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T
HIS TIME OF THE YEAR THE MOST MAIZE PRO-
DUCTION INPUTS SHOULD HAVE BEEN DONE
IN THE EASTERN PARTS OF THE COUNTRY. THE
HERBICIDE APPLICATION AND TOP DRESS CAN
STILL BE DONE IN THE CENTRAL PRODUCTION
AREAS LIKE THE FREE STATE AND NORTH WEST. IT IS
ALSO IMPORTANT TO BE ON THE LOOKOUT FOR MAIZE
STEM BORERS.
There are different pests in this category so contact your representa-
tive to make sure that the correct chemicals are correctly applied.
To ask for help is not a sign of weakness but of strength. This is
also applicable for maize leave diseases. The incorrect application of
chemicals will not control the disease, yield losses will occur and the
chemicals still need to be paid. Double whip beating.
Grey leaf spot, bacterial streak and sunburn damage are some-
times confused by the untrained eye. Management of these prob-
lems is very different, and in some cases not even possible. Pannar
Seed’s free smartphone app,
Sprout
is a good source of information.
It summarises and provides a brief description of the most important
diseases found on maize in South Africa. This enables the farmer in
conjunction with his local agriculturist or chemical representative to
manage the relevant disease correctly.
Before they occur, the most important maize leaf diseases have
unique needs in terms of environmental conditions. Furthermore,
the physiological growth stage of the plant determines when certain
diseases appear.
The most important maize leaf diseases for which the farmer
should be on the lookout are combined in
Table 1
.
NORTHERN CORN LEAF BLIGHT
The most common leaf disease that occurs in most of the maize-
producing areas of South Africa is northern corn leaf blight (white
rust)
Photo 1
. Environmental conditions that promote the disease
are moderate temperatures (18°C - 27°C), moist conditions and long
dew periods. The fungus survives on maize leaf residues, and multi-
ple secondary infections develop throughout the season from exist-
ing lesions.
The lesions are usually noticed on the bottom leaves first, and as
spores are released under favourable conditions from these lesions,
the upper leaves are infected and it seems like the disease creeps up
the plant.
COMMON RUST
Common rust (
Photo 2
) is usually noticed for the first time during
the season on the young maize plants. Environmental conditions
that promote the disease are moderate temperatures (16°C - 25°C)
and moist conditions (>95% humidity). Common rust infection is
promoted by dew/fog conditions – especially during the night when
spores on the leaf surface germinate and penetrate the leaf through
the stomata.
Early signs of rust infection are visible approximately five days
after initial infection as small flecks on the leaves, and proper rust
pimples (ten to 14 days) (Photo 2) then develop and release spores.
On release these spores can be distributed across great distances by
the wind. These spores can even infect the same plant again within
the same season.
GREY LEAF SPOT
Another important maize leaf disease is grey leaf spot (
Photo 3
).
Environmental conditions that promote the disease are moderate to
high temperatures and high humidity (>95%).
Be on the
l
oo
kout
for
LEAF DISEASES
on maize
Pietman Botha, Pula Imvula
contributor. Send an email to
pietmanbotha@gmail.com
Northern corn leaf blight.
1
Common rust.
2
MADE POSSIBLE BY
THE MAIZE TRUST
6