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 11-30-2024 |
Disease pressure | Pathogen status |
Amador
Based on bud break, April 17, in Zinfandel, may need to adjust for other cultivars that emerge earlier than the indicated date. |
|---|---|---|---|---|
| Amador Screaming Eagle | 0 | low | present | |
| Rombauer Sierra Foothills | 0 | low | present |
Calaveras
Based on bud break, April 17, in Cabernet Franc, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Ironstone (IST) | 0 | low | present | |
| West Point | 0 | low | present |
El Dorado
Based on bud break, March 28, in Sangiovese, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Fair Play | 0 | low | present | |
| Gold Hill (SRL) | 0 | low | present | |
| Lava Cap (LAV) | 0 | low | present |
Fresno
Based on bud break, March 11, in Thompson Seedless, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Caruthers | 0 | low | present | |
| Del Rey | 0 | low | present | |
| Easton | 0 ( P ) | low | present | |
| Kearney Ag Center | 0 | low | present | |
| Kerman | 0 | low | present | |
| Kingsburg | 0 | low | present | |
| Sand Ranch | 0 | low | present |
Lake
Based on bud break, April 8, in Sauvignon Blanc , may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Kelseyville (KEL) | 0 | low | present | |
| Middletown (MID) | 0 | low | present | |
| Scotts Valley (SVL) | 0 | low | present | |
| Upper Lake (UPL) | 0 | low | present |
Madera
Based on bud break, March 13, in Thompson Seedless, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Firebaugh | 0 | low | present |
Mendocino
Based on bud break, April 17, in Chardonnay, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Ukiah-Ruddick (RUD) | 0 | low | present |
San Joaquin
Based on bud break, March 15, in Chardonnay, may need to adjust for other cultivars that emerge earlier than the indicated date. |
| Collegeville (COL) | 0 | low | present | |
| Escalon (ESL) | 0 | low | present | |
| Linden (LIN) | 0 | low | present | |
| Lockeford (LOC) | 70 | high | reproduces every 5 days | |
| Lodi (LangeTwins) | 0 | low | present |
P =
missing data substituted with values from previous day
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.