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his article is admittedly fearmongering on the part of
your friendly neighborhood corn specialist, but I figure it is my prerogative
and responsibility to do so when I believe conditions are ripe for the
development of a potential crop problem. If the problem does not occur, then
growers will be relieved and they will forget I said anything about it. If the
problem does occur, then I will look pretty smart for having forecast its
development.
The potential problem of which I speak is a phenomenon
traditionally called 'silk balling'. I prefer the name 'scrambled silks'
because I think it is more descriptive. The problem is one in which silk
elongation, prior to their emergence from the husk leaves, is interrupted or
altered, resulting in a mass of scrambled silks near the tip of the cob that
never fully emerge from the husk. Obviously, any silks that fail to emerge from
the husk will not exposed to any pollen and consequently will not contribute to
the formation of kernels on the cob. The net result is some degree of
barrenness on the cob and, consequently, lower yield.
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Gallery ]Scrambled silks is a relatively infrequent problem and its causes are not well understood. Some believe that the occurrence of cool nights (low 60's or cooler) prior to silk emergence plays a role in the development of scrambled silks. Others believe that rapid changes in temperature patterns (e.g., very warm to very cool) prior to silk emergence encourages the problem. Hybrids with naturally tighter husks seem to be more susceptible to developing scrambled silks.
Given these opinions on temperature factors that may contribute to the problem, one could speculate (some would say fearmonger) that recent unusually cool nights throughout the central and northern parts of Indiana, plus the current forecast for more of the same, may lead to an increased occurrence of scrambled silks this year.
Unfortunately, there is nothing you can do about preventing or
avoiding the problem. Nonetheless, it would be prudent to walk some of your
fields during or after pollination and look for evidence of the problem.
Typically, the severity of the resulting poor kernel set is low and
concentrated near the tip end of the cob. However, I've seen situations in the
past where scrambled silks resulted in severe barrenness in nearly 1/3 of the
plants in a field.
If you don't have time to walk your fields right now, any affected plants will likely raise red flags later on in the grain filling process. By this, I mean that any plants severely afflicted with barrenness will eventually develop purpling or reddening of leaf midribs, leaf sheaths and other plant parts.
The reasons for this discoloration are similar to those for
purple corn earlier in the growing season. An otherwise healthy plant whose ear
is highly barren of kernels is a plant that is overproducing photosynthate
(source) relative to the demands of existing kernels (sink). The excess sugars
in the leaves and stalk trigger the formation of anthocyanin pigments in the
plant tissues, especially in those hybrids with quite a few of the purpling
genes. The similarity to early season purple corn is in the connection between
excess plant sugars and anthocyanin production. Early in the season, excess
plant sugars often result when root development is hindered for some reason.
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For other information about corn, take a
look at the Corn Growers Guidebook on the World Wide Web at
http://www.kingcorn.org