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.