Résumé
OBJECTIVE@#To evaluate toxic activities of essential oils obtained from Rosmarinus officinalis and Lavandula stoechas against the fourth larval instars of Orgyia trigotephras.@*METHODS@#A total of 1 200 larvae were divided into three groups I II III. Group I was to investigate the effect of extracted essential oils from these aromatic plants as gastric disturbance. Bacillus thuringiensis and ethanol were used as control group. Group II was used as contact action and Group III was used as fumigant action. Decis and ethanol were used as control group. During the three experiments, the effect of essential oils on larvae was assessed.@*RESULTS@#The chemical composition of essential oils from two medicinal plants was determined and, their insecticidal effects on the fourth larval state of Orgyia trigotephras were assessed. The two simples presented an insecticidal activity, nevertheless Rosmarinus officinalis essential oil was less efficient compared to Lavandula stoechas one are discussed.@*CONCLUSIONS@#The relationship between the chemical composition and the biological activities is confirmed by the present findings. Therefore the potential uses of these essential oils as bioinsecticides can be considered as an alternative to the use of synthetic products.
Résumé
Objective: To evaluate toxic activities of essential oils obtained from Rosmarinus officinalis and Lavandula stoechas against the fourth larval instars of Orgyia trigotephras. Methods: A total of 1 200 larvae were divided into three groups I II III. Group I was to investigate the effect of extracted essential oils from these aromatic plants as gastric disturbance. Bacillus thuringiensis and ethanol were used as control group. Group II was used as contact action and Group III was used as fumigant action. Decis and ethanol were used as control group. During the three experiments, the effect of essential oils on larvae was assessed. Results: The chemical composition of essential oils from two medicinal plants was determined and, their insecticidal effects on the fourth larval state of Orgyia trigotephras were assessed. The two simples presented an insecticidal activity, nevertheless Rosmarinus officinalis essential oil was less efficient compared to Lavandula stoechas one are discussed. Conclusions: The relationship between the chemical composition and the biological activities is confirmed by the present findings. Therefore the potential uses of these essential oils as bioinsecticides can be considered as an alternative to the use of synthetic products.
Résumé
BACKGROUND: Essential oils extracted from aromatic and medicinal plants have many biological properties and are therefore an alternative to the use of synthetic products. The chemical composition of essential oils from two medicinal plants (Eucalyptus globulus and E. lehmannii) was determined and, their insecticidal effects on the third and fourth larval stages of Orgyia trigotephras were assessed. RESULTS: Larvae were collected from Jebel Abderrahmane (North-East of Tunisia), conserved in groups of 50/box (21 × 10 × 10 cm) at a temperature of 25°C. Larvae were tested for larvicidal activities of essential oils. Each oil was diluted in ethanol (96%) to prepare 3 test solutions (S1 = 0.05%, S2 = 0.10% and S3 = 0.50%). Essential oils were used for contact, ingestion and Olfactory actions and compared to reference products (Bacillus thuringiensis and Decis). Olfactory action of essential oils shows that larvae mortality is higher than contact action, lower than ingestion action. MTM and FTM of S3 of E. lehmannii were respectively 1 h 32 min and 1 h 39 min are higher than those of E. globulus (MTM = 51 min and FTM = 1 h 22 min 34 sec). Contact action of E. lehmannii oil shows low insecticidal activity compared to E. globulus. MTM are respectively (1 min 52 sec and 1 min 7 sec), FTM are (2 min 38 sec, 1 min 39 sec), are the shortest recorded for S3, on the third stage of larvae. The fourth stage of larvae, MTM are (2 min 20 sec and 2 min 9 sec), FTM are (3 min 25 sec, 3 min 19 sec). Ingestion action of essential oils is longer than the contact action, since the time of death exceeds 60 minutes for all species. CONCLUSION: Results shows that essential oils have a toxic action on nerves leading to a disruption of vital system of insects. High toxic properties make these plant-derived compounds suitable for incorporation in integrated pest management programs.