A spray trial for powdery mildew control on winegrapes was conducted at Roederer Estate US in Philo in a block of conventionally farmed “Chardonnay” grapes. Nine treatments were used, including Rallye, MKP and Elexa, Elexa only, Erase and Rallye, Erase only, MKP only, AQ-10, and a water control. A randomized complete block design consisting of 4 replications of 3 vines was used. Materials were applied at 7-10 day intervals depending on powdery mildew pressure as indicated by an Adcon Weather Monitorinig Station. Experimental lots of wine were made for taste evaluation (six lots).
Unfortunately, powdery mildew failed to develop in the plot due to overall low pressure, and an effective prebloom micronized wettable sulfur spray program. In the coming year, the plot will be relocated to a higher pressure area, and prebloom sulfur sprays will not be applied to the test plot area.