California Agriculture

Volume 59, Number 4 2005 Page 223

Introduced parasitic wasps could control glassy-winged sharpshooter

Leigh J. Pilkington Nicola A. Irvin Elizabeth A. Boyd Mark S. Hoddle Serguei V. Triapitsyn Bryan G. Carey Walker A. Jones David J.W. Morgan

Copyright c 2005 by Regents of the University of California, unless otherwise noted. This article is part of the collected publications of California Agriculture. California Agriculture is archived by the eScholarship Repository of the California Digital Library. Abstract

The glassy-winged sharpshooter (GWSS) is an introduced pest that spreads the bacterium Xylella fastidiosa, which causes a variety of diseases such as Pierce’s disease in grapevines and leaf scorch in oleanders. GWSS has been established in Southern California since about 1990 and has also successfully invaded French Polynesia, Hawaii and Easter Island. Researchers from UC, the U.S. Department of Agriculture and the California Department of Food and Agriculture have introduced parasitic wasps for the biological control of GWSS. Four parasitoids from the southeastern United States have been released and appear to be establishing in Southern California. Parasitoids from Argentina are also being evaluated in quarantine but have not yet been released.

Keywords: glassy-winged sharpshooter, Xylella fastidiosa, biological control, Pierce’s disease, oleander leaf scorch, Mymaridae, parasitoids, Homalodisca coagulata, Gonatocerus

Suggested Citation: Leigh J. Pilkington, Nicola A. Irvin, Elizabeth A. Boyd, Mark S. Hoddle, Serguei V. Triapitsyn, Bryan G. Carey, Walker A. Jones, and David J.W. Morgan (2005) “Introduced parasitic wasps could control glassy-winged sharpshooter”, California Agriculture: Vol. 59: No. 4, Page 223. http://repositories.cdlib.org/anrcs/californiaagriculture/v59/n4/p223 REVIEW ARTICLE ▼ Introduced parasitic wasps could control glassy-winged sharpshooter

Leigh J. Pilkington Nicola A. Irvin Elizabeth A. Boyd Mark S. Hoddle Serguei V. Triapitsyn Bryan G. Carey Walker A. Jones David J.W. Morgan ▼

The glassy-winged sharpshooter (GWSS) is an introduced pest that The glassy-winged sharp- spreads the bacterium Xylella fastidi- shooter, above, a native sharpshooter pest in the osa, which causes a variety of diseases southeastern United States such as Pierce’s disease in grapevines and northeastern Mexico, is now well established in and leaf scorch in oleanders. GWSS California, Hawaii, Tahiti and has been established in Southern Easter Island. Left, Pierce’s disease, which is transmitted California since about 1990 and has by bacterium vectored by the also successfully invaded French sharpshooter, is having an economic impact on California Polynesia, Hawaii and Easter Island. grape growers. Researchers from UC, the U.S. Depart- ment of Agriculture and the California Department of Food and Agriculture have introduced parasitic wasps for the biological control of GWSS. Four parasitoids from the southeastern United States have been released and appear to be establishing in Southern California. Parasitoids from Argentina are also being evaluated in quarantine but have not yet been released. Photos: Jack Kelly Clark Kelly Jack Photos:

he glassy-winged sharpshooter of coevolved natural enemies, coupled crease. Already the bacterium has been (GWSS) is a native insect of the with the irrigation of agricultural and found to cause two previously unrec- southeasternT United States that has be- urban areas in desert habitats that ognized diseases in olive trees and come extremely pestiferous in Southern would otherwise be too dry to support liquidambar, where it causes scorchlike California, where it became established GWSS populations (Hoddle 2004a). symptoms. The GWSS-Xylella combina- around 1990 (Sorensen and Gill 1996), The GWSS feeds exclusively on xy- tion has devastated or has the potential possibly imported as eggs on nurs- lem fluids, and its ability to spread the to devastate many agricultural crops, ery or private plant material. GWSS xylem-dwelling plant pathogenic bac- native vegetation, and urban ornamen- (Homalodisca coagulata Say [Homoptera: terium Xylella fastidiosa is at the core of tal and landscape plants. The potential Cicadellidae]) is now widely established its classification as a pest in California. effect of GWSS vectoring X. fastidiosa in several Southern California counties In California, the GWSS-X. fastidiosa into native California vegetation that (CDFA 2003) (fig. 1, page 224), and suc- combination causes Pierce’s disease previously had no association with the cessfully invaded Tahiti in 1999 (Cheou in grapes, almond leaf scorch, alfalfa bacterium may lead to new epidem- 2002), Hawaii in 2004 (Hoover 2004) dwarf disease and oleander leaf scorch. ics, and so is particularly worrisome. and Easter Island in 2005.* The insect’s In addition, the number and type of Consequently, the establishment of population growth in California has plant maladies caused by GWSS- GWSS in California has irrevocably been extraordinary, facilitated by a lack vectored X. fastidiosa is likely to in- changed the ecology of X. fastidiosa in

