and plants exhibiting stunted
growth (dwarfing). Internal infection of these plant parts is characterised by pink to red discolouration
of the tissue (Figure 2) and severe
infection will result in the lodging
of plants.
FHB of wheat has been found in the
wheat-producing areas of South
Africa. The first symptoms of FHB
occur shortly after flowering and is
characterised by bleaching of the
diseased wheat spikelets (Figure 3).
Infection of the developing grain by
the fungus causes it to shrink and
wrinkle (known as “tombstone”
grain) with a pink-light brown discolouration. Infection is prevalent
when warmer and wet conditions
concur with wheat flowering and
early grain fill.
Disease symptoms associated with
GM of sorghum are pink, grey,
white or black discolouration of the
grain surface, reduced grain size
and/or dry matter accumulation or
the complete destruction of the
grain itself (Figure 4). The presence
of the disease is also characterised
by stalk rot symptoms with tan or
pink-to-purple internal discoloration.
Effects of mycotoxins produced
by FGSC
The mycotoxins produced by FGSC
species have been associated with a
number of health implications in
humans and domestic animals. The
ingestion of DON-contaminated
food in humans has been associated with nausea, vomiting, diarrhoea
and acute gastrointestinal illness. In
animals, DON-contaminated feed
can lead to food refusal, vomiting,
decreased weight gain and less effective feed utilization. Interestingly, ruminants and poultry seem to
be resistant to DON. The more toxic
mycotoxin, NIV, has also been
found in wheat and maize in South
Africa but at a lower frequency
when compared to DON
(www.sagl.co.za). The mycotoxin
ZEA has been linked to hypoestrogenic syndromes in humans
and has been implicated as a potential stimulator of human breast
cancer cells. ZEA has also been detected in beers from Lesotho and
Swaziland. In farm animals, ZEA
may cause reproductive disorders,
particularly in pigs, and may result
in reduced egg-production in poultry.
Management of FGSCassociated diseases
Diseases caused by species of the
FGSC should be managed from the
farm and throughout the postharvest management chain. The
following recommendations may be
employed:
Removal or burial of plant material after harvest will remove the
primary source of moulds for the
following growing season although this may conflict with soil
conservation practises
Crop rotation with legumes, cotton, brassicas, sunflower or potato would help reduce the inoculum present in the soil
Planting at recommended plant
densities, proper fertilisation and
irrigation practices would result
in healthy/strong plants and reduce the potential for disease
development
Effective application of insecticides to limit the population of
insects which could damage
Figure 3. Wheat heads displaying typical Fusarium head blight (FHB) symptoms characterised by premature bleaching of the wheat heads in the field .
Photo by I. Beukes