A systematic approach for finding herbicide synergies

Abstract

Combining herbicides into a double dose is a common approach to overcome the potential for herbicide resistance by weeds. Many herbicide mixtures can be antagonistic and they are rarely synergistic. Here, 24 commercial herbicides, each representing a mode of action were used to create a matrix of all 276 unique combinations to search for new synergies in agar with Arabidopsis thaliana. Herbicides were used at an appropriate sub-lethal dose such that any synergies gave visible growth inhibition. We found five synergies including three new ones, namely mesotrione-norflurazon, mesotrione-clethodim and paraquat-clomazone. All three new synergies were reproducible in soil-grown conditions. Interestingly, all three new combinations included a bleaching herbicide, suggesting synergy might be a class specific phenomenon. We also found that mesotrione-norflurazon and mesotrione-clethodim combinations remained synergistic against lettuce (Lactuca sativa), but not tef (Eragrostis tef). Our study shows that screening herbicide mixtures against A. thaliana is an efficient approach for finding rare herbicide synergies.

Herbicide mixtures: interactions and modeling

“…A recent study from the University of Western Australia described a systematic approach to investigate synergistic herbicide interactions and differentiate these from the more common additive or antagonistic relationships (Sukhoverkov, Mylne, 2021). Their study using 24 commercial herbicides were used to create a matrix of all 276 unique combinations to search for new synergies.…”

Can new herbicide discovery allow weed management to outpace resistance evolution?

“…Herbicide resistance research needs to systematically monitor the status of resistance to stand-alone herbicides and herbicide mixtures instead of relying on the assumptions that crossresistance for two herbicides would immediately extend to their combined action. Rare herbicide synergies between two active ingredients can be identified by a matrix of unique combinations 50 and then studies involving large collections of field populations can be conducted by screening ad hoc herbicide mixtures. 51 The goal is to better define the 'evolution in action' of cross-and multiple resistance patterns versus the validation of cost-effective herbicide solutions as mixtures of 'old' and new herbicides to be adopted within a diverse and integrated set of strategies for the long-term mitigation of weed resistance evolution.…”