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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
03/21/2017
Disease pressure Pathogen status
Fresno
(map)
Based on bud break, March 9, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
CARUTHERS-01.P, CAR 80 high reproduces every 5 days
Del_Rey/Fowler-01.P, DELF 50 intermediate reproduces every 15 days
EASTON-01.P, EAS 0 n/a no infection
KERMAN-01.P, KER 0 n/a no infection
KINGSBURG-01.P, KNG 80 high reproduces every 5 days
Kearney_Ag_Ctr-01.P, KAC 80 (S1) high reproduces every 5 days
SAND_RANCH-01.P, SR1 80 high reproduces every 5 days
Madera
(map)
Based on bud break, March 13, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
FIREBAUGH/ALISO-01.P, FRBA M    
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.
Collegeville-02.P, COL2 0 (S2) n/a no infection
LIVE_OAK-01.P, LIV 0 n/a no infection
LOCKEFORD-01.P, LOC 0 (S2) n/a no infection
LODI-01.P, LOD 0 n/a no infection

*   Bud break based on farm advisor countywide vineyard surveys:

  • Fresno: March 9 in Thompson Seedless
  • Madera: March 13 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 LIVE_OAK-01.P

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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