In French Guiana, the proliferation of certain insects, like termites and mosquitoes has a negative impact on human health and on the economy. But the wide use of synthetic insecticides is now being challenged due to their negative impact on the overall health of ecosystems and to the increased resistance of the insects targeted. The French National Center for Scientific Research (CNRS) and its partners are looking for a natural solution to these issues.
This innovative project has earned the CNRS in French Guiana the Air Liquide Foundation’s Award for scientific research on the environment.
An exceptional reservoir of biodiversity for research
The tropical rainforest covers nearly 90 % of the total surface area of this French overseas département, making it an ideal natural laboratory for studying environmental influences on the evolution of living organisms and their behavior. The CNRS is a member of the Mixed Ecological Research Unit of the Forests of French Guiana (EcoFoG), which has two aims: to understand the relationships between biodiversity and how forest ecosystems work, and to encourage innovation in value creation from forestry resources.
Chemical ecology as a source of inspiration
The CNRS’s project* aims at identifying natural molecules with insecticidal properties that are synthesized by plants and capable of being used as an alternative to synthetic molecules. It is urgent to find natural insecticides « which have advantages in terms of persistence and selectivity, with natural molecules being eliminated in the environment more quickly, first of all, as well as plants with a highly targeted chemical arsenal, » explains Emeline Houël, who is a CNRS research engineer working for EcoFoG and who is in charge of the project. First, plants in the forest that seem worthy of interest must be collected. Guillaume Odonne, a researcher at the CNRS in French Guiana, summarizes how this selection process is carried out: « By studying plants and the chemical mechanisms they use to protect themselves against insects or herbivores, we hope to find even more effective insecticidal molecules. It is these molecules that we intend to use to fight against other insects, especially those that transmit disease. »
The identification of insecticidal molecules in the laboratory
The different parts of the plant collected are dried and ground in the laboratory. The powder obtained is mixed with a solvent, which extracts the molecules. After evaporation, the crude extract obtained is tested on termites and mosquito larvae. « For the purposes of this project, we consider that plants have effective insecticidal properties if the larvae mortality rate exceeds 50% for a given dose of active insecticide extract (100 µg/ml), » explains Isabelle Dusfour, a medical entomologist at the Pasteur Institute of French Guiana, a partner of the CNRS.
Towards even more ecological research methods
The Foundation financed the acquisition of a rotary evaporator, which increases the efficiency of plant extract production, as well as a freeze-dryer, which makes it possible to test water-based extracts obtained from plants. The laboratory was also able to buy efficient systems for recovering evaporated solvents, limiting emissions and making it possible to reuse them in the laboratory. The project has already helped identify seven plants with insecticidal properties. A first patent on the larvicidal activity of a wood extract and its molecules has been filed and five publications are in the process of being finalized.
To find out more
* A study carried out with the support of the European Regional Development Fund and the Region of French Guiana, in partnership with the Pasteur Institute of French Guiana, the University of French Guiana, the University of the French Carribbean and Guyane Développement Innovation (GDI)