An investigation on the effect of ultraviolet rays and parasitoid wasp, Trichogramma brassicae in controlling the egg stage of potato tuber moth, Phthorimaea operculella

Phthorimaea operculella Zeller (Lep.: Gelechiidae), is one of the key pests of potato plants in fields and warehouses. This research was designed to determine interaction and the priority and delay of using two control factors including the parasitoid wasp, Trichogramma brassicae (Hym.: Trichogrammatidae) and UV-C radiation in controlling the egg stage of potato tuber moth (PTM), which has the least adverse effect on T. brassicae. The rate of oviposition and emergence of parasitoid on irradiated and control eggs was investigated. Also, ultraviolet rays were applied for 0, 8, 10, and 12 minutes on 1, 2, and 3-day-old eggs of PTM in two pre-parasitized conditions, and the second mode of irradiation was performed after parasitization, and the rate of parasitoid emergence was evaluated. The results showed that there was no significant difference between the two groups of eggs irradiated by UV-C rays and the control treatment. In UV-C irradiation on the parasitized PTM eggs, the percentage of parasitoid emergence decreased with the increase in the duration of irradiation, and in the case of irradiated-parasitized eggs, the rate of parasitoid emergence increased compared to the parasitized-irradiated eggs. The results of this study showed that 3-day-old eggs were more sensitive to ultraviolet rays than 1 and 2-day-old eggs. Also, the rate of emergence of parasitoid from irradiated-then-parasitized eggs increased compared to the parasitized-irradiated eggs. Therefore, in the simultaneous use of T. brassicae and UV-C radiation in controlling the egg stage of this pest and other target pests, first UV-C radiation and then release of T. brassicae is recommended.