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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 | Calaveras | 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
05/27/2015
Disease pressure Pathogen status
Amador
(map)
Based on bud break, March 26, in Zinfandel,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Amador_Eagle-01.P, EAG1, Screaming Eagle 60 (E) high reproduces every 5 days
Amador_Renwood-01.P, REN1, Renwood Winery 60 (E) high reproduces every 5 days
Calaveras
(map)
Based on bud break, March 20, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Ironstone-01.P, IRN1, Ironstone 60 (E) high reproduces every 5 days
El Dorado
(map)
Based on bud break, March 9, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Fair_Play-01.P, FAI1, Fair Play 60 (E) high reproduces every 5 days
Lava_Cap-02.P, LAV2, Lava Cap 60 (E) high reproduces every 5 days
Fresno
(map)
Based on bud break, March 6, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
CARUTHERS-01.P, CAR 0 (E) n/a no infection
Del_Rey/Fowler-01.P, DELF 0 (E) n/a no infection
EASTON-01.P, EAS 0 (E) n/a no infection
KERMAN-01.P, KER 0 (E) n/a no infection
KINGSBURG-01.P, KNG 0 (E) n/a no infection
Kearney_Ag_Ctr-01.P, KAC 0 (E) n/a no infection
Laton_North-01.P, LATN 0 (S1) n/a no infection
SAND_RANCH-01.P, SR1 0 (E) n/a no infection
Madera
(map)
Based on bud break, March 6, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
FIREBAUGH/ALISO-01.P, FRBA 40 (E) n/a no infection
Madera_North-01.P, MADN 40 (S2) n/a no infection
San Joaquin
(map)
Based on bud break, February 28, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Collegeville-02.P, COL2 100 (E) high reproduces every 5 days
LIVE_OAK-01.P, LIV 100 (S3) high reproduces every 5 days
LOCKEFORD-01.P, LOC 100 (E) high reproduces every 5 days
LODI-01.P, LOD 100 (P) high reproduces every 5 days
PETERS-01.P, PET 100 (P) high reproduces every 5 days

*   Bud break based on farm advisor countywide vineyard surveys:

  • Fresno: March 6 in Thompson Seedless
  • Madera: March 6 in Thompson Seedless
  • Amador: March 26 in Zinfandel
  • Calaveras: March 20 in Chardonnay
  • El Dorado: March 9 in Chardonnay
  • San Joaquin: February 28 in Chardonnay

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 FIREBAUGH/ALISO-01.P
S3 = missing data substituted with values from LOCKEFORD-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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