Corn Disease

Risk of Corn Grain Contamination with Vomitoxin in Ohio in 2024: July 8 Projection

Article taken from https://agcrops.osu.edu/newsletter/corn-newsletter/2024-22/risk-corn-grain-contamination-vomitoxin-ohio-2024-july-8 by Jason Hartschuh, CCA, Pierce Paul, Stephanie Karhoff, CCA

Mycotoxins, specifically deoxynivalenol (DON), commonly referred to as vomitoxin, has become a significant problem for Ohio corn growers. What was once considered an every-ten-year problem, has now become a yearly challenge in some sections of the state. DON contamination of grain is often associated with Gibberella ear rot (GER), a disease caused by the fungus Fusarium graminearum. The Ohio State University Cereal Pathology Lab led by Dr. Pierce Paul has been researching and developing weather-based models to predict when weather conditions are favorable for DON contamination of corn grain. The current models have an 80% accuracy at predicting when conditions are favorable for grain to be contaminated with at least 1 ppm DON, meaning that based on data collected so far, the models are correct about 8 out of 10 times at predicting whether DON contamination will reach or exceed 1 ppm.

The fungus that produces DON infects corn ears during pollination while silks are wet (R1 growth stage). Each week, we will be updating the models and share estimates of the chance of grain in various parts of the state being contaminated with at least 1 ppm DON. This information will be made available through the C.O.R.N newsletter. Predictions generated by these models should only be applied to corn pollinating during the model’s prediction model’s prediction window, which is specific for each area of the state and field within that area. As a result, each week predictions will likely change for the corn that is pollinating based on changes in weather conditions. Similarly, during any given week, predictions will likely change from one field to another based on hybrid maturity, planting date, and weather condition, all of which affect the silking/pollination window.

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Tar Spot confirmed in Paulding County

Tar Spot was confirmed in Paulding County on September 7, 2021.

This week Tar Spot was confirmed in a cornfield in Paulding County. Below is a picture of what to look for when scouting for Tar Spot.  For more information on Tar Spot please see the links:

  1. https://crop-protection-network.s3.amazonaws.com/publications/tar-spot-filename-2019-03-25-120313.pdf 
  2. https://agcrops.osu.edu/newsletter/corn-newsletter/22-2021/tar-spot-showing-early-year-note-diagnosis
  3. https://agcrops.osu.edu/newsletter/corn-newsletter/2021-30/tar-spot-more-widespread-cross-state-ohio-2021

Thanks,

Gibberella Ear Rots Showing up in Corn: How to Tell It Apart from Other Ear Rots

Author(s): Pierce Paul, Felipe Dalla Lana da Silva

Over the last two weeks, we have received samples or pictures of at least two different types of corn ear rots – Gibberella and Trichoderma. Of the two, Gibberella ear rot (GER) seems to be the most prevalent. Ear rots differ from each other in terms of the damage they cause (their symptoms), the toxins they produce, and the specific conditions under which they develop. GER leads to grain contamination with mycotoxins, including deoxynivalenol (also known as vomitoxin), and is favored by warm, wet, or humid conditions between silk emergence (R1) and early grain development. However, it should be noted that even when conditions are not ideal for GER development, vomitoxin may still accumulate in infected ears.

A good first step for determining whether you have an ear rot problem is to walk fields between dough and black-layer, before plants start drying down, and observe the ears. The husks of affected ears usually appear partially or completely dead (dry and bleached), often with tinges of the color of the mycelium, spores, or spore-bearing structures of fungus causing the disease. Depending on the severity of the disease, the leaf attached to the base of the diseased ear (the ear leaf) may also die and droop, causing affected plants to stick out between healthy plants with normal, green ear leaves. Peel back the husk and examine the suspect ears for typical ear rot symptoms. You can count the number of moldy ears out of ever 50 ears examined, at multiple locations across the field to determine the severity of the problem.

Ear rot symptoms

Continue reading Gibberella Ear Rots Showing up in Corn: How to Tell It Apart from Other Ear Rots →