CEREAL LEAF BEETLE
Oulema melanoplus (L.) -- Chrysomelidae
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A native pest of cereals in Europe, cereal leaf beetle was first recorded from Berien County, Michigan in 1962. According to Haynes & Gage (1981), damaging populations in the area were probably present since the 1940's. Expansion of the area infested by the cereal leaf beetle occurred rapidly and the current range extends through much of the Midwestern states to the East Coast. Strict interstage quarantines and treatment of potentially infested bales of hay and grain were enforced. Eradication efforts continued for about seven years, but were finally abandoned when the spread of the beetle obviously could not be halted. Probably widespread public opposition to the spray program influenced this decision.
The cereal leaf beetle has one generation per year and overwinters as unmated adults (Castro et al. 1965). With the spread of the beetle out of control, research was initiated in several areas, including sterile male techniques, behavioral control by means of attractants and biological control by means of imported natural enemies. Clausen (1978) summarized the biological control program. Initiated in 1963, the search for natural enemies concentrated in France, Italy and Germany. From 1964 to 1967 five parasitoids were imported and four to become established were Tetrastichus julis (Walk.), Diaparis carinifer (Thomsen), Lemophagus curtus Tow. and Anaphes flavipes (Foerster) (Haynes & Gage 1981).
Mass releases of A. flavipes were conducted in the absence of more efficient natural enemies. Releases were made in Indiana in 1966 and the parasitoid was recovered at most sites later in the same season (Anderson & Paschke 1968). As the beetle was not easily reared in the laboratory, cultures of the parasitoid were maintained on beetles collected in the field. These beetles were also used in the screening of wheat, oats, and barley lines and varieties for resistance against the beetle. A parasitoid nursery was established in Niles, Michigan for the redistribution of parasitoids reared on field-infested populations.
Populations were observed to decline since 1971, with causes for the decline being attributed to a combination of such factors as weather-related mortality, mortality due to introduced parasitoids, genetic changes in beetle populations and changes in overwintering habitat (Haynes & Gage 1981). Although sporadic outbreaks may require treatment, populations of the beetle seem to have generally abated. This history suggests that immigrant pests, after an initial period of explosive expansion, may follow a pattern of adaptation within the agroecosystem that results in an equilibrium state not as detrimental to the crop.
REFERENCES: [Additional references may be found at: MELVYL Library ]
Anderson, R. C. & J. D. Paschke. 1968. The biology and ecology of Anaphes flavipes (Hymenoptera: Mymaridae), an exotic egg parasite of the cereal leaf beetle. Ann. Ent. Soc. Amer. 61: 1-5.
Castro, T. R., R. F. Ruppel & M. S. Gomulinski. 1965. Natural history of the cereal leaf beetle in Michigan. Michigan State Univ. Agr. Expt. Sta. Quart. Bull. 47: 623-53.
Clausen, C. P. 1978. Introduced Parasites and Predators of Arthropod Pests and Weeds: A World Review. U. S. Dept. Agric., Agric. Handbk. 480. 545 p.
Haynes, D. L. & S. H. Gage. 1981. The cereal leaf beetle in North America. Ann. Rev. Ent. 26: 259-87.