dorsal stripe (right) is similar to adult R. vulneratus
recovered in Laguna Beach. (B) Two color morphs of R. vulneratus copulating.
(A) (B)
Mark Hoddle
Mark Hoddle
2 CALIFORNIA AGRICULTURE • DOI: 10.3733/ca.2016a0012
deliberate, possibly to start a local source
of palm weevil larvae and pupae to be
used in the preparation of traditional
Asian dishes (Hoddle 2015).
Response in Laguna Beach
To delineate the areas in Laguna
Beach infested by R. vulneratus, 1-gallon
(3.78-liter) bucket traps were loaded with
Ferrolure 700 mg (ChemTica Internacional
S.A., Costa Rica), which contains the ag-
gregation pheromone 4-methyl-5-nonanol
(ferrugineol). Also in the bucket were
ethyl acetate (a synergist), fermenting
apples as bait and 0.26 gallon (1 liter) of a
50:50 mixture of water and propylene gly-
col (to drown and preserve weevils).
Trapping commenced Oct. 7, 2010. A
total of 150 traps were deployed by CDFA
at two different densities within a survey
area of 6 square miles (15.6 square kilo-
meters; ~ 68% of the land area of Laguna
Beach). High-density trapping was set
at 50 traps per 1 square mile (2.6 square
kilometers) around nd sites. Outside of
this zone, 25 traps were deployed per 1
square mile (2.6 square kilometers). Two
additional traps (total number used for
monitoring was 152) were deployed at a
green waste facility 15 miles (24 kilome-
ters) south of the nd sites to monitor for
weevils inadvertently moved there in dis-
posed palm material. Traps were attached
to palm trunks ~ 6.6 feet (2 meters) above
the ground and inspected daily from
Oct. 7, 2010, to Oct. 17, 2010, weekly until
March 19, 2011, then biweekly until Jan. 20,
2015, when eradication was declared.
Visual surveys of 13,485 palm trees
for weevil damage on 1,963 properties
within 6 square kilometers of the initial
nd sites were conducted by CDFA over
the period Sept. 27, 2010, to Oct. 28, 2010.
Detection of empty pupal cases or body
fragments of dead adult weevils con-
rmed the presence of this pest in ve
survey locations. Visual surveys were
aided by a large response from residents,
local arborists and palm enthusiasts.
Reports of symptomatic palms by these
groups were investigated by CDFA and
Orange County program personnel, and
cooperating home owners provided ac-
cess to private properties. Survey results
in Laguna Beach indicated that the area
infested with R. vulneratus was ~ 0.39
square miles (1 square kilometer), which
equated to ~ 4% of the land area of the
city of Laguna Beach.
The public response to outreach ef-
forts and subsequent surveys resulted
in another pest discovery in Southern
California: the rst conrmation of the
South American palm weevil, R. pal-
marum (L.) (g. 2), in California and the
neighboring state of Baja California,
Mexico (Hoddle 2011a). The high mortal-
ity of Canary date palms in Tijuana since
at least 2011 has been the source of wee-
vils entering Southern California, and it
is likely that R. palmarum will become a
problematic pest of ornamental, date and
native palms in California, as there are
increasing reports of P. canariensis being
killed by this pest in San Ysidro in San
Diego County. At this time there are no
active programs targeting R. palmarum in
Southern California.
A technical working group (TWG) was
assembled by the USDA to provide expert
input into the emerging monitoring and
management program for R. vulneratus
in Laguna Beach. The TWG included in-
ternational palm weevil experts, research
scientists from UC Riverside, CDFA
and USDA, UC Cooperative Extension
personnel from San Diego, Orange and
Los Angeles counties and county ento-
mologists from the agricultural commis-
sioner’s ofces in Orange and San Diego
counties.
The TWG met at Laguna Beach from
Nov. 29 to Dec. 1, 2010 (Hoddle 2010b).
The group produced a document with
recommendations pertaining to (1) detec-
tion and identication of visual symp-
toms typifying infestations, (2) trapping
guidelines, (3) assessment of techniques
for early detection of infestations, (4) pes-
ticide treatments, (5) removal and destruc-
tion of infested palms and (6) education,
outreach and information dissemination
to local communities and palm industry
professionals (Hoddle 2010c; Hoddle
2011b; Hoddle 2011c).