http://CaliforniaAgriculture.ucop.edu • OCTOBER–DECEMBER 2005 223 *GWSS was first detected on Easter Island in August 2005. There appear to be no natural enemies attacking GWSS and it has been observed feeding on citrus, mangoes, guava and Bougainvillea (Sandra Ide, personal communication, October 2005). GWSS has shown strong invasive potential, having become established in a variety of places outside its native range, including California, French Polynesia, Easter Island and Hawaii.

California’s wilderness, agricultural and in California are being pursued by urban landscapes. researchers at UC Riverside, the The presence of Xylella in Tahiti and U.S. Department of Agriculture’s Hawaii is currently unknown. It is pos- Agricultural Research Service (USDA- sible that the bacterium was introduced ARS) and the California Department to these South Pacific islands via the of Food and Agriculture (CDFA). importation of ornamental plants from Biological control involves identifying areas in the Americas where Xylella is natural enemies of the target pest. After native. These ornamental plants could the control agent is deemed safe and be silent Xylella reservoirs that harbor cleared from secure quarantine facilities, the bacteria without expressing disease they are released into the environment, Fig. 1. GWSS establishment in California symptoms. However, once a vector such where they utilize the pest as food and counties and infested parts of counties. as GWSS arrives, they could transmit thereby regulate its population growth the bacteria to susceptible host plants. and subsequent abundance. In the southeastern United States Economic impact of GWSS and northeastern Mexico, GWSS eggs The economic costs to California are parasitized by several species of attributed to GWSS are immense. For mymarid and trichogrammatid para- tance from human intervention). While example, oleander leaf scorch has sitic wasps. The most common natural G. ashmeadi may have established on caused damage in excess of an esti- enemies associated with GWSS eggs in early GWSS populations, it more likely mated $52 million on 2,000 miles of the southeastern United States are all established on the native smoke-tree freeway median plantings (Costa et al. mymarid wasps: Gonatocerus ashmeadi sharpshooter (Homalodisca liturata Ball) 2000). In 1998 and 1999 grape growers Girault, G. triguttatus Girault, G. mor- (Vickerman et al. 2004). in Riverside and San Diego counties ac- rilli Howard and G. fasciatus Girault While these two species were already crued estimated losses of $37.9 million (Triapitsyn and Phillips 2000). In the established, additional introductions of due to Pierce’s disease (Siebert 2001). In late 1990s, in an effort to use natural the same species may be more effective. 2000, researchers in cooperation with enemies to control GWSS popula- For example, the introduced southeast- affected grape and citrus growers spent tions in Southern California, UC and ern parasitoid populations may exhibit $6.9 million to apply spray applications CDFA imported these four parasitoids a greater ability to tolerate cool winter of Admire and Assail (acetamiprid) from southeastern states, cleared them temperatures and dry conditions, or be directly on GWSS habitat in Temecula through quarantine and introduced more aggressive reproductively. These and Bakersfield, in an effort to manage them into California urban and agricul- characteristics could help the parasit- populations migrating into vineyards. tural areas. oids become established and make them In 2002, primary producers incurred ad- G. triguttatus was first released more effective as control agents. The ditional economic costs resulting from in fall 2000 in Riverside, Ventura new parasitoid stock will likely increase GWSS containment activities such as and Kern counties. G. ashmeadi and the genetic variability of the already inspections of export nursery stock and G. morrilli releases started in 2001, and established G. morrilli and G. ashmeadi shipments of bulk grapes and citrus G. fasciatus in 2002. Anagrus epos (from populations, which could lead to im- from GWSS-infested counties (CDFA Minnesota) releases started in 2005. proved biological control. 2003). There are currently more than Over 1.2 million parasitoids have now CDFA has also made more than 70 state and federal research programs been released in 13 California counties 90 separate recoveries of egg masses studying GWSS or X. fastidiosa. where GWSS populations have been parasitized by G. triguttatus or G. fas- Traditional pesticide use and cultural reported. More than 1,900 releases ciatus at 23 sites in seven Californian practices to assist in reducing the popu- have been made at 373 release sites counties, suggesting that these control lations of GWSS may be augmented by covering agricultural, riparian and agents are becoming established. a long-term and cost-effective use of urban environments (see CDFA [2005] Biological control is a long-term biological control, an area heavily re- for release locations). strategy for the suppression of GWSS searched in California with a history of Two of these species (G. morrilli in areas where it has already become success. and G. ashmeadi) are already estab- established. To this end, CDFA has lished in California. G. morrilli is na- established two facilities based in Biological control strategies tive to California and G. ashmeadi is Riverside and Kern counties to mass Classical biological-control strate- self-introduced from the southeastern produce, release and monitor in- gies to reduce GWSS populations United States (with no direct assis- troduced biological control agents.

