Aleurothrixus floccosus (Maskell) -- Aleyrodidae
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Principally a pest of citrus and widely distributed in the West Indies, Central and South America, the origin of the woolly whitefly was not known (Clausen 1978). The platygasterid Amitus spiniferus (Brethes) and two aphelinids, Eretmocerus paulistis Heimpel and Cales noacki De Santis, were used with success in biological control attempts in France, Chile and northwestern Mexico (Luck 1981). In backyard citrus of San Diego, California, the woolly whitefly first became a pest in 1966 (DeBach & Rose 1976). Previously DeBach observed that the whitefly was not particularly troublesome on mainland Mexico and A. spiniferus, E. paulistis and a Encarsia sp. were introduced in 1967 to the area of San Diego (DeBach & Rose 1976). Amitus spiniferus and E. paulistis became established and began to eliminate the whitefly. However, later in 1969 the California Department of Food and Agriculture began an eradication program against this whitefly, using insecticides. Biological control attempts immediately ceased in California, but were continued in Mexico just below the U. S. border (DeBach & Rose 1976). A small number of the two parasitoids which showed promise in San Diego were colonized in Tijuana in 1969. In one year by transferring twigs from two nursery trees with parasitized whitefly, >27,000 parasitoids were distributed around Tijuana. A third species of parasitoid, Cales noacki from Chile was also introduced, and by late 1970 all three parasitoids were well established, producing an obvious biological control success (Anonymous 1971, Bennett et al. 1976, Dahlsten & Hall 1999).
Biological control resumed in San Diego in 1971 when eradication efforts failed (DeBach & Rose 1976). The infested area had not covered around 200 square miles, and the University of California, Riverside and California Dept. of Food and Agriculture cooperated in releasing parasitoids which were collected in Tijuana and mainland Mexico, Chile and Brazil. Successful colonizations occurred at all release sites in 1972. Although the woolly whitefly continued to spread in California, by 1973 biological control had succeeded in San Diego and Tijuana (DeBach & Rose 1976).
When the Japanese beetle, Popillia japonica Newman, was found in San Diego in 1973, an immediate eradication program was launched against it. Studies were made to investigate the effects of three chemical pesticides (carbaryl, chlordane and dicofol) on the natural enemies of the whitefly (DeBach & Rose 1977). Dicofol was used for mite control because of the disruption caused by the insecticides. It was learned that the pesticide treatments definitely disrupted biological control of the whitefly. Before treatments began the two parasitoids, A. spiniferus and C. noacki were generally distributed and other citrus pests were under good biological control. After treatment woolly whitefly populations increased dramatically, being almost 1,200 times higher in treated areas than in untreated areas (Dahlsten & Hall 1999). Populations of citrus red mite, Panonychus citri (McGregor), and purple scale, Cornuapis (=Lepidosaphes) beckii (Newman) also increased (DeBach & Rose 1977). Parasitoids were observed to return to the previously treated areas following cessation of eradication efforts (Dahlsten & Hall 1999).
Dahlsten & Hall (1999) report that the side effects of eradication programs are generally not well documented, partly because most programs are in heavily populated environments. Eradication projects employing broad spectrum insecticides provide unique opportunities to study biological control in metropolitan areas. Eradication of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) during 1980-82 employed malathion bait sprays in northern California, and this resulted in the disruption of biological control of various arthropods in the metropolitan areas (Dreistadt & Dahlsten 1986). There were more mites, aphids and whiteflies in sprayed than in unsprayed areas (Troetschler 1983). The reduced control of other arthropods, such as walnut aphid, Chromaphis juglandicola (Kaltenbach) and black scale, Saissetia oleae (Bernard) was attributed to the effects of the bait sprays on natural enemies (Ehler & Endicott 1984). Iris whitefly, Aleyrodes spiraeoides Quaintance, parasitoids were also found to be significantly more susceptible to malathion sprays than were the whiteflies and parasitism was significantly lower on plants in the sprayed areas (Hoelmer & Dahlsten 1988).
The above mentioned parasitoids were introduced to Malaga, Spain in 1970, but only C. noacki became established. Complete biological control of woolly whitefly was attained in 1974 (Greathead 1976). Similar results were obtained after C. noacki was introduced to France in 1971, Reunion in 1976, Portugal in 1978, Sicily in 1983 and Hawaii in 1981 and Italy in 1982, the latter having both C. noacki and A. spinferus present. Cales noacki appeared in Morocco also, where control was obtained (Kennett et al. 1999).
REFERENCES: [ Additional references may be found at: MELVYL Library ]
Anonymous. 1971. A big bet on biological control. Citrograph 56: 315-16, 327.
Beingolea, G. O. 1959. El problema de la "mosca blanca lanuda" de los cítricos en el Peru Aleurothrixus floccosus (Homop.: Aleurodidae). Rev. Peru. Ent. Agric. 2: 65-8.
Bennett, F. D., P. Cochereau, D. Rosen & B. J. Wood. 1976. Biological control of pests of tropical fruits and nuts. In: C. B. Huffaker & P. S. Messenger (eds.), Theory and Practice of Biological Control. Academic Press, New York & London. 788 p.
Clausen, C. P. 1978 (ed.). Introduced parasites and predators of arthropod pests and weeds: A world review. USDA ARS Agriculture Handbook No. 480. 545 p.
Dahlsten, D. L. & R. W. Hall. 1999. Biological control of insects in outdoor urban environments. . In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p.
DeBach, P. & M. Rose. 1976. Biological control of woolly whitefly. Calif. Agric. 30(5): 4-7.
DeBach, P. & M. Rose. 1977. Environmental upsets caused by chemical eradication. Calif. Agric. 31(7): 8-10.
DeBach, P. & S. C. Warner. 1969. Research on biological control of whiteflies. Citrograph 54: 301-03.
Ehler, L. E. & P. C. Endicott. 1984. Effect of malathion-bait sprays on biological control of insect pests of olive, citrus, and walnut. Hilgardia 52(5): 1-47.
Greathead, D. J. 1976. A review of biological control in western and southern Europe. Tech. Comm. No. 7, CIBC. Commonw. Agr. Bur., Farnham Royal, Slough, England. 182 p.
Hoelmer, K. A. & D. L. Dahlsten. 1988. Non-target effects of malathion bait spray on iris whitefly (Aleyrodes spiraeoides Quaintance) (Homoptera: Aleyrodidae) and its parasitoids in Northern California. Environ. Ent. (in press).
Kennett, C. E., J. A. McMurtry & J. W. Beardsley. 1999. Biological control in subtropical and tropical crops. In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p.
Luck, R. F. 1981. Parasitic insects introduced as biological control agents for arthropod pests. p. 125-284. In: D. Pimentel (ed.), CRC Handbook of Pest Management in Agriculture Vol. II. CRC Press, Inc. Boca Raton, Florida. 501 p.
Troetschler, R. G. 1983. Effects on nontarget arthropods of malathion bait sprays used in California to eradicate the Mediterranean fruitfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Environ. Ent. 12: 1816-.
Watson, J. R. 1915. The woolly whitefly (Aleurothrixus howardi) in Florida citrus plantations. Fla. Agric. Expt. Sta. Bull. 126: 81-102.
Yothers, W. W. 1919. The Woolly white fly in Florida citrus groves. U. S. Dept. Agric. Farmers' Bull. 1011. 14 p.