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Biocontrol News and Information 27(3), 47N–62N pestscience.com General News Glassy-Winged Sharpshooter K.O.’ed – First The Problems Caused by GWSS in French Polynesia Round – in French Polynesia High GWSS densities are a major annoyance for Glassy-winged sharpshooter (GWSS), Homalodisca people in French Polynesia because feeding adults coagulata, has proven to be an extraordinary and and nymphs produce astonishingly high quantities of highly invasive insect pest with a well documented watery excreta that ‘rains’ from heavily infested ability to achieve incredible population densities in trees. This makes utilization of shade trees impos- new areas when dislocated from its suite of natural sible when trying to find respite from the hot sun and enemies. This xylem feeding cicadellid is native to has earned GWSS the common local name mouche the southeast USA and northeast Mexico and in its pisseuse (‘pissing fly’). Buildings and vehicles under native and invaded ranges is a major threat to agri- infested trees are drenched with excreta to the point cultural, native, and urban landscapes because of its that water runs off structures and pools on the ability to acquire and transmit a lethal xylem- ground. Such high and continuous removal of xylem dwelling plant pathogenic bacterium, Xylella fastid- fluids by thousands of feeding nymphs and adults is iosa. This bacterium is native and widespread within thought to have had a detrimental impact on many the Americas and may exist in other countries out- plant species in French Polynesia. GWSS is sus- side of the native range having been unknowingly pected of retarding plant growth and causing imported in ornamental plants from areas with declines in fruit production, especially in mangoes endemic X. fastidiosa populations. and other fruit trees. Large numbers of flying adults are attracted to lights at night, and they invade GWSS began its range expansion in the late 1980s, houses and businesses through open windows and moving into California, USA, probably from the doors, and on occasion adults may ‘bite’ people as southeastern USA, on ornamental plants. Unparasi- they presumably probe salt glands. But the major tized egg masses on the undersides of leaves or small concern for French Polynesia is the possibility that flightless nymphs were mostly likely the original this pest could acquire and vector X. fastidiosa, inoculative propagules into California. Adult GWSS which potentially would have a disastrous impact on are extremely flighty and unlikely to stay on plants the agriculture and biodiversity of these isolated that are being subjected to vigorous handling and islands. Finally, the immense propagule pressure transport. Inordinate densities of GWSS developed emanating from French Polynesia represents a in California and began to spread rapidly out of major invasion threat to other South Pacific coun- southern California where populations were origi- tries. Adult H. coagulata have been found on planes nally highly localized. Despite widespread originating from Tahiti arriving in Japan and in insecticide use in ornamental nurseries to produce Australia. uninfested plants for sale and citrus orchards to reduce immigration into vineyards and other crops, Factors Promoting Establishment, Proliferation and Spread immense propagule pressure still resulted and Cali- fornia was most likely the source for GWSS entering The rapid proliferation and spread of H. coagulata in Tahiti (Society Islands of French Polynesia) in 1999, French Polynesia can be explained by four main fac- and Hawaii in 2004. Easter Island (GWSS detected tors: First, environmental conditions in these in 2005) was probably infested with material origi- tropical islands are ideal for reproduction. Moderate nating from French Polynesia. temperatures and high rainfall in some areas ensure ideal breeding conditions year round on abundant Distribution in French Polynesia native and exotic host plants. We estimate that in Tahiti, there are 6–8 overlapping H. coagulata gen- In French Polynesia, GWSS reproduced and spread erations a year, compared to 2–3 generations in very rapidly and is currently found in almost all California and northern-central Florida (USA). In islands in the Society Island group (Tahiti [invaded California, cold winters retard egg production and in 1999], Moorea [2002], Tahaa, Raiatea, Huahine, egg laying in H. coagulata. Consequently, cold tem- Bora Bora, Maupiti [2001–2005]) and has also been peratures do not inhibit reproduction by H. recorded in Nuku Hiva in the Marquesas (2004), and coagulata in French Polynesia. Instead, reproductive in Tubuai and Rurutu (both 2005) in the Australs potential appears to be more strongly influenced by (2005). It is unknown if