224 CALIFORNIA AGRICULTURE • VOLUME 59, NUMBER 4 ▼ Parasitoids can aid in control of the glassy- G. ashmeadi G. triguttatus winged sharpshooter. Clockwise, from upper left: Gonatocerus ashmeadi is widespread in California and was most likely self-intro- duced from the southeastern United States and northeastern Mexico; G. triguttatus is a subtropical and tropical species introduced into California from Mexico and southeast- ern Texas; G. morrilli, native to Southern Cal- ifornia, is having its genetic pool augmented with conspecifics collected from other U.S. regions; G. fasciatus is native to the south- east and Midwest and has gregarious repro- ductive habits.

G. fasciatus G. morrilli

(Proconiini) and genus (Homalodisca) as GWSS, and is similar to the GWSS in its egg-laying and generalist plant-feeding habits. As such, it is expected to be uti- lized by introduced Gonatocerus spp. Scientists at UC Riverside are in- vestigating three other common na- tive sharpshooters (Cicadellinae). Preliminary observations have revealed Photos: Jack Kelly Clark Kelly Jack Photos: that the GWSS parasitoids may affect their populations. However, the habi- USDA-ARS and CDFA have also been cies and the food web on which they all tats occupied by these common native evaluating the safety of mymarid depend. sharpshooters have less overlap with parasitoids imported from Argentina UC and CDFA scientists screened the GWSS, and they are from different for possible use against GWSS in all introduced GWSS biological con- tribes. The habitats of the Cicadelline California. Quarantine work at UC trol agents for their ability to parasit- sharpshooters (X. fulgida) and the green Riverside indicates that Argentinean ize closely related nontarget species sharpshooter (Draeculocephala minerva parasitoids will readily attack GWSS of Homoptera found in the area of Ball) both consist of grasses such as even though they did not evolve in the introduction. These include the south- Bermuda and Johnson grass (Cynodon native range of GWSS. These evalua- eastern species H. insolita (Walker) dactylon [L.] and Sorghum halapense [L.] tions are ongoing and no releases have and the southwestern species H. litu- respectively), making them improbable been made. rata (both Proconiine sharpshooters); hosts for Gonatocerus spp. The blue- three sharpshooters of the Cicadellini green sharpshooter (G. atropunctata), Nontarget impact of parasitoids tribe, Colladonus montanus (Van also of the Cicadellini tribe, prefers Biological control has come under Duzee) (Cherry mountain leafhopper), humid, partially shaded and densely increased scrutiny because there is some Graphocephala atropunctata (Signoret) vegetated habitats. This sharpshooter evidence that under certain circum- (blue-green sharpshooter) and Xyphon is often found in coastal or riparian stances natural enemies released for the fulgida (Nottingham) (red-headed habitats consisting of trees, vines and control of a pest species may attack non- sharpshooter); and other species of succulent shrubs. These unlikely forag- target species and adversely affect the leafhoppers from a different subfam- ing areas, combined with the differing populations of these organisms (Hoddle ily, Euscelidius variegatus (Kirschbaum), tribal origins of the sharpshooter and 2004b). To minimize such unwanted en- and Macrosteles fascifrons (Stål) (Aster the absence of any records indicating vironmental effects, UC Riverside scien- leafhopper). To date, the only nontarget Gonatocerus emergence from any egg tists have studied native sharpshooters species susceptible to the introduced masses may make this sharpshooter an to see if they are vulnerable to attack by agents, as determined by UC Riverside improbable alternate host for the three parasitoids native to the southeastern scientists, is H. liturata, a species that Gonatocerus parasitoids. United States, northeastern Mexico and is implicated in X. fastidiosa transmis- Additionally, sticky-card traps in the Argentina. While none of these native sion in agriculture in California and Southern California habitats occupied sharpshooters is beneficial in the sense the southwestern United States, but by G. atropunctata have yielded no cap- that they predate or parasitize insect that exists primarily in desert habitats ture of the widespread and established pests, their demise would likely trig- where parasitism by introduced my- parasitoid G. ashmeadi (Boyd, unpub- ger a cascade of nutritional effects that marid wasps is often low. The suscep- lished data). Native sharpshooter eggs could adversely affect other native spe- tible H. liturata is from the same tribe are approximately one-half the size

