Effect by Contact and Ingestion of Essential Oils of Pennyroyal: Mentha pulegium L.(Lamiaceae) on Juvenile of Calliptamus barbrus (Orthoptera: Calliptaminae)

Abstract

This work is a study on the action of essential oils (EOs)of Pennyroyal Mentha pulegium against two larvaeL2 and L3 of Calliptamus barbarus (Orthoptera: Acrididae). The EOsare extracted by hydrodistillation protocol based on the use of a Clevenger. It should be noted that the yield of EOs obtained at the flowering stage (2.2%) is almost double that obtained at the foliage stage (1.2%).Gas Chromatography coupled to a mass spectrophometerGC-MS analysis revealed the presence of p-Menth-4 (8) -en-3-one, as the most frequently constituents of Mint, better known as Pulegone. We performed two ways of treatments: by contact and by alimentation (the duration of treatment is 3and 6 days respectively). By contact we have acquired a total mortality (100%) using the highest dose (48μl/ml) with a LD50 of 12.58 μl/ ml. In the opposite, by ingestion, the mortality rate obtained for the same dose was 80%while the LD50 was23.98 μl/ ml. Using the letal doses, the comparative effect of contact and ingestion between the essential oils show that the action by contact is stronger and faster to enter in the insect via the cuticulethan that byingestion. Finally authors concluded that the results were very satisfactory.