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Trichogramma wasps are tiny parasitoids of lepidopteran eggs, used extensively for biological control. They are often infected with the bacterial symbiont Wolbachia, which converts Trichogramma to an asexual mode of reproduction, whereby females develop from unfertilized eggs. However, this Wolbachia-induced parthenogenesis is not always complete, and previous studies have noted that infected females will produce occasional males. The conditions that reduce penetrance of the parthenogenesis phenotype are not well understood. We hypothesize that more ecologically relevant conditions of limited host access will sustain female-biased sex ratios. By restricting access to host eggs, we see a strong relationship between reproductive rate and sex ratio. We show that reproductive output in the first 24 hours is critical to the total sex ratio of the entire brood, and limiting oviposition in that period results in near-complete parthenogenesis that can be sustained for long periods, without any significant impact on total fecundity. Our data suggest that this phenomenon may be due to the depletion of Wolbachia when oviposition occurs relatively constantly, and that Wolbachia titers may recover when offspring production is limited. In addition to the potential to improve mass rearing of Trichogramma for biological control, findings from this study help elucidate the context dependent nature of a pervasive symbiotic relationship.