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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 | Lake | 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
09/29/2018
Disease pressure Pathogen status
Amador
(map)
Based on bud break, April 7, in Zinfandel,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Amador_Eagle-01.P, EAG1, Screaming Eagle 30 (E) intermediate reproduces every 15 days
Amador_Renwood-01.P, REN1, Renwood Winery 30 (E) intermediate reproduces every 15 days
Calaveras
(map)
Based on bud break, April 7, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Ironstone-01.P, IRN1, Ironstone 30 (E) intermediate reproduces every 15 days
West_Point-01.P, WES1, West Point 0 (E) low is present
El Dorado
(map)
Based on bud break, April 7, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Fair_Play-01.P, FAI1, Fair Play 90 high reproduces every 5 days
Gold_Hill-01.P, GLD1, Gold Hill, Saureel Vineyards 0 low is present
Lava_Cap-02.P, LAV2, Lava Cap 70 (E) high reproduces every 5 days
Fresno
(map)
Based on bud break, March 16, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
CARUTHERS-01.P, CAR M    
Del_Rey/Fowler-01.P, DELF M    
EASTON-01.P, EAS M    
KERMAN-01.P, KER M    
KINGSBURG-01.P, KNG M    
Kearney_Ag_Ctr-01.P, KAC M    
SAND_RANCH-01.P, SR1 M    
Lake
(map)
Based on bud break, March 31, in ???,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
KELSEYVILLE-01.P, KEL 40 (E) intermediate reproduces every 15 days
MIDDLETOWN-01.P, MID 0 (E) low is present
Scotts_Valley-02.P, SVL 40 (S2) intermediate reproduces every 15 days
Upper_Lake-02.P, UPL 50 (E) intermediate reproduces every 15 days
Madera
(map)
Based on bud break, March 16, in Thompson Seedless,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
FIREBAUGH/ALISO-01.P, FRBA 30 (E) intermediate reproduces every 15 days
San Joaquin
(map)
Based on bud break, March 21, in Chardonnay,
you may need to adjust for other cultivars that emerge earlier than the indicated date.
Collegeville-02.P, COL2 50 (E) intermediate reproduces every 15 days
LIVE_OAK-01.P, LIV M    
LOCKEFORD-01.P, LOC 40 intermediate reproduces every 15 days
LODI-01.P, LOD 50 (S3) intermediate reproduces every 15 days

*   Bud break based on farm advisor countywide vineyard surveys:

  • Fresno: March 16 in Thompson Seedless
  • Lake: March 31 in ???
  • Madera: March 16 in Thompson Seedless
  • Amador: April 7 in Zinfandel
  • Calaveras: April 7 in Chardonnay
  • El Dorado: April 7 in Chardonnay
  • San Joaquin: March 21 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 KELSEYVILLE-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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