Efficacy of some chemical insecticides and plant extracts combined with Bacillus thuringiensis against Phthorimaea operculella

Phthorimaea operculella (Zeller, 1873) is one of the most damaging pests of potatoes in the world. Since the chemical pesticides play a key role in managing of potato tuber moth (PTM), the present study was conducted to assess the efficacy of Proteus®, Takumi®, Avaunt®, Dorsban®, Decis®, Consult® and Vertimec® against neonate larval penetration and one-day-old eggs of P. operculella. But adverse effects of chemical insecticides, actuated researchers to seek secure tools such as medicinal plants and biopesticides like Bacillus thuringiensis Berliner, 1715 for pest managements. Hence, we also examined toxicity of savory, ziziphora and cumin methanolic extracts against the pest under laboratory conditions. We also surveyed the synergistic/antagonistic interactions between the most effective insecticide and methanolic extract with Bt against PTM. Our results showed that both Vertimec® and savory synergized the performance of Bt against neonate larval penetration of P. operculella. Probit analysis of insecticides and methanolic extracts demonstrated that Vertimec® and Takumi® had high toxicities to the neonate larval penetration of PTM which exhibited LC50 values equivalent to 7.09 ppm and 0.008 g L−1, respectively. Savory was the most effective extract against larval penetration and hatching rate of the pest (LC50 = 440.36 and 635.93 ppm, respectively). Oviposition preference demonstrated that Vertimec® and Decis® exhibited inhibitory ovipositional effects against P. operculella.