Despite evidence of damaged palms
in Laguna Beach, baited pheromone traps
captured only one adult weevil, which
was found on Jan. 18, 2012, within 0.21
kilometer of the original nd sites. In re-
sponse to this nd, between Jan. 31, 2012,
and Feb. 15, 2012, visual surveys of palms
for weevil infestations were conducted by
CDFA within an area of 0.6 square miles
(1.6 square kilometers). A total of 5,564
palm trees were inspected on 782 prop-
erties. Two additional properties with
palms exhibiting characteristic weevil
feeding damage to fronds (leaf notching
or holes in the petiole base) were identi-
ed. However, weevil presence (pupal
cases or adult weevils) was not conrmed.
Fig. 2. Rhynchophorus palmarum adult (A) and larva (B) extracted from a cocoon of palm bers. Both were collected from an infested Phoenix canariensis
in Tijuana, Mexico. This weevil was detected as a result of the public’s response to requests for help with the R. vulneratus invasion in Laguna Beach.
R. palmarum may have established in San Diego County and potentially poses a serious threat to California’s palms.
(A) (B)
Mark Hoddle
Mark Hoddle
http://calag.ucanr.edu • PUBLISHED ONLINE SEPTEMBER 8, 2016 3
The low capture rates of R. vulneratus
in pheromone traps in areas with ap-
parent or suspected weevil infestations
caused concern because it suggested
that the pheromone traps might not be
attractive to R. vulneratus. If this was
the case, then the lack of a sensitive and
species-specic monitoring tool
could signicantly impair the
management program targeting
R. vulneratus.
Verifying pheromone
compounds
Hallet et al. (1993) identied
two aggregation pheromone com-
ponents, 4-methyl-5-nonanone
(ferrugineone) and 4-methyl-
5-nonanol (ferrugineol), produced
by male R. vulneratus (they incorrectly
assumed that they were working with R.
ferrugineus) collected in Java, Indonesia.
To verify the chemical identify of the ag-
gregation pheromone of R. vulneratus as
reported by Hallett et al. (1993), male and
female weevils were eld collected by
authors Mark and Christina Hoddle in
Sumatra, Indonesia, and used for phero-
mone collection.
Pheromone collections and controls
consisted of four treatments: (1) a steril-
ized mesh container only, (2) four male
weevils on a food source (either sugar-
cane or oil palm hearts, used separately in
case one stimulated pheromone produc-
tion), (3) four female weevils on a food
source and (4) the food source used in
2 and 3 without weevils. All treatments
were placed inside heat-sterilized mesh
containers, which in turn were enclosed
by odorless Terinex oven bags (Terinex
Ltd., Bedford, U.K.). The mesh containers
held the weevils and food and prevented
weevils from chewing holes in the oven
bags and escaping.
Treatments 1 and 4 provided control
chemical proles of volatiles from the
mesh cage and the food sources, and
treatments 2 and 3 provided proles of
volatiles released by male and female
weevils. An aquarium pump was used to
push puried air into the oven bags over
the mesh containers, food and weevils,
and as the airstream exited, it was passed
through activated charcoal lters, which
trapped the volatiles released into the air-
space of the bags by the weevils or food
items (g. 3A).
Fig. 3. (A) Rhynchophorus vulneratus pheromone aeration set up in an outdoor screen house in Sumatra,
Indonesia. (1) Terinex odorless oven bag enclosing a sterilized wire mesh container holding adult male
or female weevils with food (see inset photo). (2) Inlet with 6 to 14 mesh activated charcoal lter to
purify ingoing air. (3) Outlet with thermally desorbed 50 to 200 mesh activated charcoal collector to
collect volatile compounds emitted by weevils and food items. (4) Manifold to regulate airow. (5)
Aquarium pump to push and pull air through oven bags. (6) Airow meters. (B) GC–MS chromatograms
of volatiles collected from male and female R. vulneratus and the oil palm (food source for weevils)
control. Peaks 1 and 2 in the chromatogram for male weevils are 4-methyl-5-nonanone (ferrugineone)
and 4-methyl-5-nonanol (ferrugineol), respectively. Schematic prepared by Steve McElfresh.
