Potentialité des huiles essentielles dans la lutte biologique contre la mouche blanche Bemisia tabaci Genn

Essential oils and their application in a food model

The aim of the study was to investigate the chemical composition, antioxidant, and antimicrobial activity of essential oils (Canarium luzonicum CLEO, Melaleuca leucadenron MLEO, Amyris balsamifera ABEO). There was Gas chromatographic-mass spectrometric analysis used for the characteristic of the semiquantitative composition of the essential oils. The DPPH method was used to determine the antioxidant activity. Minimum inhibitory concentrations (MIC) of essential oils against Stenotrophomonas maltophilia were analyzed in a 96-well plate. The broth microdilution method was used for the minimal inhibitory concentration. A gas-phase antimicrobial assay was used to determine inhibitory concentrations in a food model. CLEO proved to be the best with the lowest MIC 50 and 90 of 6.67 μL.mL-1 respectively 6.81 μL.mL-1 and antioxidant activity of 33.43% among the tested essential oils. The main volatile compounds CLEO were limonene 36.38%, elemol 16.65%, α-fellandren 12.18% and elemicin 9.59%. It showed inhibition of S. maltophilia growth in the food model at the lowest concentrations among the essential oils.

Mosquito Larvicidal Activity, Antimicrobial Activity, and Chemical Compositions of Essential Oils from Four Species of Myrtaceae from Central Vietnam

Mosquitoes are important vectors of several diseases, and control of these insects is imperative for human health. Insecticides have proven useful in controlling mosquito populations, but insecticide resistance and environmental concerns are increasing. Additionally, emerging and re-emerging microbial infections are problematic. Essential oils have been shown to be promising mosquito larvicidal agents as well as antimicrobial agents. In this work, the essential oils from four species of Myrtaceae (Baeckea frutescens, Callistemon citrinus, Melaleuca leucadendra, and Syzygium nervosum) growing wild in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The essential oils have been screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. Callistemon citrinus fruit essential oil, rich in α-pinene (35.1%), 1,8-cineole (32.4%), limonene (8.2%), and α-terpineol (5.8%) showed good larvicidal activity with 24-h LC₅₀ = 17.3 μg/mL against both Ae. aegypti and Cx. quinquefasciatus, and good antibacterial activity against E. faecalis (minimum inhibitory concentration (MIC) = 16 μg/mL) The 48-h larvicidal activities of M. leucadendra leaf essential oil, rich in α-eudesmol (17.6%), guaiol (10.9%), linalool (5.1%), (E)-caryophyllene (7.0%), and bulnesol (3.6%) were particularly notable, with LC₅₀ of 1.4 and 1.8 μg/mL on Ae. aegypti and Cx. quinquefasciatus. Similarly, M. leucadendra bark essential oil, with α-eudesmol (24.1%) and guaiol (11.3%), showed good antibacterial activity against. E. faecalis. Both B. frutescens and C. citrinus leaf essential oils demonstrated anti-Candida activities with MIC values of 16 μg/mL. The results of this investigation suggest that essential oils derived from the Myrtaceae may serve as "green" alternatives for the control of mosquitoes and/or complementary antimicrobial agents.

Susceptibility of MED-Q1 and MED-Q3 Biotypes of Bemisia tabaci (Hemiptera: Aleyrodidae) Populations to Essential and Seed Oils

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major pest of many agricultural and ornamental crops in tropical and subtropical regions causing damages that result in important economic losses. Insecticides are commonly used in greenhouses or fields to control B. tabaci populations leading to rapid evolution of resistance that render treatments inefficient. Therefore, and for environmental and human health concerns, other approaches must be developed for this pest management. In the present study, we compare, using the leaf dip method, the toxicity of three essential oils (Cymbopogon citratus, Ocimum americanum, and Hyptis spicigera) and three seed oils (Lannea microcarpa, Lannea acida, and Carapa procera) with three chemical insecticides (acetamiprid, deltamethrin, and chlorpyrifos-ethyl) on adults. Two B. tabaci biotypes (MED-Q1 and MED-Q3) belonging to the Mediterranean species and collected in Burkina Faso were used. Essential oils were analyzed by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector. We showed that these two biotypes have different levels of resistance to the three insecticides, MED-Q3 being more sensitive than MED-Q1. Moreover, they differ in the frequency of resistance alleles to insecticides, especially for organophosphates, as these alleles are almost fixed in MED-Q1. On the other hand, the two biotypes prove to be more susceptible to the plant extracts than to insecticides except for chlorpyrifos-ethyl, with essential oils that showed the highest insecticidal activities. Monoterpenes content were the most abundant and showed the highest insecticidal activities. Our results indicated that essential oils, but also seed oils, have the potential to constitute an alternative strategy of pest management.