UGA Extension Viticulture Blog

Widespread Powdery Mildew Resistance to QoI Fungicides in Georgia Vinifera Grapes

As the grape season wrapped up in 2018, county agents from Habersham, Lumpkin, Rabun, Towns and White Counties were busy collecting powdery mildew samples for a new multi-state USDA-SCRI grant, the “Fungicide Resistance Assessment, Mitigation and Extension Network for Wine, Table and Raisin Grapes,” also known as FRAME. This grant will study powdery mildew resistance to fungicides over the next four years — providing extensive and valuable information for grape producers in participating states.  See below for a list of the participating institutions in the FRAME Project Acknowledgement Slide.  We will soon be contacting grape producers to request your participation in some of these studies.  The initial survey results are also found below (2018 Georgia Powdery Mildew Resistance Map).  Each dot represents a vineyard in the participating counties, but specific vineyards are not indicated.  The bottom line is that powdery mildew is often resistant to the QoI fungicides.  We have also recently confirmed extensive resistance of the downy mildew pathogen to this same fungicide class.  As a result, it is doubtful that these fungicides will be of value for disease management in most Georgia vineyards.  We will be discussing fungicide and resistance-management options in detail at meetings this winter.  We look forward to working with our Georgia wine grape producers to develop better management programs as we move forward in 2019.

Powdery mildew in a northern Georgia vineyard (2018).

2018 Georgia Powdery Mildew Resistance Map

FRAME Project Acknowledgement Slide