Disease risk by block
Mildew risk for every block, so you spray when it matters
Vineyard mildew risk models turn weather into an infection risk, so you time a spray on the disease rather than the calendar. GrapeFlow runs them for every block of your vineyard from modeled weather at the block’s location: a daily downy mildew and powdery mildew risk for the past week, today and the next three days — the powdery mildew model based on the Gubler-Thomas (UC Davis) index, downy mildew from rain, temperature and estimated leaf wetness. In an organic vineyard, every pass you skip is labor and diesel you keep.
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What GrapeFlow models, block by block
Powdery mildew — based on Gubler-Thomas
Hours in the temperature band the fungus likes, heat that kills its spores and rain that washes them off, turned into a daily 0–100 risk for each block. It follows the logic of the UC Davis index; it is GrapeFlow’s operational score, not the index itself.
Downy mildew — infection events and incubation
A daily risk plus the primary infection events behind it (rain, warmth and a long wet spell), each with an incubation countdown to when symptoms can appear — and a gate that waits for overwintering spores to mature before calling the first one.
Botrytis near harvest
A heuristic for bunch rot after veraison, from rain and humidity, so a late-season storm is on your radar before it is in your bins.
Weather you don’t have to install
Hourly modeled weather for each block’s coordinates — temperature, humidity, dew point, rain and wind. Leaf wetness is estimated from those, not measured, and the screen says so.
Protection from your last spray
GrapeFlow reads your spray log: copper counts against downy mildew and sulfur against powdery mildew, for at most two weeks and ten days, cut short by the rain since. Each block shows as protected, partly protected or exposed — an estimate that knows nothing of coverage or new growth.
How the Gubler-Thomas index works
The UC Davis powdery mildew risk index, developed by Doug Gubler and colleagues, reads canopy temperature. After the first ascospore infections, three consecutive days with at least six continuous hours between 70 °F and 85 °F start an epidemic; from then on, each day with six such hours adds 20 points, a day without them takes 10 off, and a spell above 95 °F for more than 15 minutes knocks the index down. It runs from 0 to 100.
UC IPM ties spray intervals to it: for sulfur, about every 14–21 days at low pressure (0–30), 10–17 days at moderate (40–50) and 7 days at high pressure (60 and above). Longer intervals at low risk are where the passes are saved.
Deciding the next spray
The model tells you how much pressure there is. Whether a block needs a spray today is still your decision:
Read the block’s risk for today and the next three days. Low and staying low: wait and look again tomorrow. Rising or high: a spray window is coming.
Ask whether the last spray still protects the block. GrapeFlow estimates it from your spray log and the rain since. Contact products only protect what they covered, so fast shoot growth or a product it can’t classify is your call: check the date and product in your log.
For downy mildew, look at the infection events. A primary infection event means a protective spray should already be on, or go on before the next rain. The incubation countdown tells you when to scout for oil spots.
Check REI and PHI, then spray and log it. Log the application by block with the product’s EPA number, rate per acre, REI and PHI — the record your auditor and your crew both need.
Use the risk alongside what you see in the rows. The models run on modeled, not measured, weather and do not replace scouting.
Your blocks, or your region
This page is about the per-block risk inside GrapeFlow. The free Disease risk pages show region-by-region forecasts for powdery and downy mildew across US wine regions — a good first look before you set up your own blocks.
One price, everything included
$99/month, or $990/year. Vineyard and winery records, and the US compliance set, are all included. No per-seat pricing. 30-day free trial, no credit card.
Start your 30-day free trialFrequently asked questions
How does GrapeFlow calculate powdery mildew risk?
From hourly modeled weather at each block’s location: hours in the temperature range the fungus favors, heat that kills its spores and rain that washes them off, combined into a daily 0–100 risk. The model is based on the Gubler-Thomas (UC Davis) index, but it is GrapeFlow’s own operational score rather than the index itself.
Is leaf wetness measured?
No. Leaf wetness is estimated from modeled temperature, humidity, dew point and rain. GrapeFlow needs no weather station, and every risk carries a note that it is an estimate.
Does GrapeFlow know whether my block is still protected by the last spray?
Approximately. GrapeFlow reads the applications in your spray log — copper against downy mildew, sulfur against powdery mildew, other fungicides more loosely — and estimates the protection left from the days and the rain since: at most two weeks for copper and ten days for sulfur. It does not know how good the coverage was or how much the canopy has grown since, so treat it as a prompt, not a guarantee.
How far ahead does the risk look?
The past seven days, today and the next three days for every block, with downy mildew infection events found up to 30 days back so their incubation can be followed.
Is this the same as the regional disease risk pages?
No. The disease risk pages show free regional forecasts for US wine regions. Inside GrapeFlow the risk is computed for each of your own blocks, at its own coordinates.
How much does GrapeFlow cost?
$99/month or $990/year, with every module included and no per-seat pricing. There is a 30-day free trial and no credit card is required.