Lethal and deterrent efficacy of three plants extracts on the potato tuber moth, Phthorimaea operculella Zeller and influence on percent parasitism of Trichogramma brassicae

Phthorimaea operculella Zeller (PTM) is one of the most destructive pests of potato both in the field and store. The present study was conducted to assay lethal and deterrent activities of methanolic extracts of Maclura pomifera (Raf.) Schnied, Cotinus coggygria Scop and Valeriana officinalis L. on different growth stages of P. operculella. The most effective extract was also investigated on parasitism rate of Trichogramma brassicae Bezdenko. The experiments were carried out under laboratory conditions at 26 ± 1 °C, 65 ± 5 RH and a photoperiod of 8:16 (L:D). V. officinalis exhibited the highest efficacy against eggs and neonate larval penetration of potato tuber moth, which elicited LC50 values equivalent to 262.28 and 170.74 ppm, respectively. The most repellent extract against neonate larval penetration was V. officinalis followed by C. coggygria and M. pomifera (% repellency= 92.33, 90.66 and 83.33%, respectively). Oviposition preference trials after 24, 48 and 72 h demonstrated that the three methanolic extracts showed anti-ovipostional activity against PTM females and they preferred to oviposit their eggs on non-treated tubers. Additionally, there was no adverse effect of sub-lethal dose of V. officinalis on percent  parasitism of T. brassicae (66.66%).