30 May 2022
A photo of a LG Seeds employee checking corn for disease

How to spot (and mitigate) five of the most common early-season corn diseases

There’s unfortunately no shortage of early-season corn diseases that can ruin your yield. 

But that doesn’t mean you have to fall victim. Careful monitoring for early symptoms, developing a treatment plan, and thinking ahead (by planting resistant hybrids) can be the difference between lost yields and maximized ones. 

Here’s how to recognize, treat, and prevent five of the most common early-season corn diseases: 

Seedling Blight  

What causes it: Various fungal pathogens, including Diplodia, Fusarium, Penicillium, Pythium, and Rhizoctonia, combined with cool, wet weather.  

Photo of seedling blight in corn How to recognize it: Stunted plant growth, in the form of brown or shriveled mesocotyls. (Photo credit to Iowa State University)

Prevent and fight it: Do everything you can to keep your soil from getting damp or cool- Warm soils up with tillage, plant into 60°F temperatures (and above), and improve in-field soil drainage. You’ll also want to look into treating all seed corn with a fungicide. Ask your local sales rep or agronomist for the best treatment options for your specific hybrids. 

Anthracnose Leaf Blight 

What causes it: The fungus Colletotrichum graminicola, plus warm temperatures and extended periods of wet weather. Fields planted with corn in back-to-back seasons are also a risk, as the pathogen survives up to 10 months in infected residue. 

Photo of anthracnose leaf blight in corn How to recognize it: Brown, oval-shaped, up to half-inch-long lesions with yellow borders. They can also have fruiting bodies or setae (dark, thin, hair-like strands) in the centers. Bring out your magnification tools to identify the setae and keep an eye on development. Lesions can sometimes even merge, killing large portions of the leaf tissue. 
(Photo credit to Michigan State University)

Prevent and fight it: Consider crop rotation, so you can avoid getting burned by infected residue from the previous season. It’s also important to closely monitor fields that show symptoms of early-season infection. In the Western Corn Belt, June weather is often warmer and drier than May, which slows (or even stops) ALB development. But later in the season, top dieback or anthracnose stalk rot are possible.

Northern Corn Leaf Blight 

What causes it: High humidity (leading to damp leaves) and temperatures between 64 and 81°F. Conditions are especially ripe for this leaf blight in—you guessed it—the Northern Corn Belt. It’s one of the most common foliar diseases out there, and yield losses can be up to 30%.  

Photo of corn with tan lesions that are diseases (Northern corn leaf blight)How to recognize it: Long, cigar-shaped, gray or tan lesions. These usually start on the lower leaves and progress upwards. (Photo credit to University of Nebraska-Lincoln)

Prevent and fight it: Your best prevention strategy is to plant a corn hybrid with high tolerance to NCLB (reach out to your local LG Seeds agronomist for recommendations). Since NCLB overwinters in corn residue, you can also consider tillage and crop rotation. However, if the disease has already appeared in your fields, fungicide treatment will be necessary (spray at VT to protect the ear leaves before, during, and after pollination). It’s important to start treatment early at the first sign of disease—so make sure you’re scouting for symptoms frequently and early in the season.  

Holcus Leaf Spot 

What causes it: The bacterium Pseudomonas syringae pv. syringae, spread by wind-driven or splashing rain. It’s especially active in warm temperatures, too. 

Photo of holcus leaf spotHow to recognize it: Oblong, quarter-inch to inch-long lesions that look water-soaked, then eventually turn brown. These can resemble lesions from anthracnose leaf blight—but without the setae in the center.(Photo credit to University of Illinois)

Prevent and fight it: Unfortunately, since HLS derives from a bacteria, fungicides have little effect. Your strongest mitigation strategy is to plant a hybrid that offers specific resistance to HLS. Ask your local sales rep for recommendations, if HLS is a concern. 

Gray Leaf Spot 

What causes it: High humidity and warm temperatures. Springtime is especially dangerous, as wind or splashes of rain can transmit spores to corn plants.  

Photo of corn with gray leaf spot How to recognize it: Small, yellow-haloed lesions on the corn leaf are the first sign. These usually then transition into long, rectangular, dark brown or gray lesions running parallel to the leaf veins. The more of these spots a leaf has, the less leaf area is available for photosynthesis during critical growth stages, like grain fill.  

Prevent and fight it: Your best shot against GLS is a fungicide application at the VT-R1 growth stage. However, this is a particularly damaging corn disease. If you have a substantial outbreak before the VT stage, consider a second pass with a fungicide.  

If you’re looking for specific hybrids that offer increased resistance against these (and more) diseases, reach out to your LG Seeds agronomist or sales rep for advice on which are right for your fields, plus recommendations for any seed treatment options.