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Get Ahead of Fungal Diseases That Might Impact Next Year’s Corn

LeRoy Toohey

Nov. 12, 2019

With harvest wrapping up across most of the corn belt, it’s time to start thinking about next season’s input needs. One of the best ways to build your plan for next year is to consider what happened this season. Let’s look at the fungal diseases you may have seen this year and discuss what you can do to better prepare yourself for the next season’s crop. 

What to Look Out For

Growers in the southern regions already understand that many fungal pathogens overwinter, due to milder winters. There are a few that survive in southern area, but generally can’t overwinter in the northern climates. These are blown northerly from overwintering sites in the south during the growing season. This includes: 

  • Common Rust (Puccinia sorghi)

  • Southern Rust (Puccinia polysora)1

  • Southern Corn Leaf Blight (Bipolaris maydis)2

Some fungal pathogens overwinter in the northern and southern climates. Major examples are:

  • Northern Corn Leaf Blight (Exserohilum turcicum)

  • Northern Corn Leaf Spot (Bipolaris zeicola)

  • Gray Leaf Spot (Cercospora zeae-maydis)

  • Anthracnose Leaf Blight (Colletotrichum graminicola)1

  • Tar Spot (Phyllachora maydis)5

There are others that can overwintering in northern climates to a lesser degree, such as:

  • Diplodia Leaf Streak (Stenocarpella macrospora)

  • Physoderma Brown Spot (Physoderma maydis)

  • Eyespot (Kabatiella zeae)1

  • Common Smut Fungus (Ustilago maydis)

  • Head Smut Fungus (Sphacelotheca reiliana)4

Prepare Now for Next Year’s Crop

Hopefully, you’ve had a chance to scout your fields to identify fungal disease that may have impacted your crop this year. To be clear, fall scouting is the best way to prepare for the upcoming season.

Many fungal diseases can be minimized by turning crop residue under with tillage practices. By burying infected residue, many fungal pathogens can’t survive, making the time of infection shorter the following year. Tillage works well on many fungal pathogens, but it does not completely eradicate the problem. 

If you utilize minimum tillage or no-till, expect fungal pathogens to potentially return. Focus on crop rotation and reducing host plants in weedy areas or fence lines. Corn is a grass, and grasses that grow next to your fields or in weedy areas of your fields can provide a place for pathogens to survive and possibly infect your upcoming crop.

Another option to consider is limiting stressors that weaken the crop. Soil compaction, cold soil temperatures early in the season, excessively wet spring soils, soil fertility and seed treatment all contribute to a plant’s ability to fight pathogens later in the season. 

And don’t forget about genetic resistance. Most seed companies capture ratings from poor to excellent on common fungal pathogens. Understanding these ratings will help you balance fungal resistance with yield expectations. 

Develop a Chemical Plan That Protects Your Bottom Line

Products utilizing active ingredients such as azoxystrobin, propiconazole or tebuconazole work well against these fungal pathogens. This includes fungicides such as Quadris® or Quilt Xcel®, Tilt® and Custodia® (and generic equivalents).Timely scouting and timely applications can greatly increase your bottom line. Remember to always read and follow label instructions for control of each fungal pathogen in your fields.

Foliar disease impacts corn plants at a different rate every season, but understanding which pathogens we can suppress with tillage this fall and which ones overwinter in your area will greatly help you prepare for 2020.

PRO TIP: Foliar diseases that are not fungal pathogens, but sometimes get confused as fungal disease, include: 

  • Stewart’s Wilt (Pantoea stewartii), which overwinters in the corn flea beetle, 

  • Goss’s Wilt and Blight (Clavibacter michiganensis subsp. nebraskensis), which overwinter in residue borne bacterium1

  • Maize Dwarf Mosaic Virus3

  • Holcus Spot6

Fungicides have no effect on bacterial or viral pathogens, so save your money and focus on genetic resistance when selecting seed varieties.

Scout Your Fields with Greater Insights

As we mentioned, scouting your fields is a must if you want to stay ahead of fungal diseases in next year's crops. You can up your scouting game utilizing precision maps and data specific to your farm and fields. 

QuadrisⓇ, Quilt XcelⓇ and TiltⓇ are registered and unregistered trademarks of Syngenta. CustodiaⓇ is a registered trademark of an ADAMA Group Company.

Sources: 

LeRoy Toohey

Nov. 12, 2019

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