Flavonoids as Insecticides in Crop Protection-A Review of Current Research and Future Prospects

Abstract

Pesticide overuse in agricultural systems has resulted in the development of pest resistance, the impoverishment of soil microbiota, water pollution, and several human health issues. Nonetheless, farmers still depend heavily on these agrochemicals for economically viable production, given the high frequency at which crops are affected by pests. Phytopathogenic insects are considered the most destructive pests on crops. Botanical pesticides have gained attention as potential biopesticides and complements to traditional pesticides, owing to their biodegradability and low toxicity. Plant-based extracts are abundant in a wide variety of bioactive compounds, such as flavonoids, a class of polyphenols that have been extensively studied for this purpose because of their involvement in plant defense responses. The present review offers a comprehensive review of current research on the potential of flavonoids as insecticides for crop protection, addressing the modes and possible mechanisms of action underlying their bioactivity. The structure-activity relationship is also discussed. It also addresses challenges associated with their application in pest and disease management and suggests alternatives to overcome these issues.

Keywords: biopesticides; flavonoids; insect control; mode of action.

Figure 1

Flavonoid chemical structure (phenyl rings are represented by the letters A and B, and the heterocyclic pyran ring by letter C).

Figure 2

General flavonoid biosynthesis pathway. Each block color represents a different flavonoid subclass. Legend: CHS, chalcone synthase; CHI, chalcone isomerase; FNS, flavone synthase; F3′H, flavanone 3′-hydroxylase; IFS, isoflavone synthase; HID, 2-hydroxyisoflavanone dehydratase; F3H, flavanone 3-hydroxylase; FLS, flavonol synthase; DFR, dihydroflavonol 4-reductase; LAR, leucoanthocyanidin reductase; ANS, anthocyanidin synthase; UFGT, UDP flavonoid glucosyl transferase.