Issue link: http://read.dmtmag.com/i/333548
5 8 V I N E YA R D & W I N E RY M A N A G E M E N T | J u l y - A u g 2 014 w w w. v w m m e d i a . c o m BY TED RIEGER, SENIOR FEATURE EDITOR SENIOR FEATURE EDITOR Powdery Mildew Resistant vine breeding in progress Monitoring and Control Options Expand rape powdery mildew, caused by the fungal patho- gen Erysiphe necator, is a problem in vineyards worldwide, and is the most common fungal disease of grape vines in California. Powdery mildew (PM) can affect all vine green tissues, including stems, leaves and fruit, with characteristic symptoms of chlorotic tissue of the infected area and the pathogen's powdery, web-like growth. If left untreated, early fruit infections can result in berry stunt- ing, scarring and cracking, and increase bunch rot severity. Infection on leaves can result in leaf curl and chlorosis, which inhibit photosynthesis and fruit development and reduce berry sugar content. Research indicates that as little as 1%-5% dis- ease at harvest can cause "off" flavors in wine.