A Water-Soluble β-Triketone Enriched Extract of Manuka Oil Has Increased Weed Control Efficacy Compared to Vinegar and D-Limonene in a Field and Greenhouse Evaluation

Weed management strategies for specialty and organic crop production are challenging due to limited chemical weed control products with good efficacy that are cost-effective. The need for new bioherbicide modes of action has become increasingly urgent in modern agriculture, as most bioherbicides have nonspecific modes of action with no systemic activity. Introducing new modes of action is essential to diversifying weed control strategies, minimizing the risk of resistance development, and ensuring sustainable weed management practices. By fostering innovation in bioherbicide development and promoting the use of novel modes of action, we can safeguard our agricultural systems, reduce the environmental impact of weed management, and maintain the ability to feed a growing global population while preserving the long-term health of our ecosystems. Manuka oil is derived from the leaves and branches of the Manuka tree (Leptospermum scoparium) and contains β-triketones. The β-triketone-rich fraction contains leptospermone and inhibits a key enzyme, p-hydroxyphenylpyruvate dioxygenase (HPPD). This process directly inhibits carotenoid biosynthesis, upstream in the biochemical pathway, which causes damage to the photosynthetic apparatus and leads to bleaching of the leaf tissue, which eventually kills the plant. The β-triketone extract at 2% and 4% had up to 97% control against different weed species in field and greenhouse evaluations. The β-triketone extract was significantly more efficacious vs other bioherbicides such as 20% vinegar and 12.5% D-limonene. Additionally, the β-triketone extract was just as effective as a 2% glyphosate treatment in the greenhouse evaluation against Amaranthus palmeri and Digitaria sanguinalis. The β-triketone extract also reduced Cyperus esculentus growth by 70% at 9 days after treatment. Thus, there is significant evidence that commercializing a water-soluble β-triketone-enriched extract of Manuka oil can be an effective weed control strategy in crop production systems, especially in specialty and organic cropping systems where the need for bioherbicides is critically imperative.