http://CaliforniaAgriculture.ucop.edu • OCTOBER–DECEMBER 2005 225 Parasitoid exit holes on a citrus leaf indicate Fig. 2. Population data on GWSS nymphs, adults and parasitoids gathered from citrus that adults successfully chewed through the orchards at UC Riverside. This information is invaluable in assisting our understand- egg casing and leaf epidermis to emerge. ing of pest and natural enemy phenology and population abundance over time.

of GWSS eggs, are laid singly, and are and is not reflected in the overall mean within an egg mass, and the developing embedded into the stem material rather parasitism rates for any one season. Of larva feeds within this host egg thereby than in groups just below the epider- the sharpshooter egg masses surveyed killing it. In contrast and possibly due to mal layer as is characteristic of GWSS in Riverside, 17% had at least one egg its relatively smaller size, G. fasciatus is egg masses (Boyd, unpublished data). parasitized by Gonatocerus spp. in the gregarious, and individual females de- These characteristics, coupled with the spring, compared to 30% in the summer. posit more than one egg per GWSS egg, different taxonomic placement, make In Weslaco, Texas, USDA research- yielding multiple parasitoids per host the blue-green sharpshooter an unlikely ers observed summer parasitism rates egg (Triapitsyn et al. 2003). host for any of the GWSS parasitoids. ranging from 38% to 100% of discovered Researchers at UC Riverside have GWSS egg masses with at least one egg shown that the density of female GWSS and natural enemies parasitized (G. triguttatus is the key nat- parasitoids searching for hosts has a UC Riverside scientists working ural enemy in this area). The Texas data significant effect on the sex ratio of in Southern California and USDA sci- demonstrates that GWSS populations progeny produced (Irvin and Hoddle entists working in eastern Texas col- might be successfully suppressed if 2005b). When female Gonatocerus lected phenological data on GWSS and efficacious egg parasitoids are success- parasitoids fail to encounter other ovi- G. ashmeadi populations for 2 years. fully established in California. However, positing females of the same species (Phenological data is information on given that GWSS is such an effective on a GWSS egg mass, progeny output populations with relation to the cli- vector of the X. fastidiosa pathogen, even is strongly female-biased. Laboratory mate and time of year.) In Southern highly successful suppression of GWSS experiments indicate that when the fe- California, GWSS exhibits two distinct may lead to populations that remain male does not encounter a competitor population peaks (fig. 2), the first in above acceptable levels for vineyard while ovipositing, the ratio of males to the spring when an average of 12% of managers. Regional lowering of GWSS females produced is approximately 1 GWSS eggs were parasitized, and the populations will, however, assist greatly to 8, 1 to 14 and 1 to 9 for G. ashmeadi, second in the summer when an average in all control efforts and management G. triguttatus and G. fasciatus, respec- of 19% of eggs were parasitized. This programs to curtail its spread in agricul- tively. However, increasing the num- summer figure contrasts with reported ture and the urban environment. ber of ovipositing females of the same parasitism rates of up to 100% in some species from one to two per egg mass Parasitoid biology regions, such as Florida (Triapitsyn and reduces the female offspring produced Phillips 2000). A possible explanation Mymarid wasp parasitoids that by up to 15% for all three Gonatocerus for this discrepancy in parasitism is that attack GWSS eggs are small, approxi- species. These results suggest that lo- data being collected are “snapshots” mately 0.02 to 0.06 inches (0.5 to cal mate competition affects progeny from any given season. For example, 1.5 millimeters). Parasitoid larvae pu- production, and more males are pro- the data collected from citrus grown at pate within GWSS eggs and then chew duced when females encounter other UC Riverside Agricultural Operations circular holes, through which they females of the same species that are often reflects nearly 100% parasitism emerge in search of mates and new host producing daughters with whom their rates in individual sampling events, but eggs to attack. G. ashmeadi, G. morrilli sons might mate. this level of oviposition is generally as- and G. triguttatus are solitary endopara- Laboratory studies where each sociated with low GWSS egg numbers sitoids that lay one egg per GWSS egg parasitoid was presented with eggs of

