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YELLOW SCALE, Aonidiella citrina (Coquillett) -- Diaspididae

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Yellow scale, also of oriental origin, is less extensively distributed than California red scale. It is known to occur in Mexico, Australia, New Guinea, Japan, Pakistan, China, India, Afghanistan, Turkey, Iran, the Soviet Union, Ethiopia, Argentina and Florida, Texas and California in the United States (Kennett et al. 1999).

In California yellow scale was a serious pest of citrus by 1880. For many years it was regarded as a separate strain of California red scale, Aonidiella aurantii (Maskell). However, cryptic morphological characters were discovered which separated the two species (McKenzie 1937). Parasitoids found to attack yellow scale in California prior to 1900 were Encarsia (= Prospaltella) aurantii (Howard), Aspidiotiphagus citrinus and Aphytis citrinus Compere [(= aonidiae (Mercet)], which were probably accidentally introduced from Japan. These parasitoids evoked excellent biological control in the San Gabriel Valley in 1889 (Craw 1891), but they were not as effective in other areas (Flanders 1956).

A Japanese race of Comperiella bifasciata was discovered in 1931, which was imported for California red scale control. This parasitoid was propagated in culture on yellow scale and colonized in the field (Smith 1942). Comperiella bifasciata was believed to give effective control within 1-3 years following colonization in the south of California, but it did not do as well in the San Joaquin Valley (Flanders 1956). A Chinese race of C. bifasciata was colonized in the San Joaquin Valley during 1948-49, which resulted in temporary control on small acreage (Flanders 1956). However, DeBach (1955) and Kennett (1973) found that the Japanese race had assumed a greater importance in the San Joaquin Valley in unsprayed orchards. Laboratory examination confirmed that the Japanese race and not the Chinese one, was the effective species. In fact, C. bifasciata collected from yellow scale in the field would not reproduce on California red scale (Rosen & DeBach 1978). Several other parasitoid species were released on yellow scale in California during 1953-1967, but only Aphytis melinus became established on yellow scale in a very restricted area (Kennett et al. 1999). DeBach et al (1978) reported that the yellow scale had become extinct throughout southern California by 1970, which as attributed to competitive displacement by California red scale and parasitism by C. bifasciata.

For greater detail on biological control effort and biology of host and natural enemies, please also see the following (Smith & Compere 1931, Nel 1933, Anonymous 1936, McKenzie 1937, Ferris 1937, 1938; Coy 1938, Flanders 1944, 1945, 1948, 1953, 1958, 1966; Compere 1955, 1961; Clausen 1956, Flanders & Gressitt 1958, Ebeling 1959, DeBach & Sundby 1963, Teran & DeBach 1963).

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

Anonymous. 1936. Success shown in uses of parasite on yellow scale. Citrus Leaves 17: 3-4.

Clausen, C. P. 1956. Biological control of insect pests in the continental United States. U. S. Dept. Agric. Tech. Bull. 1139. 151 p.

Compere, H. 1955. A systematic study of teh genus Aphytis Howard (Hymenoptera, Aphelinidae) with descriptions of new species. Calif. Univ. Publ. Ent. 10: 271-320.

Compere, H. 1961. The red scale and its natural enemies. Hilgardia 31: 173-278.

Coy, J. P. 1938. Comperiella bifasciata in San Bernardino County. Calif. State Dept. Agric. Bull. 27: 445-46.

Craw, A. 1891. Internal parasites discovered in the San Gabriel Valley; recommendations and notes. Bull. Calif. State Bd. Hort. 57: 1-7.

DeBach, P. 1955. Validity of the insecticidal check method as a measure of the effectiveness of natural enemies of diaspine scale insects. J. Econ. Ent. 48: 584-88.

DeBach, P. & R. A. Sundby. 1963. Competitive displacement between ecological homologues. Hilgardia 34: 105-66.

DeBach, P., R. M. Hendrickson, Jr. & M. Rose. 1978. Competitive displacement: Extinction of the yellow scale, Aonidiella citrina (Coq.) (Homoptera: Diaspididae) by its ecological homologue, the California red scale, Aonidiella aurantii (Mask.) in southern California. Hilgardia 46: 1-35.

Ebeling, W. 1959. Subtropical Fruit Pests. Calif. Univ. Div. Agric. Sci. Pub. 436 p.

Flanders, S. E. 1944. Observations on Comperiella bifasciata, an endoparasite of diaspine coccids. Ann. Ent. Soc. Amer. 37: 365-71.

Flanders, S. E. 1945. Coincident infestations of Aonidiella citrina and Coccus hesperidum, a result of ant activity. J. Econ. Ent. 38: 711-12.

Flanders, S. E. 1948. Biological control of yellow scale. Calif. Citrog. 34: 56, 76-7.

Flanders, S. E. 1953. Hymenopteraous parasites of three species of Oriental scale insects. Portici R. Scuola Super. di Agric. Lab. Zool. Gen e Agric. Bol. 33: 10-28.

Flanders, S. E. 1956. Struggle for existence between red and yellow scale. Citrog. 41: 396, 398, 400, 402-03.

Flanders, S. E. 1966. Unique biological aspects of the genus Casca and a description of a new species. Ann. Ent. Soc. Amer. 59: 79-82.

Flanders, S. E. & J. L. Gressitt. 1958. The natural control of California red scale in China. Calif. State Dept. Agric. Bull. 47: 23-33.

Kennett, C. E. 1973. Biological control of California red scale and yellow scale in San Joaquin Valley citrus groves--a progress report. Sunkist Newsletter No. 432. 2 p.

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.

McKenzie, H. L. 1973. Morphological differences distinguishing California red scale, yellow scale and related species. Calif. Univ. Publs. Ent. 6: 323-36.

Rosen, D. & P. DeBach. 1978. Diaspididae. In: Introduced Parasites and Predators of Arthropod Pests and Weeds. USDA Agric. Handbk. No. 480, Washington, D. C. 545 p.

Smith, H. S. 1942. A race of Comperiella bifasciata successfully parasitizes California red scale. J. Econ. Ent. 35: 809-12.

Smith, H. S. & H. Compere. 1931. An imported paraaite attacks the yellow scale. Calif. Citrog. 16: 328.

Teran, A. L. & P. DeBach. 1963. Observaciones sobre Comperiella bifasciata How. (Hymen., Encyrtidae). Rev. Agron. Noroeste Argent. 4: 5-23.