Southern corn rust has become an increasing concern for corn production in the U.S. in the past few years.

The cultivation of corn over vastly greater acreage in both Mexico and the lower Mississippi Valley has increased this potential threat in Kentucky. This is because the southern corn rust fungus can over-winter in corn fields in Mexico.

The increased acreage of corn in the lower Mississippi Valley increases the risk to Kentucky by creating a more effective pathway for the fungus as it spreads northward during the growing season via wind-blown spores.

Last week, Clayton A. Hollier, plant pathologist from Louisiana State University, reported finding southern rust in several locations in Louisiana. A detection this early in the Mississippi Valley is much earlier than what we have seen in the past few years.

Hollier also reported that observed disease levels were fairly low except in northeastern Louisiana, where a few fields had “medium to high levels” of southern rust. He expects the producers in northeastern Louisiana to treat with fungicide.

I would add that, even if those fields are treated, it is virtually certain that spores of the fungus have already been dispersed to other locations. Thus, it is worth being aware of this increased disease threat this season.

It isn’t known whether this very early detection of southern rust is related to climate change.

However, I spend a lot of time studying peer-reviewed scientific literature on climate change, and this is the very sort of thing that theory predicts.

Certainly the extremely mild winter has played a role in the earlier-than-normal activity of southern corn rust this spring.

Several Kentucky Extension agents have monitoring programs for southern rust in their counties. These programs will help us monitor this potential disease threat in Kentucky. Plus, providing real-time updates on regional disease progress also helps our neighbors to the north.

You can monitor the progress of southern rust at


It should be noted that this monitoring effort is not a funded project, so Extension agents and plant pathologists are not able to provide thorough and frequent geographic coverage.

However, any information on where southern rust is — even if incomplete — is more helpful to corn producers than no information

(You might also be interested in Diseases stealing profits from high-yield corn growers).