Other herbicides that are damaging include Dicamba, Glyphosate, Sulfonylurea, Imidazolinone and others. The most damaging time for herbicide drift is from budbreak to fruit set. Significant exposure to these herbicides can cause fruit deformation and potential crop loss, depending on the timing and intensity of the herbicide drift.

Sulfur products used for powdery mildew control can burn foliage when applied above 85°F. The temperature relationship is correlated with increases in the daily maximum, within a few days after application. Grapes in California can withstand sulfur applications (at lower rates) above 85°F if there is no major short-term changes in the daily maximum. Once vines are acclimated to higher temperatures the chance of burn is greatly reduced. Some grapes, such as labrusca types like ‘Concord’ and interspecific hybrids, are genetically sensitive to sulfur even at low temperatures.

Sulfur burn appears first as a bleaching between the veins. These turn brown, necrotic and dry out becoming brittle. Defoliation may occur. Injured fruit can develop brown to black scar tissue.

1. Talk to neighbors within a half mile radius of the vineyard and let them know the sensitivity of grapevines to herbicide drift. If possible, encourage them not to use the more volatile forms of 2,4-D. Be aware of potential drift from highway department sprays or those that may occur at parks or substations.
2. Use lower rates of sulfur when the daily maximum is expected to increase significantly within the next few days. Make applications during the cooler, early morning hours.