The Corn Disease Working Group has prepared an updated table of efficacy ratings for corn fungicides.
This table only provides efficacy ratings for diseases. It does not rank fungicides for physiological “plant health” effects.
Diseases of primary concern to us in Kentucky would include gray leaf spot and, sometimes, Northern leaf blight. In selected fields in some years, southern rust may justify a fungicide application under Kentucky conditions, but in most fields, levels of southern rust are so low that routine fungicide application is difficult to justify.
It would be very uncommon for the other diseases listed to pose yield-impacting threats under Kentucky conditions.
This table is a “work in progress,” so efficacy ratings are subject to change, should ongoing research indicate that changes are justifiable. In the meantime, these ratings may be useful to corn producers.