Fumigant and persistence toxicity of eucalyptus, walnut and pennyroyal essential oil on Khapra beetle Trogoderma granarium (Evert.) (Coleoptera: Dermestidae)

Khapra beetle Trogodermagranarium (Evert.) (Coleoptera: Dermestidae), has been considered as one of the most invasive pest for stored products in the world. The insect has become tolerant to conventional pesticides including fumigant such as phosphine and methyl bromide. Application of plant essential oils can be a suitable alternative for fumigation. In this study, fumigant and persistence toxicity of the essential oils from leaves of Mentha pulegium L., Eucalyptus microtheca F. Muell and walnut hulls Juglans regia L. evaluated against T. granarium under laboratory conditions of 30±2ºC, 65±5% R.H and darkness. Adult stage have high sensitivity to essential oils. In a period of 48 h exposure, LC50 value against adult stage of T. granarium were 6028.66, 6383.48 and 5498.20 ppm for eucalyptus, walnut and pennyroyal essential oils, respectively. LC50 values indicated that essential oil of pennyroyal (confidence limit: 4646.17-6482.07) had the most insecticidal activity against T. granarium. There was significant differences among LC50 values at p<0.5. The persistence assay against adult stage of insect showed the LT50 value was 8.69, 9.71 and 8.54 d for eucalyptus, pennyroyal and walnut, respectively. Therefore, the persistence of pennyroyal (8.44-11.10) essential oil was the most among the tested plants.