Disease Model Notes
BASICS
Leaf Wetness:
Most of the disease models require leaf wetness, but the available weather data does not include leaf wetness. GrapeCast uses an algorithm to determine leaf wetness. More can be seen (and tested) here.

Missing Data:
The models listed below require hourly weather data 24 hours a day, 365 days a year. For the lost part connections on the internet today are reliable enough to usually deliver. But from time to time disruptions occur, preventing this. Any missing data is replaced with data inferred from adjacent readings. This is noted as both 'Hours Missing' and is a part of the stations Reporting History. This needs to be taken into account when using the disease alerts as a guide for pesticide applications.

POWDERY MILDEW MODEL
If there are at least 6 consecutive hours with temps between 70 and 85, add 20 points to the Alert Index.
If not, subtract 10.
Also, if the temp ever gets above 95, also subtract 10.
- POWDERY ALERTS (based on Index value):
- None (green): risk factor = 0
- Low (yellow): risk factor >0 & <30
- Moderate (orange): risk factor >=0.5 & <1.0
- High (red): risk factor >1.0

DOWNY MILDEW MODELS
- Primary Infection:
   Primary infection only requires 0.39" of rainfall in a 24 hr period.
- Secondary Infection
   A secondary downy infection requires 4 hours in complete darkness with a minimum of 97% humidity @ 55 degreesF or greater.
   Civil Twilight is used to determine sunset and sunrise times.

BLACK ROT MODEL
If the humidity is over 89% for a 1 hr period, a risk factor is given based on the temperature:
>=50 & <55 - risk factor = .04
>=55 & <60 - risk factor = .08
>=60 & <65 - risk factor = .11
>=65 & <70 - risk factor = .13
>=70 & <80 - risk factor = .14
>=80 & <84 - risk factor = .17
>=84 & <90 - risk factor = .11
Greater than 90 - risk factor = .08
The risk factor is added until there is a period of 9 hrs of dryness (no leaf wetness). This ends a current infection period.
The risk alert is determined as follows:
None (green): risk factor = 0
Low (yellow): risk factor between 0 & .5
Moderate (orange): risk factor between .5 & 1.0
High (red): risk factor of 1.0 or greater

PHOMOPSIS MODEL
If the temperature < 54F then run the model as if the temperature = 54F.
If the temperature > 90F < 104F then run model as if the temperature = 90F.
If the temmperature > 104F then time interval is not conducive to infection and is ignored.
Then the temperature is inserted in the following formula:
The infection index = (0.061601 * # of wet hours * temp) - (0.001511 * # of wet hours * pow ((temp), 2)) - (0.374927 * # of wet hours) - 2.647866;
The risk alert is determined as follows:
None (green): risk factor = 0
Low (yellow): risk factor between 0 & .5
Moderate (orange): risk factor between .5 & 1.0
High (red): risk factor of 1.0 or greater

BOTRYTIS MODEL
A warning is issued when any of the following occur during a period of leaf wetness:
Ave Temp for 12hrs: >=46 & <50
Ave Temp for 11hrs: >=50 & <54
Ave Temp for 10hrs: >=54 & <55
Ave Temp for 09hrs: >=55 & <59
Ave Temp for 08hrs: >=59 & <61
Ave Temp for 07hrs: >=61 & <64
Ave Temp for 06hrs: >=64 & <68
Ave Temp for 05hrs: >=68 & <70
Ave Temp for 04hrs: >=70 & <81
Ave Temp for 05hrs: >=81 & <86
Ave Temp for 07hrs: >=86 & <87

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