Males
Abundance (X10
5
)
Time (min)
0
10
20
30
0
10
20
30
0
10
20
30
4 6 8 10 12 14 16 18
Oil palm control
(B)
1
2
Females
Christina Hoddle
1
2
3
45
6
(A)
4 CALIFORNIA AGRICULTURE • DOI: 10.3733/ca.2016a0012
Aerations were made continuously
for 3 to 4 days, and treatments were rep-
licated four times. The trapped volatiles
were eluted from the charcoal collectors
and analyzed by coupled gas chromatog-
raphy–mass spectrometry (GC–MS). The
insect-produced compounds were tenta-
tively identied by interpretation of their
mass spectra, and these identications
were veried by comparing the GC reten-
tion times and mass spectra with those
of authentic standards obtained from
ChemTica.
The analyses showed that two male-
specic compounds were produced by
R. vulneratus in Sumatra, and they were
conclusively identied as the two previ-
ously reported aggregation pheromone
components obtained for R. vulneratus
from Java (Hallett et al. 1993) (g. 3B).
This result raised an important question:
What are the aggregation pheromones for
R. ferrugineus? The commercially available
aggregation pheromone used for R. ferru-
gineus management was identied from R.
vulneratus (Hallett et al. 1993), and to our
knowledge, the identity of the aggrega-
tion pheromone produced by R. ferrugin-
eus has not yet been determined, although
this species is attracted to baited traps
containing ferrugineol and ferrugineone
derived from R. vulneratus.
Field evaluations of
baited traps
The attractiveness of traps loaded
with fermenting bait, ethyl acetate and
Ferrolure 700 mg was eld-tested in
the Philippines (R. ferrugineus was the
species present at study sites on Luzon
Island) and Indonesia (R. vulneratus was
the species present on Sumatra). At the
time these eld studies were conducted, it
was assumed that R. ferrugineus was the
subject of this work and the only species
present in both countries.
In the Philippines, three different
treatments were tested for attractiveness
to weevils; traps were baited with (1) fer-
menting dates or pieces of coconut palm
heart, ethyl acetate and aggregation pher-
omone, (2) freshly cut coconut palm logs
only and (3) a combination of treatments
1 and 2 (Hoddle and Hoddle 2011). This
experiment was repeated in Sumatra and
results were similar: baited pheromone
traps combined with freshly cut palm
logs, treatment 3, were very attractive to
R. vulneratus (Hoddle and Hoddle 2015).
The volatiles from cut palm logs likely
act synergistically with the aggregation
pheromones to increase attraction (Hallett
et al. 1993).
A combination of traps and cut date
palm trunks (date palms were used be-
cause coconut palms were not available)
was tested in Laguna Beach to determine
if it would result in captures of R. vulnera-
tus in areas where activity was observed
but no weevils had been caught in traps.
Date palm sections were obtained from a
commercial palm producer in Coachella
Valley, California. Three sites around ar-
eas with suspected R. vulneratus act ivity
in Laguna Beach were selected for weevil
monitoring with sections of date palm
trunks and pheromone traps.
Sections of cut apical parts of palm
trunks were stacked beside P. canariensis
palms and baited pheromone traps were
deployed on top of these stacks. Traps
were checked daily from June 21, 2012, to
July 17, 2012, for a total of 27 consecutive
days. No weevils were found in traps or
log stacks. This trial was repeated Oct. 18,
2012, to Nov. 11, 2012, a 27-day period. No
weevils were recovered from the second
trial (see Hoddle 2012 for more details).
Palm removals, and pesticides
On Nov. 3, 2010, the infested Canary
Island date palm that yielded a live male
weevil on Oct. 26, 2010, was removed
from Laguna Beach and disposed of in
compliance with strict destruction proto-
cols (Hoddle 2010d). No live larvae, pupae
or adult weevils were found inside the
trunk or petioles. This palm was the only
one removed as part of the R. vulneratus
management program.
A total of 13 palm trees were treated
with broad-spectrum contact pesticides
applied to foliage and/or systemic pesti-
cides that were applied via trunk or soil
injections (Hoddle 2011d; Hoddle 2011e):
three P. canariensis (two with conrmed
infestations; treated once each), ve
Howea forsteriana Becc. (suspected infes-
tations based on visual damage assess-
ments; treated three times from August to
December 2011), one Chamaerops sp. (sus-
pected; treated once) and four Roystonea
sp. (suspected; treated twice from March
to April 2012).
One P. canariensis with conrmed
R. vulneratus activity was treated with
pesticides Jun. 2, 2011 (Hoddle 2011e),
then cut down and removed from a pri-
vate residence in Laguna Beach on Mar.
