- Author: Stephen J. Vasquez
Consideration should be given to your Phomopsis management program with budbreak approaching. Valley growers should consider applying a fungicide to protect young succulent growth prior to spring showers. Phomopsis viticola pycnidia will begin producing spores that infect susceptible cultivars such as Thompson Seedless, Flame Seedless, Redglobe, Grenache and others. Timely fungicide applications are paramount to good Phomopsis management.
Springtime management
Registered fungicides applied from budbreak through 12” of growth (mid March-May) act as foliar protectants and need to be applied prior to rain events...
- Author: Stephen J. Vasquez
Grapevine powdery mildew is a pathogenic fungal disease of grapes, the management of which is a yearly challenge for California grape growers. Since the mid-80’s, multiple fungicides have been registered for grapevine powdery mildew management. The first of these was Bayleton, a demethylation inhibitor (DMI). It controlled mildew well for two seasons, after which growers noticed a sharp decrease in efficacy. Growers were experiencing powdery mildew fungicide resistance firsthand. Resistance to Bayleton prompted a survey which showed that mildew developed resistance to fungicides in many California vineyards. Since then, we have learned a lot about powdery mildew biology, fungicides, and resistance management.
