GWSS in FP - Nuisance

Public annoyances
Following its arrival, GWSS proliferated and spread rapidly in French Polynesia. In 2003, its abundance in Tahiti was ~1000 times higher than in its natural range in Florida and at least 10 times higher than in California. This enormous density is common for many successful invasive species once established outside of their home range and free from population regulation by natural enemies (e.g., parasites, predators, and pathogens).
GWSS egg-masses on Cordyline leaves in Papenoo	GWSS on a Pandanus in Papeete
The humid tropical climate with moderately high year round temperature and high rainfall in French Polynesia has proven ideal for year round reproduction by GWSS. It is estimated that in Tahiti, there are 6 to 8 overlapping GWSS generations a year, compared to 2 to 3 generations in California and Florida. French Polynesia also offers numerous potential exotic and native host plants for feeding and reproduction. Our initial surveys in French Polynesia indicated that there were no effective natural enemies regulating GWSS populations. Moreover, the invasion might have been favoured by reduction of generalist arthropod predation due to intoxication after consuming GWSS. Controlled feeding experiments have revealed that some species of spiders can be killed following predation of GWSS. Finally, invasion by GWSS may also have been favoured because of weak competition by other insects (native and exotic).
Agricultural and ecological pressure
Such high and continuous removal of xylem fluids by thousands of feeding nymphs and adults is thought to have had a detrimental impact on many plant species in French Polynesia. GWSS is suspected of retarding plant growth and causing declines in fruit production, especially mangoes and other fruit trees. GWSS excreta on leaves and fruits decrease the commercial values of agricultural products and may cause more rapid deterioration of fruit on trees.	GWSS excreta on citrus fruit
Xylella fastidiosa bacterium in xylem	GWSS is also a major threat to agricultural, native, and urban landscapes because of its ability to acquire and transmit a lethal xylem-dwelling plant pathogenic bacterium, Xylella fastidiosa. Infection of plants with this bacterium blocks the xylem resulting in a variety of leaf-scorch diseases, which can lead to the death of plants. In California, this disease is most devastating for grapes, a crop worth approximately US$ 5 billion per year. The major concern for French Polynesia is the possibility that this pest could acquire and vector X. fastidiosa, which potentially, would have a disastrous impact on agriculture and native plant biodiversity of these isolated islands.
Social pressure
Finally, high GWSS densities are a major annoyance for people in French Polynesia because feeding adults and nymphs produce astonishingly high quantities of watery excreta that “rains” from heavily infested trees. This makes utilization of shade trees impossible when trying to find respite from the sun. At night, huge numbers of flying GWSS adults are attracted to lights, invading houses and business, and causing significant nuisance to people. In some instance, GWSS are alleged to bite people after landing on exposed skin and presumably probing salt glands.
	GWSS by night in Paea (June 2005)

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Jérôme N. Petit © juillet 2006 - Gump station