Minn-Dak Farmers Cooperative

Daily Infection Values:

Cercospora spores require leaf wetness to germinate and infect the leaves. Since the sensory technology for leaf wetness measurements are still being developed, the model utilizes relative humidity and air temperature measured within the sugar beet canopy to statistically correlate to disease occurrence. The current NDAWN Cercospora prediction model uses these relationships to determine favorable weather conditions for disease development as indicated by the DIV.

Daily Infection values (DIV) are determined from the total number of hours with relative humidity ≥ 85 percent in a 24 hour period (noon to noon) that were favorable for Cercospora development and the average air temperature during those hours. The noon to noon time period extends from noon yesterday to noon today and carries today's date. Daily infection values range from 0 (unfavorable) to 7 (very favorable). Generally the DIV increase with increasing number of hours of relative humidity ≥ 85 percent and with increasing temperature.

The NDAWN DIVs are presented in a graphical format and are based on the Two-Day Total Infection Value. If the Two-Day Total Infection Value ranges from 1 to 3, the infection risk is "Slight"; when the Two-Day Total ranges from 4 to 6, the infection risk is "Moderate", and when it ranges from 7 to 14, the infection risk is "Severe". A severe infection risk means conditions were extremely favorable for Cercospora development.