226 CALIFORNIA AGRICULTURE • VOLUME 59, NUMBER 4 Photos: Jack Kelly Clark Kelly Jack Photos:

Almond leaf scorch, left and center, is a relatively slow-spreading disease that may take many years to establish in cropping systems. Right, oleander leaf scorch is causing millions of dollars of damage to California’s freeway median strips and other ornamental plantings.

a single age showed that progeny pro- populations, and consequently increase Field survival and parasitism duction was greatest from GWSS eggs the efficacy of pest control by natural 3, 4 and 2 days old for G. ashmeadi, Most agricultural environments are enemies in agricultural systems, is un- G. triguttatus and G. fasciatus, respec- unfavorable habitats for natural ene- derstory management or the deliberate tively. Furthermore, each parasitoid mies. Herbicides can remove shelter and management of flowering plants be- species was able to utilize a range of floral resources that biological control neath orchards and vineyards (Landis et egg ages around their most preferred agents depend on, and pesticide resi- al. 2000). Sowing flowering plants (such age: 1 to 4, 3 to 6, and 1 to 3 days old dues can kill biological control agents as buckwheat, dill [Anethum graveolens for G. ashmeadi, G. triguttatus and (Gurr et al. 2003). UC Riverside scien- L.] or alyssum [Lobularia maritima L.]) as G. fasciatus, respectively. GWSS eggs tists have demonstrated that compared an understory could potentially provide that were parasitized at 8 to 10 days of to plain water, providing honey-water a food source to Gonatocerus spp. and in- age produced few parasitoid progeny and flowers of buckwheat (Fagopyrum crease GWSS biological control. The UC and those that did emerge had been esculentum Moench) significantly in- Riverside researchers found that sur- oviposited into sterile or dead host creased the longevity of both male and vival times for both sexes of G. ashmeadi, eggs lacking a GWSS embryo (Irvin female G. ashmeadi, G. triguttatus and G. triguttatus and G. fasciatus increased and Hoddle 2005a). This suggests G. fasciatus up to 94.6%, 92.4% and by up to 85.2% with softscale (Coccus that the low production of parasitoid 93.1%, respectively. These results in- hesperidum L.) excrement than with progeny in older GWSS eggs was most dicate that resource procurement may citrus foliage alone, suggesting that in likely due to the advanced stage of de- be extremely important for enhancing citrus orchards nondamaging levels of velopment of the GWSS embryos. parasitoid survival in agroecosystems. softscale may also be beneficial for en- No oviposition preferences were However, this assertion is speculative hancing parasitoid survival and could observed when GWSS eggs 1, 3 and 5 until extensive field experimentation enhance biological control of GWSS. days old were presented simultaneously is undertaken. Since resource pro- Invasive potential of GWSS to G. ashmeadi and G. triguttatus. This curement increases the longevity of suggests that these two parasitoids will female parasitoids, this may enhance GWSS has shown strong invasive attack host eggs without preference as biological control of the GWSS because potential, having become established long as eggs are of a suitable age for females that live longer may encounter in a variety of places outside its native oviposition. These choice studies indi- more GWSS egg masses and conse- range, including California, French cated that G. fasciatus preferred GWSS quently parasitize more eggs. Polynesia and Hawaii. Modeling that eggs 1 and 3 days old, while eggs 5 days UC Riverside scientists have also combines regional climate data and rel- old were not utilized. The small size of shown that the longevity of G. ashmeadi, evant biological information indicates G. fasciatus in comparison to G. ashmeadi G. triguttatus and G. fasciatus feeding that California’s premier wine-growing and G. fasciatus possibly limits the range on citrus flowers and GWSS excrement areas of Napa, Sonoma and Mendocino of GWSS egg ages available for parasit- was equivalent to that on water. This counties are vulnerable to invasion ism. This may occur because the smaller indicates that these field resources may by GWSS (Hoddle 2004a). In contrast, ovipositor of G. fasciatus may be unable not supply parasitoids with adequate states north of California, which also to pierce the chorion of older eggs as nutrition to maximize survival. One have substantial grape industries, may they harden during maturation. potential way to enhance parasitoid be too cold to harbor permanent popu-

