Powdery Mildew Management Calculator for Grapevines

Your Approximate Location:

Or enter your city/town name and province/state [USA or Canada]:

incorrect format!
The date must be now or in the past!



Thank you! Your contribution helps keep this site up and running

Chart 1: Model developer and citation: R. L. Snyder, La Vine, P. D., Sall, M. A., Wrysinski, J. E., and Schick, F. J. Grape Mildew Control in the Central Valley of California Using the Powdery Mildew Index. U. C. Cooperative Extension Leaflet 21342 (April, 1983).
This model calculates risk based on temperatures of 20-35 C for more than six hours and integrates precipitation and extreme temperatures.
Chart 2: Model developer and citation: Thomas, C. S., Gubler, W. D., and Leavitt, G. 1994. Field testing of a powdery mildew disease forecast model on grapes in California. Phytopathology 84:1070 (abstr.). Weber E., Gubler, D., and Derr, A. Powdery mildew controlled with fewer fungicide applications. Practical Winery & Vineyard, January/February 1996.
This model considers leaf wetness, relative humidty as well as optimal growing conditions for the fungus.
University of California Integrated Pest Management:Powdery Mildew
Note: Future dates are predictions (for more accurate spraying times consult this calulator 5-7 days before your next planned spraying).
Temperatures are based on weather stations near you that are reliable, but predictions might be wrong, and your vineyard conditions may vary.
High humidity, low precipitation, cloudy skys, temperatures between 20-30C favor the fungus.

Note: Before using a model that was not field tested or validated for a specific location, a model should be tested for one or more seasons under local conditions to verify that it will work in the desired location.
Kumulus DF (wettable sulfur): Table grapes - Do not apply later than 1 day before harvest. Wine grapes - Do not apply later than 21 days before harvest.