Essential oils as biological alternatives to protect date palm (Phoenix dactylifera L.) against Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae)

The aims of this research were to determine the chemical composition of the essential oil of three Tunisian plants and to evaluate their biological activity against eggs, larvae, and adult insects of Ectomyelois ceratoniae Zeller. The essential oils extracted from leaves of Thymus capitatus (L.) Hoffmanns. & Link, Rosmarinus officinalis L. and needles of Pinus halepensis Mill. were analyzed by gas chromatography-mass spectrometry; 34, 16, and 56 constituents were identified, respectively. The major constituents were (Z)-caryophyllene (23.8%), beta-myrcene (20.5%) and alpha-pinene (13.3%) in P. halepensis oil, carvacrol (66.9%), p-cymene (9.1%), and delta-terpinene (6.2%) in T. capitatus oil and 1,8-cineole (47.5%), camphor (14.9%), alpha-pinene (14.1%), and borneol (13.1%) in R. officinalis oil. The insecticidal effects of essential oils on eggs, larvae, and adults of E. ceratoniae were investigated. Ovicidal activity of oils was studied by spray on eggs while larvicidal and adulticidal activities were assessed by fumigation and spray. Number of hatched eggs was verified after 10 d, larva and adult mortalities were observed after 6, 12, and 24 h. Globally, eggs and larvae were the most resistant to the three different oils, needing higher doses to obtain a higher mortality. The spray method was most effective than fumigation. Essential oil extracted from T. capitatus proved to be very toxic towards E. ceratoniae on all three phases at the dose of 20 mu L mL(-1) (100% inhibition), followed by the oil from R. officinalis (90-100% inhibition), nevertheless, weak activity was obtained with P. halepensis oil (68.3-85% inhibition). Results obtained may suggest that the essential oils of T. capitatus and R. officinalis possess high insecticidal activity and therefore, can be used in biotechnological application as natural preservative in stored dates and could be useful in managing populations of E. ceratoniae in field.