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The efficiencies of seven native species of eulophid parasitoids (Pnigalio katonis, Hemiptarsenus varicornis, Diglyphus isaea, D. minoeus, D. pusztensis, Chrysocharis pentheus and Neochrysocharis formosa) as biological control agents against Liriomyza trifolii in a greenhouse were evaluated based on their thermal tolerance in development and reproduction. All of them are solitary and idiobiont parasitoids, and their adults kill hosts directly by feeding on the hosts. Based upon their thermal tolerance, the species could be roughly classified into two groups, i.e., H. varicornis and N. formosa which are more adapted to high temperatures, and the other five species which are more adapted to low temperatures. In biological control, host killing by host-feeding is profitable in the release step, but becomes unprofitable in the mass-production step because it does not result directly in production of progeny. Hence, an evaluation method based on biological control efficiency (BCE) is proposed in this study as a comprehensive criterion for evaluating the efficiency of the parasitoids as biological control agents. The thermal tolerance and BCE clarified in this study revealed that D. isaea should be used in cool seasons and N. formosa in hot seasons, based on a borderline temperature of 20 to 25°C in the greenhouse.

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The polymorphic patterns of genomic DNA amplified by RAPD-PCR were detected in laboratory-cultured populations of sweet potato weevils, Cylas formicarius collected from the Southwest islands (Nansei-Shoto) of Japan. When three sets of primers, T13/T13, T05/T05 and T01/T07 were used for PCR, the polymorphic patterns of the amplified DNA were classified into nine types. Of these types, A 1 B 1 C 3 was common in all populations tested. The present study determined the useful primer sets that will enable the successful classification of sweet potato weevils based upon the polymorphic patterns of genomic DNA amplified by RAPD-PCR.