Lethal and sublethal effects of Mentha longifolia free and nanoencapsulated essential oils on Anagasta kuehniella (Lep.: Pyralidae)

In previous study, nano hollow silica spheres have been synthesized by sol-gel method as a Mentha longifolia essential oil carrier and the success of essential oil encapsulation has been characterized based on particle size, polydispersity index, zeta potential, and encapsulation efficiency. The present research has been carried out on the findings of the previous study with the aim of evaluating 1) fumigant toxicity of Mentha longifolia free (M. EO) and nanoencapsulated (M. NP) essential oil against eggs, fifth instar larvae and adults of Anagasta kuehniella after 24, 48 and 72 h of exposure 2) topical toxicity of M. EO and M. NP against fifth instar larvae (mortality data obtained after 72 h exposure) 3) lifetime fecundity, %fertility, %adult emergence and copulation rate of A. kuehniella exposed to LC25 of M. EO and M. NP for 72 h. Fumigant toxicity was positively affected by the essential oil concentration and exposure time. Findings indicated that nanoencapsulation was associated with a 1.62-fold increase in the topical toxicity of M. longifolia essential oil to fifth instar larvae. Moreover, exposure to LC25 of M. EO and M. NP significantly decreased biological parameters (lifetime fecundity: 63 and 42 egg/female, percentage of fertility: 19.1 and 17.6%, percentage of adult emergence: 16.4 and 11.3%, copulation rate: 6.18 and 3.6% respectively). It is clear from the toxicological tests that nanoencapsulated essential oil produced stronger lethal and sublethal effects on A. kuehniella than free essential oil, thus can be regarded as potentially complementary or alternative to conventional insecticides in stored commodities.