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ASH WHITEFLY, Siphonius phillyraea -- Aleyrodidae

(Contacts)

The ash whitefly, widespread in the Palearctic realm, invaded southern „alifornia in the late 1980's. By 1989, the second year after its detection, it had reached epizootic proportions. In mid autumn adult whiteflies were very conspicuous in the air all over southern California. Although several species of ash trees were its preferred host plants, when these dropped their leaves in autumn, the whiteflies invaded other plant species, and were especially troublesome on citrus, roses, etc. Because of the dispersing adult whiteflies resembling floating ash pieces, the public quickly recognized this pest vicariously.

Biological control investigators at the University of California, Riverside and in the California State Department of Food and Agriculture concluded that ash whitefly had invaded from the Old World and developed a plan to import parasitoids and predators from that part of the world. Two Encarsia spp. nr. inaron were introduced, one from central Italy and the other from Israel, the latter being supplied by Dr. Dan Gerling of the University of Tel-Aviv <PHOTO>. These parasitoids were reared in California and distributed in 13 counties of California and Arizona. Recoveries were made at all sites, but the Israel strain seemed to predominate. A coccinellid predator, Clitostethus arcuatis was also released in five California counties, but only with limited recoveries (Bellows & Paine 1990). With the establishment of these natural enemies in southern California, ash whitefly was scarcely noticeable by the public in autumn of 1990.

By 1991 the ash whitefly had spread into central and northern California, and the natural enemies have been released against it. It is expected that establishment will result in complete biological control. Whether this is possible as the whitefly spread to other parts of North America is unknown, especially as the imported natural enemies originated in subtropical or warm temperate parts of the Old World. However, temperature natural enemies are known and their acquisition should not pose any difficulty.

REFERENCES: [ Additional references may be found at: MELVYL Library ]

Bellows, T. S. & T. D. Paine. 1990. Distribution and biological evaluations of Encarsia sp. nr. inaron, parasitoid of ash whitefly, Siphonius phillyreae. Progress Rept. to the Statewide UC IPM Project, Davis, CA. 13 p.

Bellows, T.S., Jr., TD. Paine, K-Y Arakawa, C. Meisenbacher, P. Leddy, and J. Kabashima. 1990. Biological control sought for ash whitefly.

California Agriculture, 44(l): 4-6.