Farm Horizons
•
Aug. 8, 2016
•
Page 11
August is prime time for field scouting
August and September are my favorite
tinuous corn fields that are irrigated.
months for scouting corn fields. By this
The other disease to watch for is northDave Schwartz ern corn leaf blight. Its cigar-shaped letime, we have an idea of what to expect
Certified crop advisor
for corn yield. When I scout, I look for
sions are quite easy to identify.
Gold Country Seed
insect and disease pressure, nutrient deWhen diseases build up in a field, it’s
ficiencies, and differences between corn
a good idea to rotate out of that crop for
hybrids.
a few years.
The main nutrient deficiency I see in
Insects
August
is
nitrogen.
I’m afraid this will be an issue in too
The major corn insect I scout for is corn rootworm.
many
fi
elds
this
year,
because of the saturated soil growThe northern corn rootworm (green beetle) is normally
ers
had
to
deal
with
back
in May and June. Lower leaves
what we find in our area, unless the field has been conon
the
plant
turn
yellow
beginning
at the leaf tip and then
tinuous corn.
down
the
midrib.
Nutrient
defi
ciency
appearing in AuWestern corn rootworm (beetle with black stripes on
gust
can
take
away
20
to
40
bushels
per
acre.
back) is pretty much limited to fields in continuous corn.
These rootworms do not overwinter in our area, as well Corn hybrids
as northern corn rootworm.
The third item I scout is the corn hybrid itself. How
Corn fields most at risk of corn rootworm are those that well does the hybrid withstand moisture stress? Does the
are in a continuous corn rotation and those planted very husk hold tight to the ear and stay in an upright position,
late in the season. Beetles will migrate into late planted or does the husk open up and ear hang down, allowing
fields, feed on silks and pollen, and then lay their eggs. If grain to dry down? What is the general health of the plant
high numbers of corn rootworm beetles are found, fields in September? Are hybrids maturing on schedule?
will either need to be rotated out of corn the following year
I have discovered that there is no perfect hybrid. This
or managed with a hybrid with a corn rootworm trait.
is why it’s important to scout fields now, and then select
hybrids that best match the needs of individual fields. n
Diseases
From a disease standpoint, there are several diseases
to scout. Stalk rot may be the most common disease that
seems to show up somewhere, nearly every year.
Identifying stalk rot early in the fall is important so
growers know what fields to harvest first. This is done by
simply walking down the field and pushing stalks to the
side. Healthy stalks will spring back to an upright position. Plants infected with stalk rot will stay bent over.
Irrigated fields normally have more disease pressure,
because more corn is typically grown on this land and the
environment is wetter than dryland corn.
Goss’s Wilt is a disease that was identified a few years
ago in western Minnesota. It can now be found all the
way up into the Red River Valley. Goss’s Wilt needs a
continuous corn rotation because it’s a bacterial disease
and doesn’t overwinter well. It can be found in many con-
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