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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
04/18/2014
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 100 high reproduces every 5 days
Amador_Renwood-01.P, REN1, Renwood Winery 100 high reproduces every 5 days
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.
Lava_Cap-01.P, LAV1, Lava Cap 90 (E) high reproduces every 5 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 50 (E) intermediate reproduces every 15 days
Del_Rey/Fowler-01.P, DELF 20 (E) low is present
EASTON-01.P, EAS 50 (E) intermediate reproduces every 15 days
KERMAN-01.P, KER 100 (E) high reproduces every 5 days
KINGSBURG-01.P, KNG 20 (E) low is present
Kearney_Ag_Ctr-01.P, KAC 50 intermediate reproduces every 15 days
Laton_North-01.P, LATN 20 (E) low is present
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 20 low is present
Madera_North-01.P, MADN 20 (S1) low is present
Madera_South-01.P, MADS 90 (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 90 (S2) high reproduces every 5 days
LIVE_OAK-01.P, LIV 90 high reproduces every 5 days
LOCKEFORD-01.P, LOC 100 high reproduces every 5 days
LODI-01.P, LOD 100 high reproduces every 5 days
PETERS-01.P, PET 100 high reproduces every 5 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

S1 = missing data substituted with values from FIREBAUGH/ALISO-01.P
S2 = 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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