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Early signs of corn ear molds

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With more variation in weather, there’s a chance you might observe a wider variety of ear molds in your fields. Additionally, years with more corn earworm — which creates easy entry points for diseases of the ear — may cause increased incidence in ear fungal diseases. 

There is no rescue treatment for ear molds, so it is important to identify fields with the highest levels of the disease to help determine if you need to accelerate harvest or harvest those fields first. As you’re scouting fields for signs of ear mold, keep in mind that although infection occurs early (several pathogens causing ear molds usually infect the plant from pollination to 21 days), symptoms do not usually appear until R5 (dent). Furthermore, ear molds continue to develop in the field even after the corn reaches physiological maturity and begins to dry down. Even after corn is harvested, molds will continue growing until the grain is dried to 13% to 15% moisture.

Signs of more common ear molds

  • White-colored fungus at base of ear. Especially if you’ve had a wet and humid growing environment, this could be the start of diplodia ear rot. As the disease progresses, the mold and kernels turn grayish or grayish-brown and may rot the entire ear. Although it doesn’t cause mycotoxins, it can reduce grain test weight and can result in significant docks at the grain elevator.
  • Pink to reddish color at the top of the ear. This is how Gibberella ear mold begins and, in highly susceptible hybrids, can affect the entire ear. Gibberella produces mycotoxins, vomitoxin and zearalenone, so the grain must be handled separately and tested for contamination.
  • White- to light pink-colored fungus on scattered kernels, especially those damaged by insects. Fusarium ear rot starts by infecting the corn ear in patches or on single kernels. The kernels then turn tan or brown, and the mold appears to be white, gray or pink in color. One of the three species of fungi causing fusarium ear rot also produces mycotoxins.

The symptoms for all three of these species are similar, so if you spot any of these early signs, a laboratory test is needed to identify the infecting fungus.

Signs of less common ear molds

  • Thick green mold growing on and between kernels. This could be Trichoderma, which usually stems from damage, either by birds, insect feeding or mechanical injury. It does not produce mycotoxins but will affect grain quality.
  • Gray-green powdery mold. Particularly in hot, dry years, this could indicate Aspergillus ear rot. It produces a mycotoxin, known as aflatoxin, so the corn should be handled separately and tested.

Weekly scouting for signs of corn ear molds is important as harvest nears. If weekly timing is a challenge on your farm, your local Mycogen Seeds team or ag retailer can help you prioritize hybrids to scout.

Early signs of corn ear molds

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