M. alberti stinging Coccus hesperidium, soft brown scale.
Note: wasp is only 1.5-2 mm long.
PHOTO: Mike Rose

Metaphycus alberti
Hymenoptera: Encyrtidae

by Steve Stauffer, Integrated Pest Management, Cornell Unversity, Ithaca, NY

Metaphycus alberti (Howard) was originally brought to California from Australia in 1898 by Albert Koebele, whose earlier entomological investigations of that continent led to the successful biological control of the cottony cushion scale (DeBach and Rosen, 1991). The new parasite was subsequently named for Koebele by L.O. Howard (Howard, 1898).

Appearance

M. alberti is a member of the asterolecanii (= hederaceus) group of Metaphycus, with two segmented maxillary and labial palpi (Annecke, 1981). M. alberti is distinguished from other members of the asterolecanii group (for instance, M. helvolus) by ocelli that form an acute triangle, and mid-tibia that are significantly longer than their ovipositor in females.

M. alberti is very small - 1.5-2 mm long, and males are noticeably darker than females.

Habitat

Currently, M. alberti is a rather rare natural enemy of Coccus hesperidium (soft brown scale). Indoors, in locations where it has become established through innoculative biological control programs, it may be found in the vicinity of plants attacked by its host in greenhouses, conservatories and atriums . Plant species preferred by C. hesperidium are evergreen, tropical and semitropical species of plants, although it attacks nearly every type of plant except grasses.

Pests Attacked (Host Range)

This species has not been reported in the literature from other hosts, and therefore appears to be specific to C. hesperidum. It is known to attack C. hesperidum between the crawler and the adult stages, preferring young scale from 1 to 1.5 mm long, but successfully attacking much larger hosts as long as they are not reproducing.

Koebele's original material was reared from C. hesperidum collected in the Sydney area.

The parasite was apparently colonized in Riverside, California, around the turn of the century. It was subsequently recovered from C. hesperidum by Timberlake during 1911 and 1912 . Despite all of the subsequent sampling of C. hesperidum in southern California, M. alberti has not been reported from North America since Compere reared it from C. hesperidum in 1922 . At present, M. alberti is known only from California, South Africa, and Australia.

Life Cycle

Biological studies of M. alberti have never been conducted. Laboratory rearing experience with this species suggests that it has a life cycle similar to M. luteolus or M. flavus  - two species with which it also shares many morphological and behavioral features.

M. alberti is biparental, develops gregariously [more than one egg in the same host], and has a short developmental period, emerging in as little as 12 days after oviposition. It is easily reared on midsize, immature C. hesperidum utilizing methods developed by Bartlett (Bartlett and Lagace, 1961), Reed et al. (Reed, et al., 1968), Ingle et al. (Ingle, et al., 1975), and others.

Relative Effectiveness

Metaphycus alberti is an active searcher, has a short, uncomplicated life cycle, and is consistently able to overcome egg encapsulation and develop successfully in Texas populations of C. hesperidum (Stauffer, 1996). It has been used several times to control entrenched populations of C. hesperidum in interior plantscapes. In each case, it provided excellent, long-lasting control.

Pesticide Susceptibility

This parasite is easily killed by pesticides. No pesticide tolerant strains are known.

Commercial Availability

Not commercially available, although there is some interest among commercial insectaries.

References

Annecke, D. P., and Mynhardt, M. J., 1981. The species of the Astrolecanii-group of Metaphycus Mercet (Hymenoptera: Encyrtidae) from South Africa with notes on some extralimital species. Jour. Ent. Soc. So. Africa, 44(1):1-68.

Annecke, D. P., 1964. The encyrtid and aphelinid parasites (Hymenoptera: Chalcidoidea) of soft brown scale, Coccus hesperidum Linnaeus (Hemiptera: Coccidae), in South Africa: Entomology Memoirs, Dept. of Ag. Tech. Services, Government Printer, Rep. of So. Africa, Pretoria, 47 pp.

Bartlett, B. R., and Lagace, C. F., 1961. A new biological race of Microterys flavus introduced into California for the control of lecaniine coccids, with an analysis of its behavior in host selection. Ann. Ent. Soc. Amer., 54: 222-227.

DeBach, P., and Rosen, D., 1991. Biological Control by Natural Enemies: Cambridge University Press, Cambridge, England, 440 pp. Howard, L. O., 1898. On some new parasitic insects of the subfamily Encyrtinae. Proc. U.S. National Museum, 21: 231-248.

Ingle, S. J., Hart, W. G., Garza, M. G., and Lara, P., 1975. A modified cage and procedure for rearing parasites of brown soft scale. Jour. Econ. Ent., 68: 355-357.

Reed, D. K., Hart, W. G., and Ingle, S. J., 1968. Laboratory rearing of brown soft scale and its hymenopterous parasites. Ann. Ent. Soc. Amer., 61: 1443-1446.

Stauffer, R. S., 1996. The biological control of brown soft scale Coccus hesperidum L. (Homoptera: Coccidae) in interior plantscapes [Master of Science]. Texas A&M University, 106 pp.

Stauffer, R. S. and Rose, M. 1997. Biological Control of Soft Scale Insects in Interior Plantscapes in the USA. In Soft Scale Insects - Their Biology, Natural Enemies and Control. Y. Ben-Dov and C.J. Hodgson (Eds.). Elsevier Science B.V.

Timberlake, P. H., 1916. Revision of the genus Aphycus. Proc. U.S. National Museum, 50: 587-639.

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