Powdery Mildew - ID Photos - EL 34 Berries Softening

PIC: Powdery mildew is ever-present in a vineyard at low, even undetectable levels. Unfortunately in some cases it flares up causes bunch infection.  If it gets out of control it is almost impossible to bring down to minimal damage levels. (c) James Hook
A severe infection. (c) James Hook

Photos of Powdery mildew are from near the Range in the McLaren Vale GI – note how it has affected all of the ‘shot’ berries in the bunch. It shows you that disease was very active 4-6  weeks ago and powdery is very good at finding a way to infect fruit. This is in an otherwise well tended and healthy VSP vineyard with an open canopy.

The worst thing you can do if mildew pressure gets high and a serious infection becomes established is to use a fungicide to try to eradicate it.  All it does is build resistance to whatever class of fungicide you are using. When you take that approach, there are spores that are resistant and they will escape, and resistance will build. (c) James Hook