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Green
Snap in Corn Caused by Several Factors
Green snap (sometimes called
brittle snap) is a phenomenon seen commonly throughout the Midwest. While
it can occur anywhere corn is grown, it is most often associated with
strong thunderstorm winds which are more frequent in this geography. These
straight line winds and " down bursts" associated with thunderstorms
are one of the biggest factors contributing to green snap.
Breakage occurs at the nodes
of the stalks. This is the area where stalk growth originates. This rapidly
elongating tissue becomes brittle and is prone to breakage.
There are many factors involved
in the occurrence of green snap. They include stage of growth, timing
of thunderstorms and high winds, growing conditions, growth regulator
herbicides and hybrid sensitivity.
Here's more detail about each
of those factors:
Stage of Growth
-- Corn undergoes two particularly rapid growth periods. The first
occurs from V5 through V8. At V5 the plant is 8 to 10 inches tall. During
that time, the growing point emerges from below ground. Nodal roots begin
to elongate and rapid growth of leaf and stalk tissue follows. This rapid
growth causes the elongating cells in the internodes to become quite brittle.
Unfortunately, conditions favorable
for growth, such as warm temperatures and abundant moisture and fertility,
increase potential for breakage. If high winds occur at this stage, losses
can be significant. Breakage at this point occurs at or just below the
soil surface.
Tillers may grow from lateral
growing points but likely will contribute little or nothing to yield because
they rarely set harvestable grain.
The second period of rapid
growth occurs at V12 to tasseling. At the V12 stage corn is approximately
3 to 4 feet tall. This, in fact, is the most rapid growth period. At this
stage the plant will grow an additional 4 to 6 feet in the neighborhood
of 3 weeks.
Again, high winds offer the
potential for loss. Not only is the plant vulnerable because of it’s
growth stage, but also it’s size and increased resistance to the
wind enhance the problem. Breakage generally occurs at a node just above
or below the ear. That severely limits grain development on affected plants
because of the greatly reduced leaf surface which is the source of photosynthate
for grain development.
As plants reach full height,
the risk of green snap greatly diminishes because the plant lays down
structural material to support the mature plant.
Growth Regulator Herbicides
Can Affect Corn
Growth regulator herbicides
(2,4-D, Banvel, Clarity and other phenoxy compounds) have been used effectively
for many years as a cost effective means of controlling troublesome weeds.
Unfortunately, as the name implies, they cause abnormal cell enlargement
in meristematic regions of the plant, including corn node regions. In
addition, the application of these herbicides coincides closely a stage
when corn is most vulnerable to breakage. Take extreme care to follow
label recommendations for application rate and corn size. In addition,
certain additives used with tank mixes increase the uptake of herbicides
in the plant. It is particularly important to watch the weather conditions
at time of application to avoid enhancing the potential negative effects.
Management Summary
Plant at proper depth: Planting
depth may have a direct bearing on breakage. Shallow planting can restrict
corn nodal root development. Most growth regulator herbicides are quite
water soluble and can easily be moved into this zone. From here they are
easily taken up by the plant and translocated to critical growing points
of the plant. Always maintain a one and three-fourths to two inch planting
depth.
Manage Herbicides: Always
follow label directions. Pay particular attention to rates as they relate
to plant height or stage of development. Use additives only when called
for, and at proper rates. Be sure to delay drop nozzle applications of
2,4-D until after corn plants have reached the brown silk stage.
Hybrid selection: To
reduce risk, planting an array of hybrids that span your adapted maturity
range. That will reduce specific hybrid interactions plus, a maturity
range should mean that not all plants in all fields will reach the vulnerable
stage at the same time.
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