Greenhouse research was conducted to evaluate the effects of POST-applied clopyralid and clopyralid plus additives (surfactants and herbicides) on eight processing spinach varieties for leaf injury and yield. Results demonstrate that when applied alone, clopyralid caused mild injury in the form of slight to moderate leaf malformations and crinkling in all tested spinach varieties. Leaf injury increased significantly 10, 20, and 35 days after treatment (DAT) when additives were mixed with clopyralid compared with when clopyralid was applied alone. Applications of clopyralid phenmedipham increased leaf injury over clopyralid applied alone and all other clopyralid additive treatments. Within varieties, spinach yields recorded 35 DAT were generally not reduced with any clopyralid additive treatment, except when phenmedipham was added to the mixture. The leaf injury associated with clopyralid in this study, though consistent across varieties, generally appears to be cosmetic and may not be detrimental to spinach yields or to the quality of spinach harvested for canning or freezing.
Nomenclature: Clethodim, clopyralid, phenmedipham, sethoxydim, s-metolachlor, spinach, Spinacia oleracea L. ‘DMC 66-09’, ‘DMC 66-07’, ‘DMC 66-16’, ‘F415’, ‘17047’, ‘Avon’, ‘157’, ‘Padre’