Look For Evidence of Corn Seedling Diseases Now
More than 90% of the 2023 corn crop was planted in 12 of the top 18 corn producing states by the end of last week, according to the USDA Crop Progress Report issued May 28.
With corn emerging and actively growing, agronomists are urging farmers to get out and actively scout fields for agronomic issues. Top of mind for many right now are seedling and early-season diseases.
Impact Of Dry Soils
Kirsten Garriott, LG Seeds National agronomy leader, says farmers on the Plains or other areas where conditions have been extremely dry, should be on watch for physiological plant responses to drought stress.
“Stress response and the consequences of fallow ground should be top of mind,” she says, in a press release. “Conversely, where some areas have received ample rainfall for the first time in several years, farmers should be on the lookout for disease and pest issues they may not have seen in a while.”
To help farmers with staging and scouting decisions, LG Seeds has published a Corn Scouting Guide. The free guide offers specific details, based on growing degree days and growth stages, that can help farmer determine when certain diseases, pests or nutrient deficiencies are likely to appear in their crop.
Learn more about the impact of dry weather here: Drought Tightens Grip Across the Corn Belt, 34% of Corn Now Hit with Drought
Stay On Top Of The Big 3
Corn seedling diseases, particularly Pythium, Fusarium and Rhizoctonia, are significant yield robbers that farmers often overlook because they operate underground.
Of the three, Pythium comes to the top of the list, according to Dale Ireland, technical product lead for Syngenta Seedcare.
“Pythium is the No. 1 seedling disease threat for corn, causing more damage than Fusarium and Rhizoctonia seedling diseases combined,” Ireland says.
Infection from Pythium (more than 50 known Pythium species exist) is favored by cool (<55 F), wet soil conditions.
Infections result in damping off — the leading cause of yield loss in corn, Ireland says — as well as “reduced plant stands, lower plant populations and reduced yield potential.”
Look For The Symptoms
Growers are often tipped off to Pythium’s presence when what were initially uniform fields of corn become erratic in plant height and growth stage—usually between the V1 and V3 growth stages, says Kyle Poling, Pioneer field agronomist.
He says four common signs Pythium is present are:
1. A plant whose top leaf growing out of the whorl is wilted or dead.
2. The entire plant is wilting.
3. The plant whorl is tightly wrapped and not opening.
4. There are gaps in the row where entire plants are missing.
The impact of Pythium in a crop is particularly critical at about the V2 corn growth stage, Poling says.
“This is a critical time in a corn plant's life as it's transitioning from the primary root system – comprised of the radical root and seminal roots – over to the nodal roots, the permanent root system, which will provide the bulk of the water and nutrients throughout the plant's life,” he says.
Poling adds that if the mesocotyl becomes diseased, it can be extremely difficult for a corn plant to smoothly and successfully transition to the nodal root system.
Younger Plants Fare Poorly
Several factors influence how well an infected corn plant will recover. Those include growth stage at the time of infection, growing conditions following infection, and plant vigor or early growth characteristics of the hybrid.
“Plants that are infected (by Pythium) at the V1 growth stage or earlier will have a tougher time developing the nodal roots than those plants at the V2, V3 or later growth stages,” Poling says.
Growth of infected plants that survive is usually stunted to the point they are at a disadvantage to compete with neighboring corn plants for light, water, nutrients, thus lowering yield potential, he adds.
Options For Prevention
For farmers looking to prevent seedling disease, including Pythium, agronomists recommend using a fungicide-containing seed treatment. Common options are those that contain metalaxyl or ethaboxam.
New and upcoming options to fight seedling disease:
1. Syngenta Seedcare recently introduced a novel mode of action to the marketplace with picarbutrazox, called Vayantis. Approved by EPA for use, the company says it offers the most robust Pythium protection ever, compared to existing oomycete protection molecules – metalaxyl or ethaboxam – based on extensive lab testing of over 400 Pythium isolates.
2. For 2023, Corteva plans to offer Lumiscend Pro fungicide seed treatment. It will be partnered with ipconazole fungicide seed treatment and L-2012 R biofungicide. The company says this combination will offer farmers two modes of action for pythium, three modes of action for rhizoctonia and fusarium, and one mode of action against head smut.
3. In the biological arena, DPH Biologicals just introduced a multi-action biofungicide seed treatment for use in 2023 - BellaTrove Companion Maxx ST - that helps seedlings fight pathogens and ensures healthy root systems. The EPA-registered OMRI-certified biofungicide and bactericide stimulates a plant’s natural defenses against pathogens while improving nutrient uptake and root health, the company says.
Plant pathologists increasingly recommend using two modes of action against Pythium along with integrated management practices. The combination is often necessary to prevent severe infestations, according to Nathan Mueller, University of Nebraska Extension agronomist. Even then, he adds, seedling disease “may still develop, such as during extended periods of inclement weather or severe pathogen pressure.”
Capture More Yield
Farmers in areas where corn crops are off to strong starts should make sure fertility isn’t a limiting factor, Garriott says.
“Finding nothing except good-looking corn when you’re scouting is just as important and impactful as finding something unusual,” she says. “Even if a field looks status quo, I encourage farmers to think about what they can do to intentionally manage toward top-end yield potential. Can you y-drop more nitrogen or is there a micronutrient opportunity? Look for anything that can take you up a level on that yield pyramid,” she adds.
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