Comparative Efficacy of Trichogramma (Hymenoptera: Trichogrammatidae) Species and Strains for Biological Control of the Tomato Leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae): Laboratory-to-Field Assessments

Tuta absoluta (Meyrick), a new invasive pest in China, is a major threat to global tomato production. Trichogramma egg parasitoids are an effective approach to controlling this pest. In this study, we examined the potential of seven strains from four Trichogramma species, encompassing three native and commercially available representatives in China—namely, Trichogramma chilonis Ishii (strains TC-HN and TC-JL), T. dendrolimi Matsumura (TD-JL), and T. ostriniae Pang and Chen (TO-JL and TO-MY)—and one of South America origin—T. pretiosum Riley (TP-GS and TP-HN), a species commercially available for T. absoluta control but not evaluated in any previous studies in China. The host acceptance of the seven Trichogramma strains by T. absoluta was examined by placing parasitoid females with T. absoluta eggs on cardboard in tubes. The performance (life history traits and lifetable parameters) of four prospective strains, TC-HN, TC-JL, TO-JL, and TP-HN, was tested by using cardboard with T. absoluta eggs. The most promising strains, TC-HN, TC-JL, and TP-HN, were evaluated on a larger scale using cages in the laboratory to assess their parasitism capacity. The most promising strain, TC-JL (and TP-HN), was tested in field cages to assess its control efficiency under cropping conditions. The TC-JL and TC-HN strains of T. chilonis, the TO-JL strain of T. ostriniae, and the TP-HN strain of T. pretiosum showed greater host acceptance; the TP-HN strain of T. pretiosum showed a greater egg-card parasitism rate. Strain TC-JL outperformed other species/strains under laboratory conditions. In field cage tests, the larval population size and percentages of damaged plants and leaves in cages with TC-JL released were significantly reduced by 75.10%, 55.56%, and 64.69%, respectively, compared with those of the non-Trichogramma-release control. Our results indicate that the Asian native T. chilonis (particularly strain TC-JL), a dominant commercial biocontrol agent, should be included in IPM programs targeting T. absoluta in China. T. pretiosum (particularly strain TP-HN) could be a potential candidate for biocontrol of T. absoluta.