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How to Manage Pests

Interactive Tools and Models:
Grape Powdery Mildew Risk Assessment Index

The grape powdery mildew risk assessment index (RAI) is useful for determining disease pressure and how often you need to spray to protect the vines. For information on how to use the RAI, see the pest management guideline.

Powdery mildew risk for stations in counties:
| Fresno | Madera | San Joaquin |
Choose year

RAIs are based on actual weather data for stations that take appropriate readings.

County Active weather stations
(Click on station for year-to-date graph/daily data)
RAI*
for
09/29/2012
Disease pressure Pathogen status
Fresno
(map)
Based on bud break, March 19, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
CARUTHERS-01.P, CAR 0 low is present
Del_Rey/Fowler-01.P, DELF 0 low is present
EASTON-01.P, EAS 0 (E) low is present
KERMAN-01.P, KER 0 (E) low is present
KINGSBURG-01.P, KNG 0 (E) low is present
Kearney_Ag_Ctr-01.P, KAC 0 (S1) low is present
Laton_North-01.P, LATN 0 (S1) low is present
Madera
(map)
Based on bud break, March 19, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
FIREBAUGH/ALISO-01.P, FRBA 0 low is present
Madera_North-01.P, MADN 0 (E) low is present
Madera_South-01.P, MADS 0 (E) low is present
San Joaquin
(map)
Based on bud break, March 14, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
FARMINGTON-01.P, FGN M    
LIVE_OAK-01.P, LIV M    
LOCKEFORD-01.P, LOC M    
LODI-01.P, LOD M    
PETERS-01.P, PET M    

*   Bud break based on farm advisor countywide vineyard surveys:

  • Fresno: March 19 in Thompson Seedless
  • Madera: March 19 in Thompson Seedless
  • San Joaquin: March 14 in Chardonnay

M = missing data - no substitution values were available
P = missing data substituted with values from previous day
S1 = missing data substituted with values from CARUTHERS-01.P
S2 = missing data substituted with values from FARMINGTON-01.P
E = index was calcuated using previously substituted data

Because estimated data are included in the index, use reported RAI with caution. Interpret RAI using field surveys and your knowledge of the particular vineyard, along with additional weather data if you have it.

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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