Improving Parasitoid Performance by Improving Adult Food Quality : A Case Study for the Leafminer Parasitoid Hemiptarsenus varicornis (Hymenoptera : Eulophidae)

Leaf miners of the family Agromizydae contain many pest species that are often difficult to control exclusively with insecticides due to high levels of resistance. Biological control with insect parasitoids is an alternative or compatible option in leafminer management. Effective mass rearing systems of parasitoids are essential to successful biocontrol because cost of parasitoid production is often too high and lowering the cost is crucial to economically reasonable practices of biological control. Experiments were conducted to examine whether provision of protein sources as supplemental food could improve mass rearing efficiency of Hemiptarsenus varicornis, a parasitoid wasp attacking the leafminer Liriomyza trifolii. No significant difference was found in the number of ovipositions and host-feedings between female groups, i.e., females that had been fed on a honey solution and those fed on a honey-protein mixture. Females that fed on more hosts parasitized more hosts, suggesting that host-feeding was involved in an enhancement of egg production in H. varicornis. However, the relationships between the number of host-feedings and ovipositions did not differ between the female groups. These results indicated that provision of skim milk as a protein source did not improve parasitoid production. We discuss the importance of nutritional ecology and physiology of parasitoids for the fundamental understanding of parasitoid reproduction.