A Problem With "Bouquets"

URL: http://www.kingcorn.org/news/articles.06/Bouquets-0912.html

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address:

n unusual oddity of corn growth and development has been reported in scattered fields throughout at least Indiana, Illinois, and Iowa in recent weeks.Years ago, I labeled this oddity a MESS (aka Multiple Ears on Same Shank) that was usually found only in the occasional corn plant along the edges of a field (Nielsen, 1999). This year, the oddity can be more accurately characterized as a problem because of the high percentages of plants affected in some fields.

Multiple ears on a single plant are not unusual, but the multiple ears usually develop separately from individual stalk nodes (Image 1). The oddity/problem being reported this season is one of multiple ears that originate from individual nodes on a single ear shank (Images 2, 6).

First Comment: The fact that multiple ears can develop from a single ear shank in and of itself is not unusual. The ear shank is essentially a replica of the main stalk of the plant. The ear shank develops leaves like the main stalk. These husk leaves originate from individual nodes of the shank like the main leaves develop from individual stalk nodes. The ear shank terminates with a reproductive organ (the female ear) somewhat akin to the main stalk terminating with a reproductive organ (the male tassel). Additional ear shoots can develop from individual nodes of the ear shank (Image 4) like additional ear shoots that develop from individual nodes of the main stalk (Image 1).

Second Comment: Normally the ear shank does not initiate these secondary ears or ears initiate but eventually cease development likely due to apical dominance from the apical ear (Image 5).

Third Comment: What is unusual this year is the occurrence of a "bouquet" effect of 3 to 5 ears or more developing from an individual ear shank (Image 6). Furthermore, and particularly disconcerting to growers, in many cases none of the multiple ears successfully pollinate and set kernels. In some cases, all of the multiple cobs are severely stunted as well. Where kernel set is nonexistent or very limited, the affected plants eventually turn red/purple in response to excessive photosynthate concentration in the leaves and stalk tissues. In some situations, as much as 30 to 50% of the plants in an area of a field are affected. Obviously, the yield loss in these severe situations will be dramatic.

Fourth Comment: The cause of this "bouquet" effect of multiple ears is not known. Some of us have been trying to compile background information from affected fields, but the number of affected fields has admittedly (and thankfully) been few. To my knowledge, there has yet been no single common thread identified among the affected fields. What I suspect is that a) some hybrids are genetically prone to developing multiple ears on a single ear shank and b) more than one external "trigger" enables the development of multiple ears to occur on these hybrids. Identifying the "trigger(s)" is the challenge.

For example, the "bouquet" effect is showing up in one of three hybrids I am using this year in my planting date demo plots at the Crop Diagnostic Training Center near West Lafayette (i.e., a hybrid apparently prone to multiple ears). Furthermore, the "bouquet" effect is more prevalent and severe in later planted plots where silk clipping by rootworm beetles prevented kernel set on the primary ear (i.e., possibly minimizing or negating apical dominance against secondary ears).

Final Comment: If you find this problem in your field, please contact me (rnielsen@purdue.edu) and share the relevant background information of the field with me.

Click on image to open a larger version. To close popup window, click on larger image.

1. Multiple ears on single plant, but originating at different stalk nodes. This type of multiple ear development is not uncommon, though usually restricted to two or three nodes.	2. Multiple ears on single plant, but two originating from same stalk node. This type of multiple ear development is not as common.
3. Closer view of double ear at same ear shank. Second ear attached at lower shank node.	4. Even closer view of double ear at same ear shank. Second ear attached at lower shank node.
5. Double ear originating from same ear shank, but second ear withered away as usually occurs.	6. A "bouquet" of 5 ears originating from the same ear shank.
7. Two "bouquets" of multiple ears originating from two nodes of the main stalk.	8. Closer view of a "bouquet" of 4 ears originating from same ear shank.
9. Even closer view of a "bouquet" of 4 ears originating from the same ear shank.	10. Husks removed from "bouquet" revealing barren cobs, the upper two of which resulted from persistent silk clipping by rootworm beetles.
11. Leaf reddening in response to photosynthate buildup resulting from absence of kernels on ears of "bouquet".	12. A "bouquet" of 3 ears originating from the same ear shank.

Related References

Nielsen, R.L. (Bob). 1999. What A MESS! Corny News Network, Purdue Univ. Online at http://www.agry.purdue.edu/ext/corn/news/articles.99/990823b.html [URL verified 12 Sep 2006].

For other Corny News Network articles, browse through the CNN Archives at http://www.kingcorn.org/news/archive.html.

For other information about corn, take a look at the Corn Growers' Guidebook at http://www.kingcorn.org.

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