Suitability of the Pest-plant System Tuta absoluta (Lepidoptera: Gelechiidae)-Tomato for Trichogramma (Hymenoptera: Trichogrammatidae) Parasitoids and Insights for Biological Control

The South American tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is a major pest that has recently invaded Afro-Eurasia. Biological control, especially by Trichogramma parasitoids, is considered to be very promising as a management tool for this pest. However further development of Trichogramma-based biocontrol strategies would require assessing the impact of released parasitoid offspring on the pest. Under laboratory conditions, we compared (i) the parasitism of five Trichogramma species-strains on the pest-plant system T. absoluta-tomato, and (ii) assessed various biological traits of parasitoids, previously mass-reared on a factitious host (Ephestia kuehniella), when developing on T. absoluta. In addition, we evaluated the overall efficiency of two specific Trichogramma species when released under greenhouse conditions in combination with a common natural enemy in tomato crop; the predator Macrolophus pygmaeus Rambur. Parasitoids emerging from T. absoluta on tomato showed lower parasitism rates and poor biological traits, e.g. wing deformations, reduced longevity, when compared to the control on the factitious host under laboratory conditions. Under greenhouse conditions, the parasitoids that developed on T. absoluta after initial releases were of low use for the biological control of T. absoluta. Parasitism tended to be lower when the predator was present. However, a slightly higher T. absoluta control level was achieved by combining the predator and the parasitoid T. achaeae. This study shows that Trichogramma parasitoids may not build up populations on the T. absoluta-tomato system, but that Trichogramma parasitoids can be used in combination with the predator to enhance biological control of the pest in tomato crops.