A Water Soluble ß-triketone Enriched Extract of Manuka Oil has Increased Efficacy Compared to Vinegar and D-Limonene in a Field and Greenhouse Evaluation

Authors: Barickman, Thomas - Casey Barickman; Cantrell, Charles; Reichley, Amber

Submitted to: ACS Agricultural Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2024
Publication Date: N/A
Citation: N/A
DOI: https://doi.org/10.1021/acsagscitech.4c00225

Interpretive Summary: 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 bioherbicides has become increasingly urgent in modern agriculture as the approved specialty and organic crop bioherbicides have nonspecific modes of action with no systemic activity. Introducing new bioherbicides, that are safe, effective, and have a more specific plant target, is essential to diversify weed control strategies. By fostering innovation in bioherbicide development we can safeguard our specialty and organic cropping 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. The current study is experimenting with Manuka oil, which is derived from the leaves and branches of the Manuka tree that is native to New Zealand. Previous research on Manuka essential oil has shown that it is safe for personal use as a treatment for skin irritation, thus showcasing the safety of the extracted oil. However, the discovery of the components in Manuka oil have shown promise as an agricultural bioherbicide. Manuka oil contains a family of chemicals called triketones that have a plant specific target that significantly reduces the plants ability to photosynthesize and ultimately killing the plant. In the current study, we tested a 2% and 4% solution of the triketones against other organically approved bioherbicides and the weed killer, Roundup against three weed species that are common in agricultural field, residential landscapes, and the common garden. The 4% solution of the triketones was very effective against the three weed species and had better results compared to the organic bioherbicides. Additionally, the 4% solution of the triketones was just as effective in controlling the three weed species as the Roundup herbicide treatment. Overall, the results show that the Manuka oil extracted triketone solution was effective in reducing the growth of the three weed species and in turn has potential in being developed as a new bioherbicide for commercial agricultural and residential applications.

Technical Abstract: 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 diversify weed control strategies, minimize the risk of resistance development, and ensure 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 ß-triketones. The ß-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 ß-triketone extract at 2% and 4% had up to 97% control against different weed species in field and greenhouse evaluations. The ß-triketone extract was significantly more efficacious verse other bioherbicides such as the 20% vinegar and 12.5% D-limonene. Additionally, the ß-triketone extract was just as effective as the 2% glyphosate treatment in the greenhouse evaluation against Amaranthus palmeri and Digitaria sanguinalis. The ß-triketone extract also reduced Cyperus esculentus growth by 70% at 9 days after treatment. Thus, there is significant evidence that commercializing a water soluble ß-triketones 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 of bioherbicides is critically imperative.