27, 2013, because it was causing structural
damage to an adjacent building (Hoddle
2013). The palm crown and petiole bases
on individual fronds were examined for
R. vulneratus feeding damage. There was
no visual evidence of feeding damage,
and no larvae, pupal cases or adults (dead
or alive) were found (Hoddle 2013).
Declaration of
eradication, cost
On Jan. 20, 2015, USDA-APHIS of-
cially declared eradication of R. fer-
rugineus (i.e., R. vulneratus) from Laguna
Beach, 3 years after the last detection of
a single live weevil on Jan. 18, 2012 (El-
Lissy 2015). The eradication declaration
was made in accordance with European
and Mediterranean Plant Protection
Organization International Standards,
which require a period of 3 consecutive
years with no pest detections (El-Lissy
2015).
Despite signicant data supporting
R. vulneratus as the invasive weevil spe-
cies in Laguna Beach (Rugman-Jones
et al. 2013), USDA-APHIS states that it
will “continue to refer to this detection as
Rhynchophorus ferrugineus until additional
information is available” (Molet et al. 2011,
revised 2014). This stance is based on the
desire of USDA-APHIS for a combined
dataset of morphological and DNA in-
formation, as well as discrete species di-
agnoses, to resolve remaining taxonomic
uncertainty (Eileen Smith, USDA-APHIS,
personal communication, Mar. 31, 2015).
Canary Island date palm killed by Rhynchophorus
vulneratus in Laguna Beach (note healthy Canary
Island date palms in the background).
John Kabashima
http://calag.ucanr.edu • PUBLISHED ONLINE SEPTEMBER 8, 2016 5
The cost of the eradication of R. vulneratus from Laguna
Beach was estimated at $1,003,646. A breakdown of estimated
expenditures is provided in table 1.
Success factors
Eradication of an invasive arthropod pest depends on mul-
tiple interacting factors. Specically, small infested areas that
can be monitored with highly specic and sensitive tools (e.g.,
pheromone-baited traps) have higher eradication success prob-
abilities. Furthermore, the smaller the area being treated, the
less it costs to eradicate the target (Tobin et al. 2014). These fac-
tors likely contributed, in part, to the successful eradication of R.
vulneratus from Laguna Beach.
Social, economic, regulatory and political factors also are
critical components of eradication programs (Pluess et al. 2012).
These may include the authority of regulatory agencies to inter-
vene and take action on private and public lands, procurement
of funds to support the project, the commitment and political
will of stakeholders affected by the invasion and, very impor-
tantly, strong public support for eradication efforts (Tobin et al.
2014). The R. vulneratus eradication effort beneted from strong
socioeconomic support.
Organisms need to maintain populations above a critical
density, the Allee threshold, if they are to persist. Below this
threshold, populations trend toward extinction (Liebhold and
Tobin 2008; Suckling et al. 2012). Factors negatively inuencing
the Allee threshold and increasing extinction risk may include
(1) unsuitable climate, (2) suboptimal foods, (3) low genetic
TABLE 1. Estimated costs for the program that eradicated
Rhynchophorus vulneratus from Laguna Beach,
September 2010 to January 2015
Expenditure item
Estimated
cost ($)
Labor for visual inspections of palms and monitoring of baited
pheromone traps in Laguna Beach
230,000
Bucket traps and supplies for maintaining traps (pheromones,
fruit, etc.) in Laguna Beach
32,000
Travel to monitor traps (vehicle rental and gas) in Laguna Beach 60,000
Salary estimates for CDFA, UC and county agricultural
commissioner employees involved in palm weevil monitoring,
management and research
230,000
CDFA Specialty Crop Block Grant that supported molecular
analyses of weevils, testing of pheromones and trapping
strategies in native and invaded ranges, and identication of
aggregation pheromones collected from R. vulneratus in Sumatra,
Indonesia
108,446
Pesticide applications to 13 palm trees in Laguna Beach 1,200
Four date palms used for enhanced trapping trials at Laguna
Beach ($3,000 per palm)
12,000
Outreach and extension materials and community meetings for
stakeholders
30,000
Miscellaneous costs, including rental of bucket trucks (cherry
pickers) to inspect palms; palm removal, transport and disposal;
cameras, binoculars; etc.
