| Summary: | The tea grey geometrid <i>Ectropis grisescens</i> has long been a significant insect pest of tea plants in China. Two parasitoids, <i>Parapanteles hyposidrae</i> and <i>Protapanteles immunis</i> (Hymenoptera: Braconidae: Microgastrinae), are the most important parasitoids in the larval stage of <i>E. grisescens</i>. Yet, the potential of these two parasitoids for controlling the tea grey geometrid is not known. Here, we studied the parasitism performance of these two parasitoid species on different host densities under different temperatures as well as the interference effect of parasitoid density. The results showed that both parasitoid species, <i>Pa. hyposidrae</i> and <i>Pr. immunis</i>, exhibited a Type II functional response towards the tea grey geometrid <i>E. grisescens</i> at four tested temperatures. With increasing the density of <i>E. grisescens</i> larvae, the number of parasitized larvae increased until a maximum was reached. The highest number of hosts parasitized by <i>Pa. hyposidrae</i> or <i>Pr. immunis</i> reached 14.5 or 14.75 hosts d<sup>−1</sup> at 22 °C, respectively. The estimated values of instantaneous searching efficiency (a) and handling time (h) for <i>Pa. hyposidrae</i> or <i>Pr. immunis</i> were 1.420 or 3.621 and 0.04 or 0.053 at 22 °C, respectively. <i>Pr. immunis</i> performed better than <i>Pa. hyposidrae</i> under higher temperatures. The parasitism rate by a single female parasitoid decreased with increasing parasitoid density at different temperatures, resulting in a reduction of searching efficiency. The findings of this study showed that <i>Pr.</i><i>immunis</i> could be a better effective biocontrol agent than <i>Pa. hyposidrae</i> against the tea grey geometrid.
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