Corn watch: Fusarium crown rot on the rise

“Fusarium crown rot favors cool, wet environments, and the early growing season has set the stage for the disease to take hold this year,” says Bill Kessinger, technical agronomist for Stine^® Seed Company. “This is one that infects early, but we will not see the symptoms until closer to fall.”

While research on the disease continues to evolve, understanding the disease cycle and knowing what to look for can help growers better prepare for the season ahead.

Pathogen and disease development

Like Fusarium stalk rot, Fusarium crown rot in corn is associated with Fusarium spp. It’s an early-season disease that is thought to favor wet, compacted soils and is often exacerbated by midseason stressors, including excessive moisture, drought or corn rootworm pressure.

The fungus overwinters in soil and leftover crop residue and is thought to infect plants after the seedling stage. While it may impact the crop early on, the greatest damage often appears during the reproductive process.

“Fusarium crown rot can be detrimental to plant health during a critical stage in the crop’s development,” says Kessinger. “It essentially deprives plants of moisture and nutrient uptake during grain fill, leading to poor kernel development and yield loss. As the disease progresses into the stalk, standability and lodging become a concern.”

Symptoms and identification

Although Fusarium crown rot takes hold early, symptoms may not appear until later in the season, when standability can become a concern. Like many other crop diseases, early above-ground symptoms may include yellowing of the lower leaves or stunted plants, but the most telling signs are found in the crown, roots and stalk.

“After ear development, the pinch and push test can help determine if the disease is present, along with the severity of the disease and any standability issues with the crop,” says Kessinger. “I typically recommend that growers perform the test on the section of the stalk that falls below their knees. If it’s hard, it’s still good. If it pinches together easily and appears soft and hollow, it may be a Fusarium-based issue.” 

The pinch or push test is a common practice to gauge disease presence and standability issues in corn. Pinching the stalk reveals the condition of the tissue inside, while pushing tests the stalk’s structural strength. If it buckles or bends under pressure, it’s a clear indicator that the plant has been compromised and lodging is a likely risk.

“If there’s little to no stalk strength left, then you should split the stem to see if it’s hollowed or if the tissue is dark brown and decaying,” notes Kessinger. “If it’s missing that nice white vibrant color, Fusarium crown and/or stalk rot is a likely culprit and lodging and harvestability should be your next concern.” 

Beyond standability, as the disease progresses, it can compromise the plant’s ability to take up vital nutrients and water, particularly during grain fill. As a result, kernel loss and plant death may occur. The Crop Protection Network notes that infected plants may also senesce, or die prematurely. Sometimes they are referred to as “ghost plants” at this point because of their grayish-green discoloration.

Because several diseases can produce similar symptoms, getting a second opinion is essential before deciding next steps.

“When in doubt, it’s best practice to send a sample to a local laboratory to confirm the disease,” says Kessinger. “Doing so can help determine the right fungal pathogen causing the issue, like Fusarium, which can help determine the proper next steps, whether that’s a pass with a fungicide or soil management strategy like tillage.”

Current management strategies

Experts are still working to better understand the best management strategies to combat Fusarium crown rot, but current recommendations include a combination of crop rotation, tillage for residue management, staggered planting dates, fungicides, biologicals and seed treatments, and hybrids with elevated Fusarium tolerance.

Unfortunately, because Fusarium crown rot develops at and below the surface, foliar fungicide applications are not known to be as effective. Stine agronomists recommend a management plan that includes seed treatments and crop rotation to help reduce disease pressure in future seasons.

“The effectiveness of fungicides to manage Fusarium crown rot is still being researched,” says Kessinger. “That said, if growers opt to try a fungicide this year, it’s recommended to do so before V7. A more long-term strategy should include breaking up that residue after harvest, hybrid selection for lines with elevated Fusarium tolerance, and a biological seed treatment like Stine XP^® SureFlow, which helps protect the seed from the start.”

Stine XP SureFlow is a concentrated planter box lubricant that supports early plant health, from root development to nutrient efficiency during the crop’s critical growth stages. It integrates macro- and micronutrients to promote early root development and uniform emergence while also introducing humic and fulvic acids to enhance nutrient availability and soil interaction in the seed zone.

“While there’s still a lot we have to learn about Fusarium crown rot, just like any disease, the best you can do now is scout often, do your research on the disease, and lean on a trusted agronomist or university extension expert to help map out a plan to manage the problem,” stresses Kessinger.

He also recommends growers leverage resources such as the Crop Protection Network’s Crop Risk Assessment Tool, which uses weather-based forecasting to provide crop disease risk assessments that support more informed management decisions.