By Peter Thomison, Ohio State University Extension
In the July 23, 2010 issue of the Illinois Pest Management Bulletin, Dr. Emerson Nafziger describes an unusual phenomenon “in which corn kernels seem to start to develop after pollination but are empty of content.” Affected kernels appeared to contain only clear liquid with perhaps a small amount of white material–probably starch–that may later turn yellow.” An image of a corn ear showing the symptoms is included with the article athttp://bulletin.ipm.illinois.edu/article.php?id=1387. The liquid in these “bubbles” eventually dries up, leaving what are essentially seed coats without an embryo or endosperm. These may flatten as kernels on both sides press in during grainfill, if there are only a few, scattered “bubble kernels” on an ear. Dr. Nafziger notes that corn ears exhibiting “bubble kernel” symptoms were associated with late glyphosate application and observes that conditions after application this year might have favored the development of the effect.
In recent years, there have been reports that pretassel applications of various pesticides and surfactants, especially non-ionic surfactants, may result in arrested ear development and poor kernel set (http://corn.osu.edu/newsletters/2009/article?issueid=282&articleid=1680). In a 2009 Ohio FSR evaluation conducted by ag educators Harold Watters and Jonah Johnson, ears with “jumbled” kernels resulted from applications of herbicides and various adjuvants at early tassel. Kernel jumbling was particularly severe in the glyphosate+AMS+NIS treatment. Shriveled, aborted kernels scattered throughout ears promoted the jumbled kernel appearance.
The “bubble kernels” remind me of another kernel development problem reported by Dr. Bob Nielsen at Purdue University several years ago, which he characterized as “translucent kernel syndrome” (http://www.agry.purdue.edu/ext/corn/news/articles.99/990903.html). According to Dr. Nielsen, “the initial symptoms of this oddity were the appearance of plump, translucent, liquid-filled kernels scattered randomly among already-dented kernels throughout an otherwise normal-looking ear.” The abnormal kernels subsequently shriveled as the kernels matured, “resulting in a shriveled kernel appearance not unlike mature sweet corn kernels.” Dr. Nielsen also did not specify a cause suggesting several possibilities from high temperatures to a possible genetic factor. However, glyphosate was not mentioned; the report pre-dated widespread use of glyphosate resistant hybrids and suggests that “bubble”- “translucent” kernel symptoms may occur as the result of several factors.