Biological Control Ofthe Glassy-Winged Sharpshooter
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FACT SHEET BIOLOGICAL CONTROL OF THE GLASSY-WINGED SHARPSHOOTER IN FRENCH POLYNESIA GUMP STATIONMOOREA INDEX: BIOCONTROL PROGRAM: SOMMAIRE: Location: French Polynesia THE GLASSY-WINGED SHAR- 2 SHOOTER HOMALODISCA VITRIPENNIS Period: June 2004—May 2006 Target: Glassy-winged sharpshooter (Homalodisca vitripennis) GLASSY-WINGED SHARPSHOOTER 3 DEMOGRAPHY Method: Biological control THE PARASITOID GONATOCERUS 4 Objective: Reduce the pest population ASHMEADI Assess the collateral risk to native fauna RISK ASSESSMENT ON NATIVE 5 Control agent: Egg parasitoid (Gonatocerus ashmeadi) CICADELLIDS Bases: Gump Station, University of California Berkeley (Moorea) PARASITOID INTRODUCTION 4 Rural Development Service of French Polynesia (Papara) Sponsors: French Polynesia, Ministry of Agriculture MONITORING THE PARASITOID 5 University of California, Berkeley and Riverside EFFICIENCY Secretariat of the Pacific Community PARASITOID IMPACT ON THE 6 GLASSY WINGED SHARSHOOTER Conventions: 4.0328/PR/MAE/SDR and 6.0655/PR/MAE/SDR BIOLOGICAL CONTROL OF THE GLASSY-WINGED SHARPSHOOTER Page 2 THE GLASSY-WINGED SHARPSHOOTER (GWSS) The glassy-winged sharpshooter Florida (GWSS) Homalodisca vitripennis Mexico (Germar) [formerly H. coagulata (Say)] (Hemiptera : Cicadellidae) is an invasive species in French Poly- nesia. Adults and nymphs of GWSS are xylophagous (feed on sap). This pest can consume up to 100 times French Polynesia Easter its body weight per day. As a result, Island the pest excretes copious amounts of watery liquid which is continu- World distribution of the GWSS ously discharged from heavily in- fested trees. GWSS has thus earned the common local name GWSS adult “mouche pisseuse“ (pissing fly). Glassy-Winged Sharpshooter GWSS can feed on more than 150 Nuisances plant species in 34 plant families. • is an invasive species in GWSS females lay eggs on the Following its arrival, GWSS proliferated and spread rapidly the Pacific region undersides of leaves. The life cycle in French Polynesia. In 2003, its abundance in Tahiti was of GWSS takes approximately 4 ~1,000 times higher than in its natural range in Florida. • originated from Florida/ months. The humid tropical climate with moderately high year round Mexico temperature and high rainfall, and the absence of natural has invaded 10 islands in Distribution specific enemies in French Polynesia offered ideal condi- • French Polynesia GWSS is native to the southeast tions for massive year round reproduction by GWSS. U.S.A. and northeast Mexico. In the GWSS is a major agricultural, environmental and social • is spread by the transpor- pest. Such high removal of xylem fluids by thousands of late 1980's, this pest invaded Cali- tation of plants contain- feeding nymphs and adults is suspected to retard plant fornia via transport of ornamental ing eggs growth and to cause decline in fruit production. GWSS is plants containing eggs. GWSS then also a vector of a lethal plant pathogenic bacterium Xylella invaded Tahiti in 1999 and Hawaii • consumes up to 1, 000 fastidiosa. Moreover, the GWSS is a public annoyance in in 2004 (probably from California). times its body weight/day FP both because of the rain from highly infested trees and It was detected in Easter Island in because the insects tend to congregate around light • is an agricultural, environ- 2005 (probably from French Poly- sources at night. mental and social nui- nesia). sance Life cycle of the Glassy-Winged Sharpshooter GWSS abundance in Tahiti in 2005 months FACT SHEET Page 3 GLASSY-WINGED SHARPSHOOTER DEMOGRAPHY IN FRENCH POLYNESIA In French Polynesia, GWSS reproduced and spread very rap- Abundance Tahiti idly and is currently found on almost all islands in the Society 200 Island group (Tahiti invaded in 1999, Moorea in 2002, Tahaa, Raiatea, Huahine, Bora Bora, Maupiti in 2001-2005) and has 150 also been recorded on Nuku Hiva in the Marquesas (2004), Moorea on Tubuai and Rurutu (both 2005), and in the Australs (2005). It is unknown whether or not GWSS has arrived in the Tuamotu or the Gambier group of islands (except Rangiroa). 100 Raiatea Huahine GWSS abundance within each island was significantly corre- 50 lated with its invasion date (the last islands invaded have the Bora Bora Tahaa lowest densities). Abundance in Leeward islands, Marquesas and Australs was 10 times lower than in Tahiti and Moorea. 