Pennyroyal Essential Oil as a Green Pesticide for Tribolium castaneum (Herbst) Management and its Effects on Substrate Quality and Acetylcholinesterase Inhibition

Abstract

Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is the most damaging beetle species destroying stored products. Their management are difficult because they are developing resistance to insecticide. Essential oil application as bio-pesticide is receiving renewed attention. Pennyroyal (Mentha pulegium L.) is a relevant crop in the production of EO. The insecticidal effect of Tunisian pennyroyal EO were investigated against T. castaneum adults on wheat flour substrate under different occupation space conditions after 30 and 60 days of storage. EO impacts on wheat flour quality, volatile compounds retained by the treated substrate and acetylcholinesterase (AChE) activity were examined. GC/MS analysis showed that EO major compounds was pulegone (39.15 %). Insect mortality was assessed when EO was applied at 196 µL/L air to the stored wheat flour at 50 % or 100 % container capacity. A highest mortality occurred at 50 % container capacity, with means at 32.8 % and 72.2 % after storing for 30 and 60 days, respectively. Volatile compounds retained by the treated wheat flour were characterized via Headspace analysis. Results underlined that long time of storage (mainly 60 days) allowed the retention of significant amounts of menthone. EO substrate treatment changed flour moisture and protein content. EO exhibited insecticidal activity via inhibiting acetylcholinesterase activity.