Botanicals a sustainable strategy for crop protection?

The Laboratory of Chemistry of Natural Molecules (LCMN) has long been dedicated to the extraction, characterization, and utilization of plant secondary metabolites for applications in agronomy, with a special focus on essential oils. Plant extracts or pure compounds extracted from plants are known as botanicals and are indeed being increasingly employed in various sectors. Among these, their valorization as biopesticides in agronomy addresses a wide spectrum of applications including herbicidal, fungicidal, insecticidal, bactericidal, virucidal, and nematicidal purposes. Numerous compounds, either isolated or derived from more complex plant extracts, contribute to the formulation of these botanicals which offer several advantages, such as a generally low toxicity to users and consumers, a minimal ecotoxicity, and a good biodegradability. However, while their activity can sometimes rival that of conventional biocides originating from synthetic chemistry, this is not always the case.

In this presentation, we will outline the advantages and disadvantages of these botanicals and engage in a discussion on their sustainability. Many questions could indeed be raised about their use, such as:

- Should agricultural land be utilized to grow plants for protecting other plants?

- Is it necessary to excessively harvest naturally growing plants to produce essential oil for a use in the formulation of biopesticides?

- Should wood or other fossil energy sources be used in tropical regions to distill plants in order to produce essential oils which will be used for the protection of cultivated plants in temperate environments?

In addressing these considerations, the LCMN explores various approaches.

- The use of by-products such as bark or the use of invasive tropical plants as starting plant material. - The direct use of whole plant parts rather than the use of essential oils.

- The co-cultivation of essential oil plants in horticultural plots, protecting consumable plants from insect pests and subsequently producing essential oil for additional income.

- The study of the variability in the composition and therefore the biological activities of essential oils.

- The study of induced allelopathy traits where plants produce their own metabolites reducing weed germination and growth.

- The use of in vitro culture to produce targeted secondary metabolites.

The use of plants to protect other plants through the valorization of "botanicals" is a fascinating subject that draws on various disciplines, with potential applications both in North and South countries. However, a substantial journey lies ahead to gain an in-depth understanding of the mechanisms at play and develop sustainable valorization strategies to replace conventional pesticides with bio-based solutions.