The parasitoid Trichogramma brassicae Bezdenko is used for inundative releases in biological control programs against lepidopteran pests in agro-ecosystems. Study on the functional response of natural enemies is one of the necessary features for evaluating the efficiency of a natural enemies and selection of them for biological control programs. The objective of the present study was to determine the suitability of T. brassicae for controlling the Phthorimaea operculella (Zeller), a serious pest of stored potatoes in Iran. This is the first study to determine the functional response of T. brassicae to vary eggs densities of P. operculella. In this study, laboratory tests were conducted to determine the functional response of T. brassicae to different egg densities (1, 2, 4, 8, 16, 32, and 64) of its factitious host, the Mediterranean flour moth, Anagasta kuehniella Zeller and its natural host, the potato tuber moth, P. operculella at 26 ± 1 °C, 65 ± 5% RH, and 16: 8 h photoperiod. A type III functional response was observed on both host with a direct density dependent mortality up to sixteen host eggs and an inverse one upward. Results show that the searching efficiency was the same on both hosts but handling time was higher on P. Operculella eggs. The maximum rate of parasitism (T/Th) on A. kuehniella and P. operculella eggs were 25.29 and 21.10 host eggs per day respectively. This study has revealed the potential capacity of T. brassicae as an efficient biological control agent to suppress potato tuber moth.