GWSS is in the Tuamotu wet and dry seasons, with greater populations being group of islands. Widespread and rapid movement of observed during wet periods. GWSS in French Polynesia most likely occurred via unregulated movement of plants that carried GWSS Second, our surveys in French Polynesia indicate egg masses or nymphs between islands and island that there appear to be no effective natural enemies groups by plane and boat. GWSS populations in regulating H. coagulata populations. Surveys of H. Tahiti and Moorea reached densities far exceeding coagulata egg masses on Tahiti and Moorea in 2003 those observed in its native range or even California showed very low levels of parasitism; less than 5% of where populations were much greater than those the egg masses were attacked by parasitoids. The observed in the southeastern USA. parasitoid species that was reared from H. coagulata Are we on your mailing list? Biocontrol News and Information is always pleased to receive news of research, conferences, new products or patents, changes in personnel, collaborative agreements or any other information of interest to other readers. If your organization sends out press releases or newsletters, please let us have a copy. In addition, the editors welcome proposals for review topics. 48N Biocontrol News and Information 27(3) egg masses was an unidentified encyrtid. Female entists with the French Polynesian Agricultural parasitoids only exploited 1–3 eggs in an attacked Research and Plant Protection departments guided egg mass (egg masses typically contain on average the development of the GWSS biological control around 7–10 eggs) and only male eggs were ovipos- programme. ited suggesting that parasitism was opportunistic and that H. coagulata eggs were assessed to be of low Determining the Risk Posed by GWSS Egg Parasitoids to quality as only haploid male eggs were laid. This Native Insects obvious dearth of effective indigenous natural ene- mies is highly likely to have facilitated the An over-riding requirement for classical biological establishment and rapid spread of H. coagulata in control of GWSS in French Polynesia is safety and a French Polynesia. demand for minimal to non-existent non-target impacts. Particular attention is being paid to the Third, H. coagulata may pose a substantial risk to identification and assessment of risk to non-target generalist arthropod predators on invaded islands in native fauna, in particular native cicadellids. As with French Polynesia. Controlled feeding experiments many small isolated islands, French Polynesia is have revealed that some species of spiders can be extremely susceptible to invasions by exotic organ- killed following predation on H. coagulata. Mortality isms. Unfortunately, French Polynesia has a poor in both the native crab spider Misumenops mello- track record in biological control safety and pro- leitao and the pan-Pacific orb-weaving spider gramme efficacy. Consequently, this pest control Cyrtophora moluccensis appeared to result from technology is viewed with scepticism by many offi- lethal intoxication, although no form of chemical cials managing invasive species in French Polynesia. defence has been reported in H. coagulata. In both The most egregious example of a ‘biological control spider species, approximately half of all spiders that disaster’ in French Polynesia was the unintentional attacked individual H. coagulata nymphs or adults extirpation of native Partula snails on many islands died. As H. coagulata populations increase in size by the predatory snail, Euglandina rosea, which was and range on invaded islands in French Polynesia, released for the biological control of the giant African this insect will be increasingly encountered by these land snail, Achatina fulica, in 1977. Biological con- and other arthropod predators, raising the possi- trol programmes for arthropod pests are bility of population-level impacts on susceptible consequently being held accountable for greater predator species. levels of safety than has been required in the past, and determination of host specificity and assessment of expected levels of safety and impact are emerging Fourth, the cicadellid fauna of French Polynesia is as rapidly developing new areas in classical biolog- impoverished with few known native species and a ical control of arthropod pests. substantially greater number of exotic species that have established accidentally. Consequently, compe- Gonatocerus ashmeadi is a specialized parasitoid tition by other proconiine cicadellids is non-existent that attacks cicadellid eggs in the tribe Proconiini. as this tribe within the Cicadellidae is unique to the Hence introduction of G. ashmeadi in French Poly- Americas and lacks naturally-occurring representa- nesia is considered low risk for native