Watch for diseases, insects in corn, soybeans

Tony Nye - OSU Extension

With the wacky planting and growing season we have had thus far in 2019, I want to encourage producers to scout fields for disease. Our late planting season this year can make our crops more vulnerable to higher levels of disease according to Ohio State University agronomy specialists.

The dry weather lately has helped hold back disease development in some cases since many diseases need moisture to survive and thrive. With that said it is still important to be watchful for disease and insects as well as some molds.

Our experts at Ohio State University remind us that fungal diseases that can infect soybeans or corn can survive through the winter on crop residue left after harvest can cause the onset of disease again in the spring and spread. When we have a delayed planting year like this year, the disease spores carried over have more time to multiply.

Pierce Paul, Ohio State University plant pathologist, notes that not only are more spores potentially available to infect corn and soybean plants, but because in a late planted year like this, these spores can infect plants in a much earlier growth stage increasing the potential for more impact on the growing plants.

Right now it appears that gray leaf spot is the most commonly found in fields but producers should also be on the lookout for Northern corn leaf blight and a new disease in Ohio tar spot. All three diseases are potential threats to this year’s crop.

In soybean fields, frogeye is the disease to be most concerned about.

The incidents of this disease has been increasing every year in Ohio and we must keep in mind that is was severe in some cases late last growing season here in Clinton County.

Anne Dorrance, Ohio State University plant pathologist reminds producers that if frogeye leaf spot is found on a soybean plant just before or during the growth of the bean pod, it could create significant yield loss if not controlled. Dorrance also suggests that cercospora leaf blight and downy mildew, a water mold, are also potential threats to this year’s crop.

Phomopsis is another disease to be watchful of and remember it was a major problem throughout Ohio last year.

We know there are some varieties of corn and soybeans that are resistant to a variety of diseases, so a grower would know which fungal diseases he/she would have some protection from but keep in mind resistance does not mean immunity, it only means that damage to a resistant plant will be milder according to Dorrance.

Crop specialists suggest walking your field more frequently this year so you can stay on top of any diseases progressing in a given field. Don’t forget to also be watchful for insects and the potential for damage to crops.

One insect we have been on the lookout this year has been the brown marmorated stink bug in soybean fields which was a big problem this year. We have been monitoring for stink bug in Clinton County this growing season and it has proven they are out there but insect trap numbers have been low here and in other counties thus far.

No matter the disease or insect issue, understand the threshold the crop can tolerate before impacting revenue lost from less yield and do your homework on which pesticide will provide the best control.

For more information about disease or insect threats on late-planted crops, visit the following:




Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for over 30 years, currently serving Clinton County and the Miami Valley EERA.

Tony Nye

OSU Extension