Grapevine Recovery from Herbicide Damage

Grapevines are notoriously susceptible to damage from herbicide drift, especially phenoxy herbicides such as 2,4-dichlorophenoxyaceticacid (2,4-D).  Two causes of injury occur: damage from particle contact with the leaves, shoots and/or flowers, and epinastic responses to volatilization of the herbicide that subsequently moves to the plants by diffuesive and air current movement. This report focusses on recovery from serious herbicide damage events of 2012 and 2013, with emphasis on differences related to genotype. We reported previously that these hericide incidents exhibited significantly different responses among several cultivars, with several genotypes being severely damaged, wheras there was less damage observed on a select small number of genotypes.  Observations after two and three years indicated varying recovery rates that were not always consistent with the earlier observations; that is, some genotypes that had severe symptoms recovered better than others that had appeared to be initially affected to a lesser degree.  Death of some plants (e.g., 'Chambourcin') may have been accelerated by the herbicide damage, or it may have been simply a matter of predictable winter-kill.  Conversely, a genotype exhibiting the most seevere herbicide damage following the 2012 incident ('Sabrevois') recovered better than predicted.  Questions regarding genotype susceptibility to herbicides as impacted by growing season and other environmentall factors will be presented for further discussion.