SA Graan Augustus 2015

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Augustus 2015
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Arrested ear syndrome rears
its head in South Africa
Arrested ear syndrome, also called blunt ear syndrome, a
relatively unknown phenomenon in South African maize
production, has appeared in isolated areas this past
season. Some producers have realised only half of their
yield expectation in certain fields due to high incidences of arrested
ear syndrome.
While largely unreported in South Africa, this phenomenon has
been reported sporadically in the USA corn-belt since the late
1990s. Arrested ear syndrome is not caused by a pest or disease.
It is linked rather to plant stresses at a sensitive stage of ear
development causing partial or complete abortion of the ear.
This occurs during the late vegetative growth stages of the maize
plant. See Photo 1a to 1d.
In all other aspects, the maize plant with an arrested ear appears
normal. As the season progresses, stems and leaves of plants
with severe ear arrest will often colour red or purple due to sugar
deposition in these organs. The stunting or absence of the ear
has a direct impact on the yield potential of the affected land. In
lands with a high percentage of arrested ears, one would expect
the yield loss to be in a similar proportion to that of the arrested
ear syndrome.
One of the most common theories proposed to explain arrested
ear syndrome in the USA is cold stress. In particular when
associated with a sudden drop in average temperature. Due to
the unpredictability of arrested ear syndrome the exact cause
and timing of the stress event that results in ear arrest has been
difficult to determine or replicate, despite various studies that have
been undertaken.
In 2007 numerous reports of arrested ear syndrome emanated
from the Midwestern corn-belt in the USA. Researchers from
Purdue University investigating some of these incidences noted
that a common thread linked many of the reported cases. In nearly
all of these cases of arrested ear syndrome a pre-tassel applica-
tion of crop protection chemicals, often including adjuvants, had
been applied.
In 2008 these researchers designed some demonstration plots
to test if these sprays could have increased the incidence of arrest-
ed ear syndrome. In their demonstration they included three fungi-
cides sprayed alone and in various combinations with insecticides,
adjuvants, spray additives and herbicides. The different treatments
were then assessed for arrested ear syndrome and compared to an
unsprayed control block.
From Graph 1 it would appear that the more components that are
added to the spray mix, the higher the rate of arrested ear syn-
drome. Fungicides alone or fungicides plus an insecticide were no
different to the unsprayed control from an arrested ear perspective.
Arrested ear syndrome appears to be linked to the presence
of non-ionic surfactants (NIS) and crop oil concentrate (COC),
both of which are common ingredients in adjuvants, and also linked
to multi-chemical tank mixes.
ON FARM LEVEL Arrested ear syndrome / Plant stresses Integrated pest control
GRANT PRINGLE, agronomist: Pannar
Graph 1: Graphical representation of arrested ear syndrome as a percentage resulting from various crop protection chemical sprays applied at the V14
growth stage on maize.
I = insecticide; COC = crop oil concentrate; NIS = non-ionic surfactant; GLY = glyphosate; AMS = amonium sulphate
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