Signup to receive email updates




or follow our RSS feed

Blog Archives

288 Total Posts

follow our RSS feed

Blog Banner

Around the County

Frequent information updates for agricultural audiences
Diplodia ear rot

Diplodia Ear Rot - from Loretta Ortiz-Ribbing

Posted by John Fulton -

I am not sure how much more rain to expect this season, but I have had enough. I also know that diseases love the wet weather. This season we had a wet July, a dry August, and now a very wet September. The wet July weather that occurred after and during the corn silk stage has probably contributed to the development of Diplodia ear rot that has been found in corn fields since late August. Planting corn after corn and minimum tillage also favors development of this disease, because the organism causing disease survives in corn stalks left on the field from the previous year.

Often the fungus causing Diplodia ear rot will infect the ear just after flowering which causes the husk and the ear leaf to appear bleached and brown, compared to the normal green color of the remaining leaves. If the husk leaves are pulled back to expose the ear and kernels, the ear may appear shrunken and gray-brown in color, while infected kernels will be surrounded by a dense mass of white fungus that fuses the kernels to the husk leaves. The white moldy growth often begins at the bottom of the ear, and if infection occurred early could cover the entire ear or only a portion of the ear if infection happened later. As the season progresses, the white moldy growth will turn gray-brown and small, round, black specks (fungal fruiting bodies) will form scattered about on the husk and kernels.

While the fungus causing Diplodia ear rot will not produce a toxin in the grain, like ear rots caused by Fusarium or Aspergillus fungi, it will cause the grain to be light weight, shriveled, and have lower nutritional value for livestock. Usually this ear rot is not a problem in stored grain, but infected grain should be dried to below 15% moisture to prevent growth by this fungus in storage. A good description and photos of ear rots can be found in the 2007 issue, volume number 21, article 3 of The Bulletin at http://ipm.uiuc.edu/bulletin.

Diplodia is not as common as other ear rots, but in wet years like this one, it can be a problem. Management options are limited but include crop rotation and selecting less susceptible hybrids for next year. Talk with your seed dealer, as corn hybrids differ in their susceptibility to Diplodia.

The wet, cool weather poses other harvest concerns, such as lodging of corn in wet soil, being able to get equipment into the wet fields, and the ability of grain to mature and dry. Along with these concerns, I suggest being vigilant about scouting for stalk rots. If Diplodia ear rot is present, this same organism may show up in the stalks as well. The base of corn stalk with Diplodia stalk rot will have small, black specks embedded in the plant tissue. There will be no pink color and the black specks will not rub off as with Gibberella stalk rot. White mold like that seen on the ear kernels may be found in lower stalks but not always, and splitting the stalk in half may reveal internal shredded plant tissue with small, black specks (fungal fruiting bodies).



Please share this article with your friends!
Share on Facebook Tweet on Twitter Pin on Pinterest