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.

The indigenous endoparasitic koinobiont Dacnusa nipponica is considered a potential parasitoid of the exotic leafmining fly Liriomyza trifolii in Japan. However, this endoparasitoid rarely emerges from L. trifolii pupae collected in the field. To determine why, we compared the parasitization, growth, and development of D. nipponica and the introduced parasitoid, D. sibirica, on L. trifolii hosts. When each parasitoid was only provided L. trifolii as a host, D. nipponica exhibited a slightly lower parasitization rate (confirmed by dissecting hosts, 34.7%) than D. sibirica (42.2%). However, the survival rate of parasitoid progeny within hosts was much lower for D. nipponica (7.2%) than for D. sibirica (69.4%), which was caused by the developmental arrest or death of D. nipponica at the prepupal stage within L. trifolii pupae. Furthermore, the survival rate of parasitoid progeny within hosts was much lower for D. nipponica (13.3%) than for D. sibirica (82.6%) when both parasitoids were allowed to parasitize artificially dwarfed individuals of Chromatomyia horticola, which is naturally much larger than L. trifolii and is a suitable host for both parasitoid species. The survival rate of progeny was lower for both D. nipponica and D. sibirica within smaller individuals of dwarfed C. horticola pupae. These results suggest that L. trifolii is large enough to host the growth and development of D. sibirica but too small for successful parasitization by D. nipponica.

No abstract