Abstract:Ocinara varians Walker is one of the most serious insect pests of ornamental plants in southern China in recent years. In order to screen effective Trichogramma species against O.varians, the parasitic capacity and suitability of three egg parasitoids, Trichogramma pretiosum Riley, T.dendrolimi Matsumura and T.euproctidis (Girault), to different ages of O.varians eggs were compared in the laboratory. The results revealed that the number of eggs parasitized by T.dendrolimi and T.euproctidis decreased as the host egg age increased, and the two species reached their maximum parasitizing capability on 6 h-host egg with 15.9 and 12.2 eggs per female, respectively. However, the number of eggs parasitized by T.pretiosum increased firstly and then decreased, and its maximum parasitizing capability was observed on 24 h-host egg with 8.3 eggs per female. The parasitizing capability of T.dendrolimi was higher on all host egg ages than the other two species of Trichogramma. When the host egg age was over 72 h, the parasitizing capabilities of three species declined dramatically. The emergence rates of three Trichogramma species reached the highest on 6 h-parasitized eggs, and dramatically decreased when the age of parasitized eggs were over 72 h. T.dendrolimi and T.euproctidis had the strongest fatalities to 6 h-host eggs, while T.preti- osum had the strongest fatalities to 24 h-host eggs. In conclusion, T.dendrolimi showed the best parasiti- zing capability and suitability on O.varians eggs, indicating that it had the potential ability as an effective biological control agent for controlling O.varians.