Exserohilum turcicum is able to infect the leavess of the mais plant when temperature and leaf wetness conditions are given. The time span to infect plant tissue is depending on the actual air temperature and leaf wetness period. The infection can take place, if temperature is ranging from 13°C to 28°C. At a temperature of 18°C it will need 18 hours for infection . If temperature is lower it will need even longer time and if it is warmer it will need a shorter leaf wetness period.
Northern Corn Leaf Blight (E. turcicum)
Infection model (Conditions):
START of the calculation of a NCLBinfection: If (leaf wetness > 0) and (air temperature >= 13) and (air temperature <= 28)
INCREASE : NCLBinfection actual :=NCLBinfection of the former hour +((air temperature-13)*leaf wetness duration in minutes).
STOP: no leaf wetness, temperature not in the optimal range or if NCLBinfection > (18-13)*18*60 then NCLBinfection = (18-13)*18*60. That means that in sum 5400 degreeminutes (= 90degreehours) could be reached than an infection is fulfilled (= (18°C- 13°C)* 18hours leaf wetness in minutes (18*60). At 18°C it needs 18hours leaf wetness for an infection. If temperature is higher or leaf wetness periods are longer it is still 5400 (all values above are 100% infection).
These models have been designed following the Report on Plant Diseases 202 - Common Leaf Blights and Spots of Corn by Mohammad Babadoost.
M. Babadoost is an Extension Specialist in Fruit and Vegetable Diseases, Department of Crop Sciences, University of Illinois at Urbana-Champaign