ICE PLANT SCALES
Pulvinariella mesembryanthemi (Vallot)
& Pulvinaria delottoi Gill -- Coccidae
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Two scale species, Pulvinariella mesembryanthemi (Vallot) and Pulvinaria delottoi Gill, originated in southern Africa where they attack ice plants in the families Aizoaceae and Crassulaceae. the first species, P. mesembryanthemi has a wide distribution in southern Europe, the Canary Islands, Germany and South America. Pulvinaria delottoi was first found in California in 1949 at the University of California Botanical Garden on ice plants, Carpobrotus spp., and reports followed from the Bay Area between 1949 and 1970 (Tassan et al. 1982). Frankie and Hagen (1986) note that ice plants are widely used in California as ornamental groundcovers, with the California Department of Transportation maintaining ca. 6,000 acres of ice plants along highways.
In 1971 dense populations of P. mesembryanthemi appeared in Napa, California. In 1973 a survey of ice plant along highways in Alameda County was conducted by the Calif. Dept. of Transportation (Tassan et al. 1982), and it was discovered that there were really two scale species present. Pulvinaria delottoi has one generation per year and colonizes the mature lower portions of the plant, while P. mesembryanthemi has two generations per year and favors the new terminal growth (Donaldson et al. 1978).
Dahlsten & Hall (1999) reported that by 1976 the scales were causing considerable damage to ice plants along highways, and in 1978 the Division of Biological Control at the University of California, Berkeley began a three-year biological control project funded by the State. As a result seven natural enemies of the scales were collected in southern Africa and released in California. Two coccinellid species, Hyperaspis senegalensis hottentotta Mulsant and Exochomus flavipes (Thunberg) failed to establish (Frankie & Hagen 1986). Five encyrtid wasps were liberated: Metaphycus funicularis Annecke, M. stramineus Compere, Metaphycus sp., Coccophagus cowperi Girault and Encyrtus saliens Prinsloo & Annecke. Metaphycus funicularis and M. stramineus became established throughout California and E. saliens is though to be established in northern California (Frankie & Hagen 1986). The impact of the natural enemies has now almost eliminated the need for insecticidal sprays along freeways in California (Frankie & Hagen 1986). Native encyrtids, Coccophagus spp., the exotic encyrtid Metaphycus helvolus (Compere), introduced from South Africa in the 1930's for control of black scale on citrus, and an exotic coccinellid, Cryptolaemus montrouzieri Mulsant, released for control of mealybugs on citrus also attack the ice plant scales in California.
Application of malathion bait sprays during the Mediterranean fruit fly eradication program in 1980-1982 were shown to reduce parasitism by Coccophagus lycimnia (Walker) (79%) and M. stramineus (90%) (Washburn et al. 1983, Hoy & Dahlsten 1984, Dahlsten & Hall 1999).
REFERENCES: [ Additional references may be found at: MELVYL Library ]
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.
Donaldson, D. R., W. S. Moore, C. S. Koehler & J. L. Joos. 1978. Scales threaten ice plant in Bay Area.
Frankie, G. W. & K. S. Hagen. 1986. Ecology and biology of iceplant scales, Pulvinaria and Pulvinariella in California. Calif. Dept. of Transportation, Div. of Highway Maintenance, Sacramento, California (Report No. FHWA-CA-HM-OZ). 47 p.
Hoy, J. B. & D. L. Dahlsten. 1984. Effects of malathion and Staley's bait on the behavior and survival of parasitic Hymenoptera. Environ. Ent. 13: 1483-86.
Tassan, R. L., K. S. Hagen and D. V. Cassidy. 1982. Imported natural enemies established against ice plant scales in California. Calif Agric 36:16-17.
Washburn, J. A., R. L. Tassan, K. Grace, E. Bellis, ... 1983. Effects of malathion sprays on the ice play insect system. Calif. Agric. 37(1-2): 30-32.