Exudation of Mesotrione from Potato Roots Injures Neighboring Plants

Mesotrione is an effective herbicide for volunteer potato control but is not selective in several crops, including onion and carrot. Studies were conducted in 2006 to evaluate the effectiveness of wiper-applied mesotrione for control of volunteer potato in a potato crop. Surprisingly, nontreated potatoes growing adjacent to mesotrione-treated plants exhibited bleaching symptoms resembling mesotrione injury. Additional field trials confirmed injury to nontreated plants growing within 26 cm of potatoes treated with mesotrione applied with a wiper at 0.25, 0.5, and 1% (v/v) solutions. Greenhouse bioassays confirmed that mesotrione applied to potato leaves moved down through the plant and was exuded into perlite potting medium in sufficient quantities to injure potato plants that were exposed to the leachate from the perlite pots. In tracer studies, 52% of C-labeled mesotrione applied to potato leaves was absorbed into the potato plant by 15 d and 15% of the absorbed C-mesotrione was exuded into the soil and soil leachate. Mesotrione applied to potato by the wick application method has potential to injure neighboring susceptible plants from root uptake of exuded mesotrione. Nomenclature: Mesotrione; carrot, Daucus carota L.; onion, Allium cepa L.; potato, Solanum tuberosum L.