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.