Biorational potential of Mentha essential oils of Indian origin: Comparative note on insecticidal efficacy, fumigant persistence, oviposition deterrence of Sitophilus oryzae

Natural compounds have widely gained their acceptance as biorationals for management of storing grain from insect pests. Mentha spp. are commercially important plant genus known for its distinct aroma. The present study is aimed towards the comparative insecticidal activity of four mint essential oils (Mentha arvensis, Mentha citrata, Mentha piperita and Mentha spicata) against rice weevil (Sitophilus oryzae). Further, the GC-MS analysis of mint essential oil's (EO's) exhibited diversity in aroma compounds, M. arvensis (menthol 61% and L-menthone 9.11%), M. citrata (linalool 36.74% and linalyl acetate 35.9%), M. piperita (menthol 36.28%, menthone 26.37% and isomenthone 5.15%) and M. spicata (54.14% of carvone and 20.97% of limonene). Whereas, the M. spicata EO exhibited the strongest toxicity (fumigant and contact) in both with and without food conditions around 100% mortality for 25 & mu;L dose within 24 h of exposure. The LC50 and LD50 values exhibited by M. spicata were 54.07 & mu;L/L and 11.5 & mu;L/100 cm2 respectively. Similarly, the concentrations of 2.5% and 5% of M. spicata EO also exhibited a strong fumigant and contact toxicity against S. oryzae within 24 h as compared to known prophylactic insecticide (0.3% of Deltamethrin). Besides, 100% oviposition deterrence exhibited by all the four mint EO's and 56% of AChE inhibition is noticed for M. spicata EO. Furthermore, post-treated grains showed no persistence of mint aroma residues and the treated grains retained the seed viability. Thus, on a comparative note, the M. spicata EO possess potential biorational traits for the effective management of stored grain from insect pests.

Automated summary

This study compared the insecticidal activity of four mint essential oils against rice weevil and found that M. spicata essential oil exhibited the strongest toxicity, causing 100% mortality. It also showed strong oviposition deterrence and AChE inhibition. The treated grains retained seed viability and showed no persistence of mint aroma residues.