Damages from Monday’s frost event showed up a few days after. About 5-10% of shoots (or leaves) on our Merlot vines which is located near the bottom of a hill showed symptoms. Some are simply become necrotic, and others are showing mosaic symptoms.
Also, although there were drizzles here and there, rains from this weekend were not long enough to be disease events at our location. However, relative humidity was high (near 100%) throughout the last night. Such a condition can promote sporulation of downy mildew.