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How the UC Davis Gubler-Thomas Powdery Mildew Model and McCrometer CONNECT HelpWine Growers Combat Grapevine Powdery Mildew

Posted on January 15, 2013


One of the most serious and persistent diseases that plague grape growers on the West Coast is Grapevine powdery mildew (Erisiphe necator). More dollars are spent on powdery mildew control than on any other grape pest, yet the disease still accounts for more crop losses than any other disease.

One of the most effective tools developed to date is the University of California Davis Gubler-Thomas Grape Powdery Mildew (GPM) model. Dr. Doug Gubler is an extension plant pathologist and lead author/developer of the Gubler-Thomas Grape Powdery Mildew Model. He has been working for more than 27 years helping grape growers combat grape powdery mildew.

Recovering control can be expensive with six significant effects on crop quality. Two examples are:

- Infection can shorten storage life of table grapes

- Wine quality can be affected by as few as three percent of diseased berries

The UC Davis Gubler-Thomas Grape Powdery Mildew (GPM) Model:

Dr. Gubler’s GPM model helps growers predict the onset of disease and sporulation by the pathogen growth conditions so that growers can proactively treat for the disease without wasting resources. The model uses weather conditions to track the primary infection and let growers know when to start treatment in the beginning of the season.

Dr. Gubler recently purchased 18 McCrometer CONNECT weather stations for use in ongoing research for disease risk management of grapevine powdery mildew. These wireless field stations have been used with the PMI model since it was introduced in 1995 in conjunction with automated weather networks in Napa, Sonoma, and Kern counties.

The same McCrometer CONNECT weather stations being used by Dr. Gubler and UC Davis are available for growers as well. Growers can use the Powdery Mildew model in a number of ways. The PMI index can be used as a general guideline or the grower can enter each treatment into the system’s web based software and track the detailed treatment recommendations provided by the model. This detailed use of the model allows the grower to integrate the exact control duration, wash off limits (if the treatment was counter-acted by being washed off), and an integrated spray stretching algorithm that allows growers to stretch the interval between treatments when weather conditions are not conducive for disease growth.

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