Abstract

GONZALEZ-CABRERA, Jaime; ARREDONDO-BERNAL, Hugo C.  and  STOUTHAMER, Richard. Quality assessment of Trichogramma parasitoids (Trichogramma spp.) from six mexican insectaries. Agrociencia [online]. 2014, vol.48, n.3, pp.321-329. ISSN 2521-9766.

Quality of mass-reared biological control agents is vital. There are reports that Trichogramma spp. failed to control the target pest, and poor quality may explain these failures. The first goal of this study was to determine which way of reproduction was practiced by Trichogramma spp. colonies from Mexican insectaries, either sexual or asexual, and the second goal was to determine whether those Trichogramma spp. colonies meet the quality standards suggested by the International Organization for Biological Control/ European Community (IOBC/EC). In March 2010, a letter was sent to 27 Trichogramma spp. producers. Six insectaries agreed to participate and sent dead samples of its colonies, a total of 10 colonies. For statistical analysis these colonies were grouped by species, either Trichogramma pretiosum or T. fuentesi. None of the Trichogramma spp. colonies were infected by parthenogenetic-inducing Wolbachia, i.e., all colonies reproduced sexually. Therefore, quality standards for sexual species were used: sex ratio (proportion females) ≥0.5, embryonic mortality ≤20 %, and total fecundity ≥40 eggs. Among the 10 Trichogramma spp. colonies there was great uniformity in sex ratio, embryonic mortality and total fecundity, i.e., per species there were not statistical differences among colonies. In sex ratio (0.552±0.038) and embryonic mortality (21± 4.48 %) the nine colonies of T. pretiosum barely fulfilled the minimum standards suggested by the IOBC/EC. Using hind tibia length as a proxy of total fecundity, the fecundity (37.85 eggs) of nine colonies of T. pretiosum and two colonies of T. fuentesi fell slightly below the standard suggested by the IOBC/EC. In México only sexual species of Trichogramma are mass-reared, but at low host densities asexual species (compared with sexual species) are more effective controlling the target pest. So, Mexican insectary personnel should also rear asexual species, and release one or the other depending of host density.

Keywords : Trichogramma pretiosum; Trichogramma fuentesi; quality control; mass rearing; PI-Wolbachia.

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