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outomatiese strookwydte beheer
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GPS LEIDING: KIES TUSSEN TWEE
GEBRUIKERSVRIENDELIKE OPSIES
E
R
V
to shift to management strategies in the field
to ensure the quality and safety of maize food
and products.
This is complicated by the complexity of
interactions between numerous abiotic and
biotic factors, our need to understand them,
and their manipulation to prevent or reduce
the growth of
F. verticillioides
and thereby
reducing contamination by fumonisins.
To date, no fungicides have been registered for
the control of ear rots in South Africa and the
efficacy of available chemicals still needs to be
determined. Feeding activities of lepidopterous
insects may spread
F. verticillioides
spores to
silks, kernels, stems and feeding channels,
increasing colonisation by the fungus.
Bt-transformed maize contains genes from
Bacillus thuringiensis
encoding for insecticidal
crystal proteins. Reduced insect damage
on Bt maize stalks can reduce infection by
Fusarium
spp. through plant injuries and
reduce fumonisin levels as a result. Birds
that cause physical injury to stalks and ears
are also suspected to promote infection by
Fusarium
spp.
The most plausible solution seems to be
prevention in the field through crop techniques
that are able to guarantee less favourable
conditions for
F. verticillioides
development and
subsequent fumonisin production. Cropping
practices such as N fertilisation, timing of
sowing and harvesting, insect control and plant
density influence fumonisin contamination in
maize grains. Preliminary studies carried out in
a field trial by the ARC-GCI, during the 2011/2012
planting season, indicated that higher plant
populations had no effect on fungal infection,
but an increase in fumonisins was observed.
This observation must be confirmed with
another two season’s data.
These significant higher fumonisin levels
observed at higher plant densities could be
attributed to “stress” factors on the plants
caused by competition for water and nutrients.
It has been indicated in literature that low
temperature and water stress reduce fungal
growth of
F. verticillioides
, but an increase in
water stress increased
FUM 1
expression which
is the first step in fumonisin synthesis. This
could possibly explain higher fumonisin levels in
the presence of higher plant densities although
fungal biomass was not significantly increased.
It is evident from literature and this study that
maize cultivated at high plant populations, may
exhibit a significant increase in fumonisin risk
in maize grain. The correct plant population in
different maize production areas will depend
on local climatic conditions, soil fertility, crop
techniques and the genotype used. Maize
producers are therefore encouraged to enquire
about optimum plant populations suited to
their area and production practices, as this
could be critical in reducing fumonisins in the
maize crop.
Photo 3: White cottony-growth of
F. verticillioides
on maize kernels.
