Chemical Composition and Insecticidal Activity against Tribolium Castaneum of Thapsia garganica L. Seed Essential Oil.

Due to the several side effects of synthetic pesticides, including environmental pollution, threats to human health, and the development of pest resistance to insecticides, the use of alternative healthy, available and efficient agents in pest management strategies is necessary. Recently, the use of essential oil obtained from aromatic plants has shown significant potential for insect pest management. For this reason, the essential oil isolated from seeds of Thapsia garganica L. was investigated for the first time for its chemical profile, and its toxicity and repellency effects against Tribolium castaneum adults. Qualitative and quantitative analyses of the chemical composition by gas chromatography coupled to mass spectrometry (GC/MS) revealed the presence of 18 organic volatiles representing 96.8 % of the total constituents. The main compounds were 1,4-dimethylazulene (51.3 %) followed by methyl palmitate (8.2 %), methyl linoleate (6.2 %) and costol (5.1 %). Concerning the repellent effect, results revealed that SEO (Seed Essential Oil) was very repellent towards T. castaneum adults, with 100 % repellency after 2 h of exposure. Furthermore, the essential oil exhibited remarkable contact toxicity against T. castaneum (93.3 % of mortality) at the concentration of 10 % (v/v). The median lethal dose (LD50 ) of the topical application of the seed essential oil was 4.4 %. These encouraging outcomes suggested that the essential oil from T. garganica seeds could be considered a potent natural alternative to residual persistent and toxic insecticides.

Chemical Composition and Insecticidal Activity of Crithmum Maritimum L. Essential Oil against Stored-Product Beetle Tribolium Castaneum.

Several plant essential oils have been used against diverse insect pests since, unlike conventional pesticides, they pose almost no risk to humans and the environment. For this reason, the essential oil (EO) isolated from the fresh leaves of Crithmum maritimum L. and its fractions (F1 -F5 ) obtained by chromatographic simplification were investigated for their chemical profile, as well as for their toxicity and repellency effects against Tribolium castaneum (Herbst) adults. The analysis by GC/MS allowed the identification of 92.8-99.1 % of the compositions of the total oil (EO) and of its fractions (F1 -F5 ). The EO and its fractions F3 -F5 were characterized by the presence of a high amount of phenylpropanoids (94.4, 94.8, 93.6, and 88.7 %, respectively): in all the samples, dill apiole was the most abundant component (EO: 94.1 %, F3 : 94.6 %, F4 : 93.4 %, and F5 : 83.3 %). In addition, the repellency assay results showed that the volatile fraction F5 and the complete EO exhibited a higher repellency towards T. castaneum (97 % and 93 %, respectively) after 2 h of exposure at the dose of 0.04 µL/cm2 . The median lethal dose of the topical application of the EO was 9 %. Furthermore, the fraction F1 possessed interesting contact toxicity against T. castaneum (80 % of mortality) at the concentration of 10 %. These results suggested that the essential oil of C. maritimum leaves might be used as an alternative to synthetic insecticides in order to prevent insects from damaging the stored products.

The life cycle of the root borer, Oryctes agamemnon, under laboratory conditions.

The root borer, Oryctes agamemnon Burmeister (Coleoptera: Scarabaeidae), has become a serious pest of date palm trees in southwest Tunisia. Under natural conditions, mated females lay eggs in different parts of palm tree: between the hairy roots, all along the stem at the leaf axils and at the base of cut branches. Larvae bore into targeted places of the plant and were never seen outside. Pupation takes place in the plant and emergence of the adults begins in June. Larval feeding causes extensive damage to the respiratory roots. To examine the life cycle more closely, the O. agamemnon life cycle was studied under laboratory conditions. Different larval stages were collected from infested oases in Tozeur and placed in plastic boxes with natural food that was collected from the oases. After emergence, adults were paired in opaque plastic boxes for mating with the same food substrate which also served as an oviposition site. Eggs were collected daily and isolated in new boxes. Hatched eggs were recorded. The number of larval instars was determined by measuring the width of cephalic capsules. Under laboratory conditions (23 +/- 2'C and 55 +/- 6% RH)embryogenesis took 14.3 +/- 1.42 days and the first, second and third larval instars were 33.1 +/- 2.69, 63.88 +/- 6.6 and 118.3 +/- 13.38 days respectively. The pupal period lasted 24.1 +/- 3.02 days and the adult 65.27 +/- 9.48 days. These facts indicated that O. agamemnon is univoltine.