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. RAIs are based on actual weather data for stations that take appropriate readings.
| County | Active Weather stations | RAI* for 09-29-2015 |
Disease pressure | Pathogen status |
Amador
Based on bud break, March 26, in Zinfandel, may need to adjust for other cultivars that emerge earlier than the indicated date. |
|---|---|---|---|---|
| Amador Rendwood | 0 ( P ) | low | present | |
| Amador Screaming Eagle | 20 ( P ) | low | present |
Calaveras
Based on bud break, March 20, in Chardonnay, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Ironstone (IST) | 40 ( P ) | moderate | reproduces every 15 days |
El Dorado
Based on bud break, March 9, in Chardonnay, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Fair Play | 100 ( P ) | high | reproduces every 5 days | |
| Lava Cap (LAV) | 20 ( P ) | low | present |
Fresno
Based on bud break, March 6, in Thompson Seedless, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Caruthers | 20 ( P ) | low | present | |
| Del Rey | 20 ( S1 ) | low | present | |
| Easton | 20 ( P ) | low | present | |
| Kearney Ag Center | 0 ( P ) | low | present | |
| Kerman | 40 ( P ) | moderate | reproduces every 15 days | |
| Kingsburg | 0 ( P ) | low | present | |
| Sand Ranch | 20 ( P ) | low | present |
Madera
Based on bud break, March 6, in Thompson Seedless, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Firebaugh | 80 ( P ) | high | reproduces every 5 days |
San Joaquin
Based on bud break, February 28, in Chardonnay, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Collegeville (COL) | 20 ( P ) | low | present | |
| Lockeford (LOC) | 20 ( P ) | low | present | |
| Lodi (LangeTwins) | 0 ( P ) | low | present |
Sutter
Based on bud break, February 28, in Chardonnay, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Live Oak (LIV) | 0 ( P ) | low | present |
P =
missing data substituted with values from previous day
S1 = missing data substituted with values from Kearney Ag Center
Because estimated data is 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.