20,000
Statewide monitoring program for invasive palm weevils in other
areas of California, outside of Laguna Beach (998 traps deployed
in 12 counties)
280,000
TOTA L 1,003,646
Fig. 4. Average monthly comparisons between Laguna Beach, California, and
Denpasar, Bali, Indonesia for (A) temperature, (B) rainfall and (C) humidity.
Sources: www.usa.com/laguna-beach-ca-weather.htm and www.weatherbase.com/
weather/weather.php3?s=592525&cityname=Denpasar-Bali-Indonesia&units=metric.
Denpasar, Bali
Laguna Beach
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Average relative humidity (%)
Month
0
20
40
60
80
100
Denpasar, Bali
Laguna Beach
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Average rainfall (mm)
Month
0
50
100
150
200
250
300
350
400
Denpasar, Bali
Laguna Beach
Average temperature (˚C)
0
5
10
15
20
25
30
35
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Month
(A)
(C)
(B)
6 CALIFORNIA AGRICULTURE • DOI: 10.3733/ca.2016a0012
variability and (4) control tactics such as
the use of pesticides. The interaction of
some or all of these factors may have con-
tributed to the successful eradication of R.
vulneratus.
First, the climate in Laguna Beach may
not have been suitable for vigorous year-
round population growth of the weevil.
Average monthly temperatures and rain-
fall are lower in Laguna Beach than in
Bali, Indonesia (g. 4), where weevils with
the closest genetic match to specimens
collected from Laguna Beach were found
(Rugman-Jones et al. 2013). Second, low
genetic variability due to the small size of
the founding population (Rugman-Jones
et al. 2013) may have reduced the tness
of the founding population. Third, the
suitability of Phoenix spp. and other palm
species as hosts for R. vulneratus is not
known, and P. canariensis may be of mar-
ginal quality as a host. Collectively, when
coupled with targeted pesticide applica-
tions to infested palms, these factors may
have suppressed population growth and
pushed weevil densities below the Allee
threshold, resulting in the extinction of
this palm pest at Laguna Beach. c
M.S. Hoddle is UC Cooperative Ex tension (UCCE)
Specialist in Biological Control in the Department of
Entomology and Director of the Center for Invasive
Species Research at UC Riverside; C.D. Hoddle is Assistant
Specialist in the Department of Entomology at UC
Riverside; M. Alzubaidy is Senior Environmental Scientist
at CDFA, Pest Detection/Emergency Projects, Anaheim;
J. Kabashima is UCCE Environmental Horticulture
Advisor Emeritus at South Coast Research and Extension
Center, Irvine; J.N. Nisson is Entomologist at Orange
County Agricultural Commissioner’s Oce, Tustin; J.
Millar is Professor of Entomology in the Department
of Entomology at UC Riverside; and M. Dimson is Sta
Research Associate at South Coast Research and
Extension Center, Irvine.
We are grateful to Duane Young, Cocopah
Nurseries, for donating date palms. Albert Keck an d
Hadley Dates provided logistical suppor t. We appreciate
the cooperation of homeowners in Laguna Beach
who provided unrestricted access to their properties
and cooperated with surveys, enhanced trapping
trials and pesticide treatments of infested palms. We
thank Kevin Homan, Laura Petro and Debby Tanouye
(CDFA) and Helene Wright (USDA) for assistance. We
acknowledge the suppor t of Marcie Johnson, Gilbert
Vargas (arborist), West Coast Arborists, City of Laguna
Beach, Target Specialty Products, Ed Black and RPW
Services for assistance with surveys for infested palms
and treating infestations. We are indebted to Stephen
Nelson, Ahmed Saleh, Lisanti Cahyasiwi, Adi Sumantri,
Linda Purwaninigsih and Prima Wijayanto, and
also to Sumatra Bioscience and Bah Lias Research
Station (Lonsum) for their outstanding hospitality and
generous assistance with pheromone eld evaluations
and aeration trials in Sumatra, Indonesia. We thank
Carmela Balcazar, of Villa Escudero Plantations, San
Pablo, Philippines, for facilitating pheromone eld trials
in a commercial coconut plantation in the Philippines.
Research in support of this project was suppor ted,
in part, by a CDFA Specialty Crops Grant, SCB11061,
“Addressing Urgent Research Needs for Red Palm Weevil
in California.”
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http://calag.ucanr.edu • PUBLISHED ONLINE SEPTEMBER 8, 2016 7