http://CaliforniaAgriculture.ucop.edu • OCTOBER–DECEMBER 2005 227 TABLE 1. GWSS egg-mass survival, Sept. 3–9, 2003, Mo’orea, French Polynesia

GWSS eggs GWSS eggs GWSS eggs GWSS that died GWSS eggs from lations. Other climates conducive to examined parasitized eaten of natural causes* which nymphs emerged GWSS invasion — should it be acciden- ...... no...... tally introduced — include the major 2,586 (246 egg 32 444 50 2,060 wine-growing regions of New Zealand, masses studied) Australia, the Bordeaux region of % of eggs 1.24 17.17 1.93 80 France, most areas of Spain, and central * Bacterial and/or fungal infection. and southern Italy (Hoddle 2004a). Data on GWSS in Tahiti is sobering. biological control with host-specific my- Hoddle MS. 2004a. The potential adven- tive geographic range of glassy-winged Populations of this pest grew exponen- marid egg parasitoids appears to be the sharpshooter, Homalodisca coagulata and tially because there is an abundance of only feasible control strategy for provid- the grape pathogen Xylella fastidiosa: Impli- suitable native and exotic host plants; ing long-term, area-wide suppression of cations for California and other grape grow- the mild climate permits year-round this pest. This is a challenging problem ing regions of the world. Crop Prot 23:691–9. Hoddle MS. 2004b. Restoring balance: Us- breeding (in contrast to California, because, in agriculturally dependent ing exotic natural enemies to control invasive where there are just two generations, areas such as California, even excellent exotic species. Cons Biol 18:38–49. spring and summer, each year); and biological control of GWSS may not Hoover W. 2004. New invader may natural enemies are lacking, while no be sufficient to reduce substantial crop threaten crops. Honolulu Advertiser, May 14. Irvin N, Hoddle MS. 2005a. Determina- obvious competitors exist in urban or losses caused by Xylella vectored by tion of Homalodisca coagulata (Hemiptera: natural settings. Naturally occurring GWSS. In this instance, natural enemies Cicadellidae) egg ages that are suitable for parasitism of GWSS eggs is very low must form the cornerstone of integrated oviposition by Gonatocerus ashmeadi, G. triguttatus and G. fasciatus (Hymenoptera: on the French Polynesian island of pest management programs for GWSS. Mymaridae): (1) no choice tests. Biol Control Mo’orea. UC surveys indicated that less 32:391–400. than 2% of total GWSS eggs were at- Irvin NA, Hoddle MS. 2005b. The competi- tacked by parasitoids (table 1). tive ability of three mymarid egg parasitoids (Gonatocerus spp.) for glassy-winged sharp- The wasp that attacked these GWSS L.J. Pilkington and N.A. Irvin are Postdoc- shooter (Homalodisica coagulata) eggs. Biol egg masses is a platygasterid, a family toral Scholars, E.A. Boyd is Ph.D. Candi- Control 34:204–14. that does not specialize on sharpshoot- date, M.S. Hoddle is Extension Specialist Landis DA, Wratten SD, Gurr GM. 2000. ers but will parasitize various species in Biological Control, S.V. Triapitsyn is Habitat management to conserve natural en- emies of arthropod pests in agriculture. Ann of leafhoppers. The data on parasit- Principal Museum Scientist, and