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integrated management strategies are the best way to prevent in-
fection of the crops. Each control strategy has a level of effective-
ness towards the control of
Fusarium graminearum
species complex
infection (
Table 5
).
Highly effective control strategies
Crop rotation
Fields that are grown in monoculture or rotated with similar crops
result in crop residue from host plants, enabling the pathogens to
overwinter on their crop of choice.
Crop residue management
Crop residue from the previous seasons will serve as the primary
inoculum source for new infection in the growing season. In order
to lessen disease, the residue can be physically removed, tilled
into the field or be treated with microbial agents that aid in decom-
position.
Harvest time and storage
Late harvest poses a high risk and it is therefore important to
choose cultivars that are adapted to local climatic conditions. Mois-
ture should be restricted to a minimum during storage, so grain can
be dried to less than 15 %. Good storage practices such as appro-
priate temperature and moisture content, as well as insect control,
aeration and clean bins should be maintained.
Insect control
Both the maize stalk borer (
Busseola fusca
) and spotted stalk
borer (
Chilo partellus
) are linked to an increase in
Fusarium
spp. in-
fection as the feeding wounds create openings for the pathogens.
Medium effective control strategies
Good nutrient supply
High levels of nitrogen and low levels of potassium can predis-
pose the maize plant to
Fusarium graminearum
species complex
infection.
Varietal choice
There seems to be two types of hybrids that are more susceptible
to Fusarium and Gibberella ear rot, namely those cultivars with
vertical ears that have poor ear cover and those with tight ear
husks, respectively.
Low effective control strategies
Seed quality
Although seed quality has a minimal effect on
Fusarium gramine-
arum
species complex infection, it should be of the best quality
and free of disease.
Sowing time
Early planting usually escapes the worst infection.
Crop structure
High plant density favours disease development.
Weed control
Although weeds have a low effect on
Fusarium graminearum
species complex disease development, it may serve as an indirect
control measure by increasing the humidity in the field.
Chemical disease control
Chemical control can be applied when
Fusarium
spp. systemical-
ly infects the maize plant early in the season. However, this does
not work later in the season. Presently, there is no fungicide known
to control
Fusarium graminearum
species complex.
Future research
Present research is performed in collaboration with researchers
at Stellenbosch University in order to better understand the
disease complex. The factors that are investigated include inocu-
lum build-up (of the fungal isolates), pathogenicity of the
Fusar-
ium graminearum
species complexes, epidemiology of species in
the specific plant tissues, as well as development of management
strategies.
3: The
Fusarium graminearum
species complex-infected wheat grain has a pink-red colour and is
dwarfed in comparison to the healthy wheat grain.
Photo: Gert van Coller
4: Visible fungal growth observed on infected sorghum grain.
Photo: Neal McLaren
Gibberella on maize,
sorghum and wheat
3
4