Chemical profiling and bioactivities of essential oils from Thymus capitatus and Origanum compactum against Tribolium castaneum

The use of essential oils has emerged as an ecofriendly solution for controlling different pests, particularly insects of stored products. Essential oils (EOs) from Thymus capitatus (TC) and Origanum compactum (OC) have received less attention for these bioactivities. Therefore, our study aimed to assess the repellent, antifeedant and contact toxicity of their EOs against a major stored product pest Tribolium castaneum. Besides, GC -MS was also carried out to determine the compounds responsible for the observed bioactivities. Regarding contact toxicity, LC50 values were 0.58 and 0.35 mu L/cm2 for TC and OC after 24 h of exposure, respectively. For the repellent effect, the percentage of repellency (PR) was variable across different concentrations and exposure durations. TC exhibited the best PR (98%) after 3 h of exposure at 0.031 mu L/cm2. For prolonged repulsive effect (24 h), TC sustained its repulsive efficacy with a PR of 90% at 0.062 mu L/ cm2 followed by OC with a PR of 88% at 0.125 mu L/cm2. As for the antifeedant effect, both EOs had a significant impact on nutritional indexes, especially the feeding deterrent index and relative consumption rate. OC displayed a notable effect, causing 59% of feeding deterrence at 1.92 mu L/ pellet. These multifaced effects can be explained by the high content of carvacrol in both EOs (OC: 90% and TC: 78%). These multifaced effects demonstrated through different exposure routes and bioassays promote the use of T. capitatus and O. compactum EOs as a sustainable management strategy to control T. castaneum.