B.G. Rev Entomol 45:175–201. ism in Tahiti indicates that there are Carey is Staff Research Associate, all with Siebert J. 2001. Economic impact of no specialized parasitoids attacking the Department of Entomology, UC River- Pierce’s disease on the California grape in- GWSS. Only a few eggs in an egg mass dustry. California Department of Food and side; W.A. Jones is Director, USDA-ARS Agriculture Pierce’s Disease Research Sympo- are attacked, indicating inefficient and European Biological Control Laboratory, sium. p 111–6. opportunistic exploitation, and only Montpellier, France; and D.J.W. Morgan Sorensen JT, Gill RJ. 1996. A range ex- males were reared from GWSS eggs, is Entomologist, CDFA Mount Rubidoux tension of Homalodisca coagulata (Say) suggesting poor host quality because (Hemiptera: Clypeorrhyncha: Cicadellidae) Field Station, Riverside. to southern California. Pan-Pacific Entomol females did not oviposit fertilized eggs 72(3):160–1. that yield female offspring. This data References Triapitsyn SV, Morgan DJW, Hoddle MS, clearly indicates that GWSS populations [CDFA] California Department of Food Berezovskiy VV. 2003. Observations on the biology of Gonatocerus fasciatus Girault in French Polynesia are free of the pres- and Agriculture. 2003. Pierce’s disease con- trol program – report to the legislature, May (Hymenoptera: Mymaridae), egg parasitoid sures associated with natural enemies. 2003. www.cdfa.ca.gov/phpps/pdcp/docs/ of Homalodisca coagulata (Say) and Oncome- A classical biological control initiative 2002LegReport.pdf (accessed July 8, 2004). topia orbona (Fabricius) (Hemiptera: Clypeor- against GWSS has been launched and CDFA. 2005. Pierce’s Disease Geographic rhyncha : Cicadellidae). Pan-Pacific Entomol 79(1):75–6. is a cooperative enterprise between UC Information System. http://max.cdfa.ca.gov/ pdcp-gis/pdcp-gis.asp. Triapitsyn SV, Phillips PA. 2000. First record Riverside, UC Berkeley and the French Cheou D. 2002. Incursion of glassy winged of Gonatocerus triguttatus (Hymenoptera: Polynesian government. sharpshooter Homalodisca coagulata in Mymaridae) from eggs of Homalodisca co- French Polynesia. Plant Protection Service agulata (Homoptera: Cicadellidae) with notes Natural enemies and IPM Pest Alert:1. on the distribution of the host. Florida Ento- Costa HS, Blua MJ, Bethke JA, Redak RA. mol 83(2):200–3. GWSS is a major pest in California 2000. Transmission of Xylella fasitidiosa to Vickerman DB, Hoddle MS, Triapitysn SV, because of its ability to vector Xylella, oleander by the glassywinged sharpshooter, Stouthamer R. 2004. Species identity of geo- and the invasive potential of this pest Homalodisca coagulata. HortSci 35(7):1265–7. graphically distinct populations of the glassy- Gurr GM, Wratten SD, Luna JM. 2003. winged sharpshooter parasitoid Gonatocerus has been clearly demonstrated by its es- Multi-function agricultural biodiversity: Pest ashmeadi: Morphology, DNA sequences tablishment in French Polynesia, Hawaii management and other benefits. Basic Ap- and reproductive compatibility. Biol Control and Easter Island. In all invaded areas, plied Ecol 4(2):107–16. 31:338–45.

228 CALIFORNIA AGRICULTURE • VOLUME 59, NUMBER 4