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Agarwood, also known as Oud in perfumery, is a wood modified through contact with microorganisms. It emits a sweet and heady fragrance that is rare and precious. It derives its rarity from its very existence, from the trees of the genus Aquilaria. Indeed, agarwood arises from an interaction between the wood of those trees and associated microorganisms, which, after the trunk has been wounded, induce a reaction leading to the production of secondary compounds that give the wood its typical black coloration after oxidation. The compounds involved are mainly chromones and oxygenated sesquiterpenes, such as eudesmol, agarospirol, jinkoh-eremol and valerianol. Demand for agarwood on the international market has increased considerably over the last ten years or so. Its derivatives, including the essential oil extracted from it, are therefore expensive. Agarwood essential oil fetches US$ 5,000 to US$ 10,000 per kg, and is the most expensive oil on the market. That explains why this product is coveted by the owners of the trees, who attempt to compensate for its rarity by practising various agarwood induction methods. The methods, such as making holes or hammering nails into the trunks of the trees, or inoculating mixtures of biochemical products, are often harmful to the trees and detrimental to the composition of the essential oil extracted from them. Consequently, a consortium of farmers in French Guiana and scientists from CIRAD (French Agricultural Research Centre for International Development) is implementing the Aquil@Guyane project, designed to grow Aquilaria trees originating from Southeast Asia in French Guiana, with a view to producing agarwood with a controlled chemical composition that respects the biology and the ecology of the trees, while helping to conserve the genus Aquilaria, which is classed as being under threat of extinction (in CITES annex II) in its natural range. To that end, a biological induction trial was launched. Two induction methods were test

Aquilaria trees subjected to stress induce the formation of a transformed wood named agarwood. The formation of agarwood is a plant defense mechanism that occur in complex interactions with environmental microorganisms. Agarwood chemical compounds are mainly chromones and oxygenated sesquiterpenes such as eudesmol, agarospirol, jinkoh-eremol and valerianol, which are valued in perfumery. Its derivatives, notably the essential oil are therefore expensive. Agarwood essential oil costs 5,000 to 10,000 US $ per kg. Because of this important value and the scarcity of production from the wild, operators are planting Aquilaria and implementing various methods to induce agarwood. Many of these methods are deleterious for trees and even can alter the chemical composition of the essential oil. In this context, a consortium of farmers from French Guiana and scientists and from Centre de cooperation Internationale en Recherches Agronomiques pour le Développement (CIRAD) are developing the Aquil@Guyane project. This project aims at cultivating Aquilaria trees in French Guiana to produce agarwood of controlled chemical composition, respecting the biology and ecology of trees. In this frame we have tested the inoculation of trees with cubic and fibrous rot fungi to induce agarwood development in tree. Fungal strains used in this experiment have been isolated in the vicinity of Guianese Aquilaria plantations. Selected strains have been cultivated on wood test-sticks; infected sticks were then place in holes made with a drill in the trunks of Aquilaria. The yield of agarwood and chemical compositions of essential oils extracted from the so obtain blackened wood have been analyzed enabling to compare the different treatments. First, we evidence that the controlled inoculation of Aquilaria tree with selected fungal strains results in the production of agarwood and thus essential oils. The quality, in terms of composition of essential oils obtained among treatments was distributed betw

BACKGROUND: In tropical countries, netting is an effective sustainable tool for protecting horticultural crops against Lepi- doptera, although not against small pests such as Bemisia tabaci , while smaller mesh netting can be used in temperate regions. A solution is to combine a net with a repellent. Previously we identified repellent essential oils: lemongrass ( Cymbopogon citra- tus ), cinnamon ( Cinnamomum zeylanicum ), cumin ( Cuminum cyminum ) and citronella ( Cymbopogon winternarius ). The present study was designed to identify the active compounds of these essential oils, characterise their biological activity and examine theirpotentialforcoatingnets.Weinvestigatedtheefficiencyandtoxicityofnetsdippedindifferentsolutions.Wethenstudied the repellent effect with an olfactometer and the irritant effect by videotracking. RESULTS: Geraniol and citronellol were the most promising net coatings owing to their repellent effect. The repellency, irritancy or toxicity varied with the product and concentration, and these features were independent, indicating that the repellent and theirritant/toxicmechanismswerenotthesame.Thecombinedeffectsofthesedifferentcompoundsaccountforthebioactivity of the mixture, suggesting interactions between the compounds. CONCLUSION:Thisnewsustainablestrategyforprotectingvegetablecropsagainstwhitefliesisdiscussed,inadditiontotheuse of companion plants that could produce such bioactive compounds. (Résumé d'auteur

Background: Laboratory and field studies showed that repellent, irritant and toxic actions of common public health insecticides reduce human-vector contact and thereby interrupt disease transmission. One of the more effective strategies to reduce disease risk involves the use of long-lasting treated bednets. However, development of insecticide resistance in mosquito populations makes it imper ative to find alternatives to these insecticides. Our previous study identified four essential oils as alternatives to pyrethroids: Thymus vulgaris, Cymbopogon winterianus, Cuminum cyminum, Cinnamomum zeylanicum. The objectives of this study were to identify active compounds of these essential oils, to characterize their biological activity, and to examine their potential as a treatment for bednets. Methods: We evaluated the electrophysiological, behavioural (repellency, irritancy) and toxic effects of the major compounds of these oils against Anopheles gambiae strain 'Kisumu'. Results: Aldehydes elicited the strongest responses and monoterpenes the weakest responses in electroantennogram (EAG) trials. However, EAG responses did not correlate consistently with results of behavioral assays. In behavioral and toxicity studies, several of the single compounds did exhibit repellency, irritancy or toxicity in An. gambiae ; however, the activity of essential oils did not always correlate with ac tivity expected from the major components. On the contrary, the biological activity of essential oils appeared complex, su ggesting interactions between individual compounds and the insect under study. Data also indicated that the three effects appeared independent, suggesting that repellency mechanism(s) may differ from mechanisms of irritancy and toxicity. Conclusions: Based on the bioassays reported here, some of the compounds merit consideration as alternative bednet treatments.