Doc. # 7430-0710-01 Rev. C
Page
104
9.3 Powdery Mildew (Conidial)
In order for the powdery mildew epidemic to begin, the pathogen requires three consecutive days
when there is a minimum of 6 hours of temperatures between 21 and 30°C. If three consecutive
days at these temperatures are not met, the index reverts to zero. For each day that this
requirement is met, 20 index points are assigned. After 3 days, an index of 60 would be achieved
thus triggering the index. Once the 3 consecutive day requirement is met, it no longer is a
function of the model. The model will fluctuate between 0 and 100. Losing 10 points on days
when the 6 hour requirement for 21-30°C was not met or if at any time during the day, the
temperature rose to 35°C for at least 15 min. An index of 60-100 indicates the pathogen is
reproducing every 5 days while an index of 0-30 indicates a reproductive rate of 15 days or less.
An index of 40-50 is considered normal and would imply a reproductive rate of 8-11 days, i.e.,
somewhere between a 5 and 15 day reproductive rate.
Refer to the website
http://www.apsnet.org/online/feature/pmildew/
for further details.
Configuring the Powdery Mildew (Conidial) Calculation
All configuration parameters are the same as the Chill Hours except the temperature thresholds
are predetermined by the model.
9.4 Powdery Mildew (Ascospore)
The ascospore portion of the model forecasts ascospore release based on leaf wetness and
temperature. This requires a Leaf Wetness sensor such as the ACEINNA eS1301.
