Control of grape powdery mildew with synthetic, biological, and organic fungicides: 2021 field trials

Akif Eskalen – UC Davis

This trial was conducted at the University of California Davis Plant Pathology Fieldhouse Facility from April to July 2021. Treatments were placed in a complete randomized block design. Spraying was completed on July 9th based on the berry brix level and treatments were evaluated for disease incidence and severity on July 20th 2021.
The trials consisted of soft chemistry products and synthetic fungicides. Spray frequencies varied from 7 day to 21-day intervals.

Powdery mildew is caused by the biotrophic fungus Erysiphe necator1; this polycyclic disease of grape causes losses to crop quality and yield and is considered one of the most economically important disease of grapes worldwide. This report details the findings of our annual powdery mildew fungicide trials on grapevine (Vitis vinifera, Cultivar Chenin Blanc – 10- yrs-old). Along with Chardonnay, Muscat blanc, Roussanne and Carignane, Chenin blanc is one of the highly susceptible wine varieties 2.

Magna-Bon CS 2005 Research Trial Results

Magna-Bon CS 2005 an OMRI-listed copper sulphate pentahydrate in-solution formula achieved outstanding results in the 2021 UC – Davis Grape Powdery Mildew Fungicide Efficacy Trials! Use less metallic copper than conventional coppers by using CS 2005! Combat Brown Rot, Downy Mildew, Phomopsis and Powdery Mildew in Grapes! Click here for application rates and instructions. 


As shown in Table 1 with an infection rate of 71%, CS 2005 had 83% control of Powdery Mildew!

In Table 2 with an infection rate of 46%, CS 2005 had 95% control of Powdery Mildew!

Application rates of Magna-Bon CS 2005 = 20oz per 100 gallons of water per acre, 14 day intervals


Click Here to Download the Powdery Mildew Research Trials Information Sheet. 

More proof that CS 2005 can help you in your vineyard…

JW Ray had issues with powdery mildew with his grapes at JOLO Winery, located in Mount Pilot, North Carolina. JOLO Winery is rated in the Top 7 wineries located outside of California according to Trip Advisor!

Here is JW’s message to Magna-Bon:

Frank, JW Ray here up in North Carolina. Just reporting that I’m in love with your product! I’ve sprayed it on three varieties (Vidal Blanc, Chambourcon, Traminette) known to have sensitivity to copper and they have performed spectacularly. I’ll be at 20 ounces of CS 2005 with 75 gallons of water per acre but it eradicated the early onset of powdery mildew!

Materials and Methods from Powdery Mildew Research Trials
A. Experimental design

  • Experimental design – Randomized complete block design with 4 replicates = 1 treatment
  • Experimental unit – 2 adjacent vines = 1 plot
  • Row and tree spacing – 11 ft (row) and 7 ft (vine) Plot unit area – 154 ft2
  • Area/treatment – 616 ft2 or 0.0141 acre/treatment (4 replicates = 1 treatment)
  • Volume water/Acre:
    – 50 gallons =0.71 gal/4 reps
    – 100 gallons (late April,) = 1.41 gal/4 reps
    – 150 gallons (late May) = 2.12 gal/4 reps
  • Equipment -Stihl SR 430 mist blower backpack sprayers

To read Akif Eskalen full report, click here!