With the water receding and fields slowly
drying off, many wheat and barley fields have a yellow/light
green hue and don’t look all that healthy. The first couple
of leaves are dying off and the new growth doesn't look
all that healthy either. This is especially true for lower
laying parts of the fields. Will this crop survive and what
causes this yellow/light green tint?
Other than wild rice, wheat and barley probably tolerate flooding
and water logged soils the best of any of the crops grown in
this region. Barley is a bit more sensitive than wheat, but
under the conditions that we experienced last week, both should
be able to handle 3 to 4 days of flooding/saturated soils without
too many problems. What are the possible causes for the unhealthy
color of many wheat and barley fields?
- Acute nitrogen deficiency due to denitrification -
in soils that are waterlogged, bacteria will cause
denitrification by converting nitrate nitrogen into nitrogen
gases. This in turn, will result in a nitrogen deficiency
of the crop. The first visible symptoms are a dying off
of old leaves and/or a pale green color as the crop recycles
the nitrogen available in the plant from the old growth
into the growth.
- An outbreak of tan spot, spot blotch, and/or net blotch
- tan spot of wheat, and spot and net blotch in barley
are residue born diseases caused by different Helminthosporium species. Like
all fungal diseases, these leaf diseases need water
to develop and the torrential rains of the 9th have
provided that moisture. The North Dakota State University
(NDSU) disease forecasting system indicates that for
most locations in the Red River Valley, conditions for
tan spot infections have been favorable for 4 to 7 days
in the last 7 days. Early symptoms of an infection are
small chocolate colored round to oblong lesions. Wheat
and barley that are nitrogen deficient are also more
susceptible to tan spot, spot blotch and net blotch.
The incidence and severity of the diseases should be
highest in fields that had wheat or barley as previous
crop.
So can this crop be helped? Well, first it is important
to access whether the crown and crown roots of the wheat
and barley plants are healthy and growing. The simplest thing
to do is to dig up plants from affected areas, wash off the
soil with water, and inspect the tissues. Healthy plants
have white crowns and crown roots. Cut the crown lengthwise
in half to see whether there is any brown discoloration inside
the crown tissue. Brown discoloration of crown tissue may
be a sign of root rots. The nitrogen deficiency should alleviate itself in a week
to ten days as the crops resume growth and find additional
nitrogen in the soil profile. If the color doesn’t return
in a week, supplemental nitrogen may be needed. The best
method to determine the nitrogen status of the crop is to
send in a plant sample for analysis. To control the early
outbreak of tan spot, a 2 fluid ounce application of Tilt
is recommended. This application can be combined with most
herbicides labeled on small grains, but always check and
follows label directions. |
