Much of Indiana has experienced mild and humid weather over the past few weeks, which has influenced disease development. Gray leaf spot levels have been at low to moderate levels in most areas, but northern corn leaf blight has developed rapidly across Indiana. The high humidity and heavy dews have contributed to disease development, and in some fields the disease is at concerning levels.
Although current corn economics may make some farmers hesitant to spray fungicides, it is important to scout fields and determine if northern corn leaf blight is present in susceptible hybrids in high-risk fields for disease development, such as those that are in minimum or no-till or continuous corn. Although there are not robust thresholds in place for how much disease needs to be present to justify a fungicide application, threshold considerations and fungicide recommendations are discussed in a previous article <http://extension.entm.purdue.edu/pestcrop/2014/issue13/index.html#foliar>.
There are several races of the fungus that causes northern corn leaf blight, and race type can influence symptom expression. We have not examined what races are currently problematic in Indiana, but if you are seeing the disease in hybrids that are considered resistant to northern corn leaf blight, please let us know.
For more information on northern corn leaf blight, please read Purdue Extension bulletin BP-084-W: <http://www.extension.purdue.edu/extmedia/BP/BP-84-W.pdf>.
Northern corn leaf blight
Northern corn leaf blight has developed rapidly across Indiana. The high humidity and heavy dews have contributed to disease development, and in some fields the disease is at concerning levels. This video discusses diagnosis and management of this fungal disease.
Click on graphic to see the video.
VIDEO: Northern Corn Leaf Blight
Multiple Ears of Corn on the Same Shank – (Bob Nielsen) -
Most everyone knows that a corn plant initiates a lot of ears, one at every stalk node up to the one that becomes the harvestable one (Nielsen, 2007). Keen observers of the corn plant also recognize that multiple ears can also be found on the same ear shank. Bonnet (1966) briefly mentions this phenomenon and includes a photo in his classic publication that describes the development of inflorescences of major grass crop species. For what it is worth, I mentioned it myself fifteen years ago (Nielsen, 1999) and coined the term “MESS Syndrome” (Multiple Ears on Same Shank).
The fact that multiple ears sometimes develop from a single ear shank is not, in and of itself, physiologically unusual. Ear shank development essentially replicates the developmental pattern of the main stalk of the plant.
Fig. 1. Example of MESS syndrome
Fig. 2. Primary and secondary ear from same shank
Fig. 3. Illustration of shank nodes and internodes, plus secondary ear
Fig. 4. MESS syndrome on plant at low density
Fig. 5. MESS syndrome on plant at high density
Bonnet, O.T. 1966. Inflorescences of Maize, Wheat, Rye, Barley, and Oats: Their Initiation and Development. Univ. of Illinois, College of Ag., Agricultural Expt. Sta. Bulletin 721.
Nielsen, R.L. (Bob). 1999. What A MESS! (aka Multiple Ears on a Single Ear Shank). Corny News Network, Purdue Univ. <http://www.kingcorn.org/news/articles.99/990823b.html>. (URL accessed July 2014).
Nielsen, R.L. (Bob). 2006. A Problem with “Bouquets”. Corny News Network, Purdue Univ. <http://www.kingcorn.org/news/articles.06/Bouquets-0912.html>. (URL accessed July 2014).
Nielsen, R.L. (Bob). 2007. Ear Size Determination in Corn. Corny News Network, Purdue Univ. <http://www.kingcorn.org/news/timeless/EarSize.html>. (URL accessed July 2014).
Nielsen, R.L. (Bob). 2011. Kernel Set Scuttlebutt. Corny News Network, Purdue Univ. <http://www.kingcorn.org/news/timeless/KernelSet.html>. (URL accessed July 2014).
Cool Temperatures & Grain Yield: Déjà vu for Corn? – (Bob Nielsen)
Global warming aside, much of Indiana has experienced a cool summer to date (Fig. 1). As Yogi Berra once said, “It’s like déjà vu all over again” relative to the questions folks have been asking recently about the consequences, good or bad, of such cool temperatures on the prospects for corn grain yields at harvest this fall. Similar questions were raised only a few years ago (2009) in another recent cool growing season (Nielsen, 2009).
So............. what about the 2014 growing season and its cool temperatures? One needs to be cautious making comparisons with the 2009 growing season, especially with regard to the unpleasant harvesting experience of 2009.
Certainly, both growing seasons were cool through to about this time in July (Fig’s 1 & 2), and 2009 continued to be cool throughout much of the remaining part of that summer (Fig. 2) and into early fall. However, corn planting statewide was considerably delayed in 2009 versus the 5-year average (Fig. 3). Early season cool temperatures in 2009 sustained the delayed crop progress, resulting in about a 7-day later statewide silking period in 2009 versus the 5-year average (Fig. 4). Subsequent cool temperatures in August and September further delayed grain maturity in 2009 to nearly two weeks later than the 5-year average (Fig. 5). Coupled with poor conditions for grain drying in the field prior to harvest plus the development of ear rots and mycotoxins, grain harvest was pretty miserable for many growers in 2009. Nevertheless, estimated statewide grain yield in Indiana for 2009 set a new state record at 171 bu/ac that was not exceeded until last year’s record yield of 177 bu/ac (USDA-NASS, 2014b).
Fig. 1. Daily rainfall and max/min air temperatures for June and July, 2014 in westcentral Indiana. Source of graph: Midwest Regional Climate Center.
Fig. 2. Daily rainfall and max/min air temperatures for June through August, 2009 in westcentral Indiana. Source of graph: Midwest Regional Climate Center.
Fig. 3. Planting progress of corn in Indiana for 2014 and select years. Data: USDA-NASS
Fig. 4. Silking progress of corn in Indiana for 2014 (as of 7/20) and select years. Data: USDA-NASS. Data: USDA-NASS
Fig. 5. Grain maturity progress of corn in Idnaian for select years. Data: USDA-NASS