Foliar Fungicides for Corn

Producers may be considering spraying their corn with a fungicide.  Fungicides can be used to manage foliar diseases of corn to protect yield.  However, it should be noted that foliar applications of fungicides to corn will not always provide a yield increase of economic benefit. 

The main purpose of using a fungicide is to control a disease.  The problem is that by the time that you know a foliar disease is significant enough to cause economic loss, there is little you can do about it.  This leaves the producer in the dilemma of trying to outguess the disease situation or to just spray and hope for the best.

The producer can evaluate a cornfield’s risk of developing a severe foliar disease problem and increase the probability of an economic return on his fungicide dollars by considering the following:

  1. Previous crop and tillage practice – When corn was the previous crop and a substantial amount of residue is left on the soil surface, the risk of foliar disease increases.
  2. Planting date – Late planted corn is more at risk for gray leaf spot.
  3. Hybrid susceptibility – Hybrids with greater susceptibility are as greater risk.
  4. Weather and environment – High relative humidity and moisture are important for the development of foliar diseases.
  5. Disease observations – The earlier in the growing season that some diseases are apparent, the greater the risk of losing yield.

There have been reports of yield increases despite lack of disease pressure.  It is true that some fungicide classes, such as strobilurin fungicides can have other impacts on plants beside disease control.  One of the visual effects that can be seen on corn plants is a “greening effect”.  However in replicated trials, this has not always resulted in yield increases.

Foliar fungicides can help increase production and profits, if they are used appropriately.

Source: Joni Harper, MU Extension Agronomy Specialist