Quality assessment of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) in eggs of Sitotroga cerealella (Lepidoptera: Gelechiidae)

Abstract

The establishment and maintenance of egg parasitoids in laboratory may be related to the type of alternative host and the number of successive generations. Through this work we studied the change in biological traits of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) reared for 22 generations in eggs of Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae). This parasitoid species was collected from tomato fields, in Ibitirama municipal district, state of Espírito Santo, Brazil, that are 380 m above sea level. The parasitism rate of T. pretiosum ranged from 36.25 ± 3.32% to 67.75 ± 2.57% with lower values in the generations F₀, F₃, F₅ and F₂₁. The highest parasitism rate took place in generation F₇. The viability of T. pretiosum ranged from 89.31 ± 8.75% to 100.00 ± 0.00% showing the smallest value in generation F₁₂. Adult longevity and biological cycle of T. pretiosum showed decreasing trend because of an increase of generations in laboratory. The sexual ratio of T. pretiosum was not significantly affected, ranging from 0.3 ± 0.11% to 0.8 ± 0.09, during the experiment.