0 GWSS populations were mainly concentrated in urbanized 01234567 areas of each island. Years after invasion GWSS abundance (nymphs collected per minute of sampling with a sweep net on Hibiscus), related to the date of invasion (1) (2) (1) GWSS dispersal in French Polynesia (2) G W S S a b u n d a n c e (nymphs collected per minute of sampling with a sweep net on Hibiscus, cross for absence) in Tahiti in April 2005 (3) in Raiatea (Leeward Islands) in June 2005 (4) in N u k u H i v a (Marquesas) in November 2005 Caption describing picture or graphic. (3) (4) BIOLOGICAL CONTROL OF THE GLASSY-WINGED SHARPSHOOTER Page 4 PARASITOÏD GONATOCERUS ASHMEADI The egg parasitoid, Gonatocerus ash- meadi Girault (Hymenoptera : Mymari- Gonatocerus ashmeadi dae), is a natural enemy of GWSS. It is native to south-eastern USA and north-eastern Mexico where it is a • is harmless to humans common and very effective parasitoid and animals (it doesn’t associated with GWSS. Gonatocerus sting) ashmeadi attacks the eggs of GWSS. • is not an agricultural pest Female G. ashmeadi lay one egg in- (it feeds on nectar) side a single GWSS egg. The parasi- toid larva grows inside the GWSS egg • is extremely specialized (it consuming its contents. After approxi- attacks only one tribe of mately 12 days of development, an cicadellids) adult parasitoid emerges from the is well adapted to the parasitized GWSS egg. • Caption describing picture or graphic.tropical climate and is easy to mass rear Gonatocerus ashmeadi adult • develops 3 to 4 times (above) faster than GWSS • is strictly dependant on GWSS eggs for its repro- duction Gonatocerus ashmeadi life days cycle (on the left) (1) Parasitoids used for the biocontrol program in French Polynesia were reared in a secure quarantine facility at the Entomological Laboratory of the Rural Development Service in Papara ( Tahiti). Mass production of G. ashmeadi involved four permanent set ups: (1) a plant nursery to produce host plants for GWSS to lay eggs on; (2) a GWSS colony used to produce eggs for parasitoids to attack (3), and (4) a parasitoid colony. (4) (2) (3) FACT SHEET Page 5 RISK ASSESSMENT ON NATIVE CICADELLIDS An primary requirement for classi- pelago (16 native species for G. ashmeadi. cal biological control of GWSS in and 9 exotic). Also, 9 spe- Moreover, all known hosts French Polynesia is the necessity to cies have been collected in of G. ashmeadi are cicadel- minimize non-target impacts. Par- the Marquesas and 7 spe- lids of moderately large size ticular attention has been paid to cies in the Australs. Most of (1.5-2cm in length) which the identification and assessment the native species collected lay fairly large eggs (2.5- 3 of risk to non-target native fauna, are new to science and in mm in length) that occur in in particular, native Cicadellids. need of detailed studies. clusters or masses. All ci- Surveys and preparation of an in- Gonatocerus ashmeadi is a cadellids found in Society ventory of native species collected specialized parasitoid that Islands are small and most from French Polynesia have been attacks cicadellid eggs in of them appear to lay their initiated to reduce the possibility the tribe Proconiini. Thus, eggs on herbs, or singly on that overlooked indigenous species the introduction of G. ash- leaves and not in clusters or could be inadvertently put at risk. meadi in French Polynesia is masses. Only five species of cicadellids had considered low risk for na- Therefore, native cicadellids been recorded from Society Islands tive cicadellids as surveys of French Polynesia are before our studies (3 native spe- have clearly indicated that considered to be at low risk Compared sizes of GWSS (above) cies and 2 exotic). During our sur- there are no indigenous of attack by the parasitoid and 2 native cicadellids (below) veys, 25 species from 12 genera representatives in this tribe G. ashmeadi. have been collected in this archi- that may be potential hosts Only 5 cicadellid species had been described from Society Islands, 25 species were recorded during this program (2) (1) Native cicadellids of Society Islands. (1) (2) Inventory sites in Tahiti, (3) Bora Bora, (4) Marau and (5) in Marquesas (3) (4) (5) BIOLOGICAL CONTROL OF THE GLASSY-WINGED SHARPSHOOTER Page 6 INTRODUCTION OF THE PARASITOID GONATOCERUS ASHMEADI Available data on native species and potential non- Parasitoid human-mediated target impacts were presented to the Council of spread in French Polynesia: Ministers of French Polynesia in April 2005. The Council decided that release of G. ashmeadi from quarantine for liberation and establishment in the field should be initiated in May 2005. The Commis- sion of Natural Monuments and Sites of French Polynesia gave its approval for releases in Society Islands in April 2005, in the Marquesas in February 2006 and in the Australs in April 2006. The first release of G. ashmeadi began on May 2, 2005 at experimental sites in Papenoo, on the north end of Tahiti. On September 2005, releases of G. ashmeadi began on the whole island of Tahiti. A total of 14,000 parasitoids were released in 27 sites located around the island. Parasitoids estab- lished successfully at release sites and reproduced rapidly in the wild. A short time after its introduction in Tahiti, G. ash- meadi had spread in every island of French Polyne- sia infested by the GWSS, through the uncontrolled Gonatocerus ashmeadi transportation of plants containing parasitized was spread through the eggs of GWSS, from September 2005 to April uncontrolled 2006.