For the last 30 years, each fall, I have checked cornfields in the county (Butler County, Ohio) to get an idea of the problems in those fields at harvest, and to try to determine yields. This information, along with input data from the producer, is presented at a winter meeting.

We talk about the practices that work and that are the most profitable in our cornfields. It is great to see how changes in our fields have helped to keep our farmers more profitable, but that is a topic for another day.

From November 1 to November 8, I checked eight fields and every one of them had problems, in varying degrees, with stalk quality and ear rots. In a couple of the fields, at least 30 percent of the stalks were lodged.

Even in the fields where most of the stalks were still upright, the pith of most plants had suffered damage and it is just a matter of time before many of those plants will also be flat on the ground.

In at least one of the fields, approximately 60 percent of the ears had been affected by ear fungi. As of November 10, I would estimate that we have about 50 percent of our corn harvested in Butler County. That means there are a lot of acres that are still at risk.

While ear rots may be caused by several fungi, the most important ear rot problems in Ohio - Gibberella, Diplodia and Fusarium ear rots - are caused by some of the same fungi associated with stalk rots, Gibberella zeae, Steno-carpella maydis and several Fusarium species. So, the most important sources of spores for infection of the ears are cornstalk and earpieces left on the ground from a previous crop.

Some ear rot-causing fungi also reside in the soil. Under wet conditions, spores are produced on debris on the soil surface and are usually wind-blown or rain-splashed to the ears.

When lodging occurs, infection is greatly facilitated by the fact the ears are closer to, or come into direct contact with, the fungi on infected debris. In addition, infection is further favored by the fact that ears in contact with the ground often remain moist. Moisture favors the development of ear rots.

During silking and early grain development, when the ears are most susceptible to infection, the ear rot fungi usually penetrate the ear via the silk channel. Later in the season, however, infection mostly occurs at the base of the ear where the fungi penetrate the husk. Late season ear rot development is favored by rainfall prior to harvest, especially when the ears do not turn down and water collects at the base of the ear between the husks and the kernel.

Poor growth conditions during the early part of this season may have prevented kernels from developing fully in some fields. Poorly developed ears (“beer can” ears) are more likely to remain upright than fully developed ears, and as a result, are more likely to develop ear rots.

In addition, whether the ears turn down or remain upright varies from one hybrid to another. Given the rains we have had, fields with poorly developed ears that do not turn down, hybrids with ears that dry in an upright position, and severe lodging may experience the greatest ear rot.

With ear rot comes the additional concerns of kernel rot and mycotoxin accumulation in storage. In addition to the physical damage caused by ear rots, some ear rot fungi produce mycotoxins that reduce the quality and value of the grain. Storage temperatures above 40 degrees F. and kernel moisture content of 22 percent and above are favorable for the growth of toxin-producing ear rot fungi (Fusarium species).

Growers are advised to follow certain harvest and storage guidelines to minimize problems associated with kernel rots and mycotoxin contamination:

•Dry harvested grain to 15 percent moisture and below to prevent further mold development in storage.

•Store dried grain at cool temperatures (36 to 44 F.) in clean, dry bins. Moderate to high temperatures are favorable for fungal growth and toxin production.

•Periodically check grain for mold, insects, and temperature.

•If mold is found, send a grain sample for a mycotoxin analysis to determine if toxins are present and at what level. Toxins are harmful to humans and livestock.

For more information on ear and stalk rots, got to www.butler.osu.edu and look for Hot Topics.

This farm news was published in the Nov. 22, 2006 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.