Grape Powdery Mildew Control in California Vineyards [2026]

OVERVIEW

Grape Powdery Mildew is the number one disease in California vineyards. More dollars are spent on powdery mildew control and, yet, this disease still accounts for more crop losses than any other grape pest. This course, sponsored by BASF, explores the different fungicide classes; treatment options for powdery mildew in California; resistance management, and regional differences in disease development. It also includes a detailed approach to using the UC Powdery Mildew Risk Assessment Index (RAI) to predict infections. Seasonal patterns of disease development differ from region to region (as well as year to year), and cost-effective management strategies must be based on local conditions that favor or inhibit pathogen reproduction. Season-long control depends on reducing early-season inoculum and subsequent infections with well-timed fungicide applications. Spray timing and frequency (and coverage) is everything; these vary depending on local weather, temperature, varietal susceptibility, vine growth stage and material choice.

Course Features

Lectures 14
Questions 20
Duration 1.5 h (approx)

COURSE OUTLINE
- Introduction
  
  7 min.
- General Disease Epidemiology
  
  13 min.
- Powdery Mildew (Erysiphe necator) Symptoms
  
  5 min.
- Treatment
  
  2 min.
- Critical Role of Temperature and Moisture
  
  6 min.
- Variety Susceptibility
  
  1 min.
- Regional Differences in Disease Development
  
  5 min.
- Monitoring for Powdery Mildew
  
  3 min.
- To Trigger the RAI
  
  3 min.
- Weather Stations
  
  5 min.
- General Management Guidelines
  
  4 min.
- Pre-Bloom Control Strategies
  
  3 min.
- Cautions with Sulfur and Oil
  
  4 min.
- Resistance Management 101 and Fungicide Resistance
  
  10 min.

CREDIT INFORMATION

This course is accredited by:

California Department of Pesticide Regulation (1 hour Other)
Certified Crop Adviser (CCA) Accredited in U.S. and Canada (2 hours IPM)
Hawaii Department of Agriculture (1 CEU, Private 1, Commercial 1a, 10)
Oregon Department of Agriculture (1 Credit, Core)
Pennsylvania Department of Agriculture (2 credits each: 00, PC, 02, 18)
Tennessee Department of Agriculture (1 Hour in C01, C03, C10, C12)
Washington State Department of Agriculture (Credit: Max: 1)
West Virginia Department of Agriculture (2 Credits in Categories 1, 11, 12, and private applicator)