| |
White Heads In Wheat
5/26/2005
Ron F. Meyer
Area Extension Agent
(Agronomy)
Colorado State University Extension
Golden Plains
Area |
 |
| I have provided this information to assist you
with making informed decisions. If you have questions about this article or
suggestions on making this or other articles better, please click on the
buttons below. |
|
|
|
As area wheat crops are now headed, white heads in many fields are
becoming obvious. There are a number of causes for white heads, which are
explained below.
Frost injury: Frost during the late
joint to early boot stage can cause partial white heads. The damage can
occur at the bottom of the head. The unaffected portion can fill grain
normally. Freeze-damaged heads may be completely or only partially
white. They are often deformed in the freeze occurred in the late boot
stage. White heads caused by a late freeze may be uniformly spread
throughout the field or may occur mostly in low-lying areas of the field.
Freeze damage will reduce yields and test weights.
Dryland root
rot: Dryland root rot is found most commonly in Oklahoma and
southern Kansas. The disease usually causes all the tillers on an
infected plant to turn prematurely white. The field pattern can be single
affected plants or patches of affected plants that tend to be in the drier
areas of the field. Dryland root rot occurs most often under drought and
stress conditions. It can easily be confused with take-all, since both
diseases cause all the tillers on the plant to die prematurely and turn heads
white . . . Dryland root rot attacks the crown and lower stem. It causes
the lower 2-3 internodes to turn brown or pink. Plants do not pull out of
the ground easily as with take-all. Both diseases are encouraged by
continuous cropping of wheat. It is probably not necessary to manage
specifically for this disease since general good management practices (moisture
conservation, rotation) also help control it.
Take-all root
rot: Take-all results in large patches of wheat with heads that
turn prematurely and completely white, in a pattern that is very similar to
dryland root rot. However, take-all is favored by high moisture rather
than drought conditions. This root disease will cause stunting.
Wheat infected by the take-all fungus will look ragged, tiller poorly, and have
small white heads. Infection usually begins as the wheat begins to tiller
in the spring. Take-all often causes the base of the stem to turn a shiny
black. Stems do not break over at the base, but the plants can easily be
pulled up out of the ground because the roots are rotted. Yield losses
are essentially total in patches affected by take-all. It is usually
worse at a soil pH of 6.0 or above, and in continuous wheat.
Stem
maggot: When white heads appear on only a very few isolated
plants soon after heading, the cause is likely wheat stem maggot. Heads
and the portion of stem directly below the head are completely white.
However, the leaf sheath and lower stem are green. Heads can easily be
pulled from the stem due to chewing injury from the maggots. Overall,
field yields and test weights are not likely to be affected.
Hail
damage: Hail may cause breakage of spikelets or the whole
head. If it strikes early, white heads or partial white heads may
result.
Heat and drought stress: When it gets
extremely hot, patches of wheat can die suddenly and turn white. Affected
wheat is often on the upwind side of a field. Drought can also cause
premature death of plants which, results in white heads. The pattern will
follow the drier areas of the field. Drought can be difficult to
distinguish from dryland root rot. The difference is that
drought-affected plants have normal crowns.
Source: Steve
Watson, Lone Tree Publishing |
Page Created and Maintained by: Perry D. Brewer, Area
Extension Agent (Technology Education/Youth)
6/1/2005 |
|
|
Colorado
State University, U.S. Department of Agriculture, Kit Carson, Phillips,
Washington and Yuma counties cooperating. Extension programs are
available to all without discrimination. Where trade names are used, no
discrimination is intended and no endorsement by Colorado State University
Extension is implied. |
