This parasitic wasp, Gonatocerus triguttatus, lays its own eggs inside those of the glassy-winged sharpshooter. Click image for additional information.

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Searching South America for Sharpshooter Biocontrols

Two tiny wasps from South America are among the top candidates as biological controls for the glassy-winged sharpshooter, a pest that attacks citrus crops and has caused problems for grape growers in California.

The pest has bred in large numbers in southern California, a region that lacks most of the insect's natural enemies. Agricultural Research Service entomologist Walker Jones at the Kika de la Garza Subtropical Agricultural Research Center in Weslaco, Texas, is leading an international effort to find nonchemical methods to stop this invasive leafhopper.

Sections of South America, particularly Chile and Argentina, have climates that are very similar to those of some of California's prime agricultural areas. Some of those sections of South America also have sharpshooters that are close relatives of the glassy-winged sharpshooter. Given the similarities to California climates, South American biological control agents should already be pre-adapted to the Golden State, according to Jones.

In a 2002 search of northern Chile and northwestern Argentina, Jones and colleagues found more than a half-dozen such natural enemies of South American sharpshooters. Jones' main collaborators were Guillermo Logarzo, with the ARS South American Biological Control Laboratory in Hurlingham, Argentina, and Eduardo Virla, with an Argentine agency called PROIMI (Planta Piloto de Procesos Industriales Microbiológicos), which does work similar to that of ARS, the U.S. Department of Agriculture's chief scientific research agency.

Their top two biological control prospects have turned out to be tiny wasps, Gonatocerus tuberculifemur and G. metanotalis. These wasps have been known to attack the eggs of a South American sharpshooter, Tapajosa rubromarginata. This insect is very similar to--albeit slightly smaller than--its glassy-winged cousin.

The scientists also brought back seven other wasps, all of which are stingless, harmless to humans, and only attack sharpshooter eggs. Jones considers the two Gonatocerus species the most promising, in part because much is known about them. They are also abundant in South America.

Read more about this research in the September issue of Agricultural Research magazine, available online.