Excessive Heat Stress to Corn "Down Under"

Bob Nielsen, Extension Corn Production Specialist
Department of Agronomy, Purdue University

Stress to corn from excessive heat is not usually on the top of my list of frequent problems faced by Indiana corn growers every year. The main reason for this is that Indiana does not usually experience high enough air
temperatures during the summer to cause true heat stress in corn. True heat stress to corn usually occurs in more western or southwestern areas of the U.S. Corn Belt or in corn-producing areas around the world such as
Australia. On a trip "down under" in 2003, I saw first-hand the consequences of severe heat stress on irrigated corn in New South Wales. The farmers reported that the crop had experienced a week or more of 122+ F air
temperatures just prior to pollination that was accompanied by severe drying winds. Frequent irrigation by center pivot was not able to "keep up" with the transpiration demands of the crop. The symptoms of the excessive heat stress included complete death of much of the upper leaf canopy, complete to nearly complete arrest of ear development, and extensive kernel abortion.

Click images to enlarge

Closer view of damaged upper leaf canopy

View of whole plants

Closer view of dead leaf tissue

Arrested ear development

Kernel abortion on ear

Closer view of aborted ears