Q&A: Why are corn ears outgrowing their husks? - UNL CropWatch, August 19, 2011

Q&A: Why are corn ears outgrowing their husks? - UNL CropWatch, August 19, 2011

August 19, 2011

Corn ear outgrowing husk

Both genetics and environment can lead to corn ears outgrowing their husks.

Q.  Charles Shapiro, extension soil scientist at the Haskell Ag Lab at Concord:  In a couple of our trials the corn husks are not long enough to contain the ear. We have not seen much of this before. Attached are a few pictures. Any explanation?

A.  Tom Hoegemeyer, professor of practice in the UNL Department of Agronomy and Horticulture:   I have seen this many times over the years. There are two factors involved with this, the first of which is genetic. Some lines/hybrids tend to have ears longer than their husks will contain, at least at the tips. Some hybrids will expand ear diameter larger than husks will contain and will split open. I suspect that the protruding tips are more prominent in some hybrids than others.

Originally, in more "northern" adapted native American flint/floury maize, you tended to see this trait. I suspect that it was selected inadvertently with selection for more rapid drydown and less ear rot. Southern types of maize have quite long "silk channels," and husks that are typically two to three inches over the ear tip. I think this furnished some protection from weather and insects. In modern corn we have selected vigorously for fast drying and high yields. This has the potential for providing a long ear and short husk.

Another real impact is the environment. I suspect that the culprit this year is heat stress. At temperatures over 95°F corn respiration increases--a key factor of loss from high night temperatures. The flow of sugars to the reproductive parts--cob, kernels is prioritized over flow to vegetative parts--including leaves on the husks. Especially if pollination was solid on the ears, the fertilized ear tips continue to expand and grow. The leaf tissue on the husk may have been impacted when they weren't fed as well as usual for a week or two. This leaf tissue will never grown as rapidly again--causing the symptoms you are seeing.