The Only Thing Missing for Crop Disease is Heat

CROP WATCH: The field has plenty of moisture even when it's not raining.

Published on: Jul 8, 2013

The Crop Watch '13 field of corn is somewhere between knee high and waist high, probably pushing waist high, at least on an average-sized person. Checking it the other morning about 9 a.m., I noticed that most of the leaves were shiny. The shiny appearance turned out to be moisture, and there were even drops of water pooled on some leaves.

It hadn't rained for a couple days. The moisture was there because of the humidity and cool weather for very late June. Normally, that much moisture on corn leaves at that stage would spell trouble with foliar diseases. They may come, but I didn't see a lesion in my walk through the field.

What's missing is heat, experts say. Most diseases need a susceptible host, moisture and heat to get a foothold on their target crop. The corn is there, the moisture is certainly there, but at least until now the heat has been lacking. Even though May wound up above average on temperature, it didn't feel like it because there were very few hot days. Most days hovered at just above or below average. Then June brought cool weather again.

CROP WATCH: The field has plenty of moisture even when its not raining.
CROP WATCH: The field has plenty of moisture even when it's not raining.

The lack of lesions may be partly because the hybrid is resistant to most leaf diseases. However, if conditions were right you would still expect to find at least a few lesions.

Gray leaf spot is often a culprit, but agronomists say it definitely needs warm weather to flourish. If any disease of the foliar variety on corn would have a shot at showing up in these conditions, it would likely be northern corn leaf blight. Still, it needs a certain amount of heat to spread and do well.

The season has a long way to go. Scouts advise keeping an eye out. Right now, though, there aren't many diseases in corn fields we've checked.

Plenty of moisture: These are conditions disease pathogens like, but they dont like cool weather. They need warmer weather to take off and develop lesions.
Plenty of moisture: These are conditions disease pathogens like, but they don't like cool weather. They need warmer weather to take off and develop lesions.