Group 14 – PPO Inhibitor Resistance

The number of PPO resistance cases has tripled since 2012. Forty-six unique cases are described in the International Herbicide Weed Resistance Database (https://weedscience.org/Pages/MOA.aspx), with the first case reported in 2001 in Amaranthus tuberculatus. Currently, there are 42 cases reported in dicotyledonous weeds and 4 cases reported in monocotyledonous weeds. Many new unique cases of PPO resistance described since 2001 show resistance to additional herbicide MoAs (multiple-resistance). Among the 46 unique cases described so far, only 11 cases exhibit resistance to PPO inhibitors only, whilst 35 cases exhibit resistance to PPO inhibitors and at least one additional herbicide MoA.

The growing prevalence of multi-resistance, including resistance to PPO inhibitors, demands comprehensive weed control strategies that combine alternative modes of action with agrochemical innovation. The Group 14 – PPO Inhibitor Resistance Working Group is committed to delivering the latest insights on PPO resistance and sharing best practices to address this critical challenge.