Carfentrazone‐ethyl and glyphosate drift inhibits uredinial formation of Austropuccinia psidii on Eucalyptus grandis leaves

BACKGROUND The response to infection of Austropuccinia psidii in resistant (CLR‐383) and susceptible (CLR‐384) Eucalyptus grandis clones, exposed to herbicide drift of carfentrazone‐ethyl, glyphosate and a mixture of these two herbicides, was evaluated at microscopic and physiological levels. RESULTS Plants of the two clones showed symptoms of phytotoxicity caused by herbicide drift. However, net CO 2 assimilation rate, height and shoot dry matter were lower in CLR‐384 than in CLR‐383. At the ultrastructure level, the leaves of both clones exposed to the herbicides showed thylakoid disorganization and accumulation of starch grains in the chloroplasts. Only plants of CLR‐384 were infected by A. psidii , but when exposed to herbicide drift, rust severity was lower than in control plants. Six days after inoculation (dai), plants of this clone exposed to the herbicides had smaller uredinia than control plants. At 12 dai, non‐herbicide treated plants showed normal uredinia, containing abundant urediniospores. By contrast, plants exposed to the herbicides were less colonized by the fungus, and the uredinia were smaller with reduced production of urediniospores, which were sometimes not even detected. CONCLUSION Glyphosate and carfentrazone‐ethyl herbicide drift reduce infection and uredinial formation of A. psidii and to some extent induce basal resistance in a susceptible clone of E. grandis . © 2018 Society of Chemical Industry