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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 | Amador | El Dorado | 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
09/29/2014
Disease pressure Pathogen status
Amador
(map)
Based on bud break, March 24, in Zinfandel,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Amador_Eagle-01.P, EAG1, Screaming Eagle 20 (S1) n/a no infection
Amador_Renwood-01.P, REN1, Renwood Winery 20 (E) n/a no infection
El Dorado
(map)
Based on bud break, March 14, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Fair_Play-01.P, FAI1, Fair Play 50 (E) intermediate reproduces every 15 days
Lava_Cap-01.P, LAV1, Lava Cap M    
Lava_Cap-02.P, LAV2, Lava Cap 50 (E) intermediate reproduces every 15 days
Fresno
(map)
Based on bud break, March 7, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
CARUTHERS-01.P, CAR 100 (E) high reproduces every 5 days
Del_Rey/Fowler-01.P, DELF 100 (E) high reproduces every 5 days
EASTON-01.P, EAS 100 (E) high reproduces every 5 days
KERMAN-01.P, KER 100 (E) high reproduces every 5 days
KINGSBURG-01.P, KNG 100 (E) high reproduces every 5 days
Kearney_Ag_Ctr-01.P, KAC 100 (E) high reproduces every 5 days
Laton_North-01.P, LATN 50 (E) intermediate reproduces every 15 days
Madera
(map)
Based on bud break, March 7, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
FIREBAUGH/ALISO-01.P, FRBA 100 (E) high reproduces every 5 days
Madera_North-01.P, MADN 100 (E) high reproduces every 5 days
Madera_South-01.P, MADS 100 (E) high reproduces every 5 days
San Joaquin
(map)
Based on bud break, March 11, 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 50 intermediate reproduces every 15 days
LOCKEFORD-01.P, LOC 50 (E) intermediate reproduces every 15 days
LODI-01.P, LOD 50 intermediate reproduces every 15 days
PETERS-01.P, PET 30 intermediate reproduces every 15 days

*   Bud break based on farm advisor countywide vineyard surveys:

  • Fresno: March 7 in Thompson Seedless
  • Madera: March 7 in Thompson Seedless
  • Amador: March 24 in Zinfandel
  • El Dorado: March 14 in Chardonnay
  • San Joaquin: March 11 in Chardonnay

M = missing data - no substitution values were available
S1 = missing data substituted with values from Amador_Renwood-01.P
S2 = missing data substituted with values from Lava_Cap-02.P
S3 = missing data substituted with values from LIVE_OAK-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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