Mildew Risk Models

To add either Mildew models to a site, follow the below steps:

1. Find your site in the sites list and select the spanner icon

2. Add sensor, search "Calculations & Agronomic Derivations" - select use

3. Go to the drop down in Select input type

4. Choose the appropriate Mildew Model

5. Map the temperature input and unit of measure

6. Select Add Sensor To Site

Gubler-Thomas powdery mildew model - UC Davis

The Gubler-Thomas Powdery Mildew Risk Index, developed at UC Davis, provides a useful tool to make smart decisions regarding preventative fungicide sprays based on the weather and optimum temperatures for conidial reproduction. The model uses these temperature thresholds to calculate a daily (0–100) risk index which can be used to adjust intervals between sprays.

• An index of 0–30 indicates low risk of disease. Chemical fungicides may be used at intervals of 21 days, or label max, and sulfur may be used at 14–21 day intervals.

• An index of 40–60 indicates moderate risk of disease.Chemical fungicides may be still be used at intervals of 21 days, or label maximum, at this risk index, but sulfur,if used, should have a reduced interval rate of 10–17 days.

• Above 60 indicates high risk which should results in a 14 day interval, or label minimum, for chemical fungicides, and 7 days for sulfur.

Risk calculation:

• If ( 70°F (21.1°C) <= Temperature < 85°F (29.4°C) ) for more than 6 h then Risk += 20, else Risk -= 10

• If maximum temperature >= 95°F (35°C) then Risk -= 10

• If risk > 100 then risk = 100

• If risk < 0 then risk = 0

References: 
https://blog.pestprophet.com/how-to-use-powdery-mildew-risk-index-model-on-grapes/
https://www.apsnet.org/edcenter/apsnetfeatures/Pages/UCDavisRisk.aspx

https://blog.pestprophet.com/how-to-use-powdery-mildew-risk-index-model-on-grapes/#:~:text=The%20Gubler%2DThomas%20Powdery%20Mildew,optimum%20temperatures%20for%20conidial%20reproduction.&text=An%20index%20of%2040%E2%80%9360%20indicates%20moderate%20risk%20of%20disease

Gubler-Thomas strawberry powdery mildew model

Risk calculation:

• If maximum temperature >= 32°C then reduce risk by 10, else

• If ( 15°C <= Temperature < 25°C ) and humidity > 0.0 then increase risk by 20, else reduce risk by 10

• If risk > 100 then risk = 100

• If risk < 0 then risk = 0

Reference: 

http://info.metos.at/tiki-index.php?page=Powdery+Mildew+Risk+Model+for+Strawberries