83
September 2014
FOCUS
Integratedpest control
Special
Integratedmanagement of
Busseola
fusca
,
Fusariumear rot and
fumonisins inmaize
F
usarium ear rot of maize (
Photo 1
and
Photo 2
) is caused by
Fusarium verticillioides
,
F. subglutinans
and
F. proliferatum
.
Fusarium ear rot reduces maize grain quality (Photo 1 and
Photo 2).
Fusarium verticillioides
and
F. subglutinans
are found
in maize in all maize producing regions in South Africa, however
F. proliferatum
is the least frequently isolated species in maize in
South Africa.
Fusarium verticillioides
can survive within the maize
plant without showing visible symptoms.
Fusarium ear rot epidemiology
Fusarium species, particularly
F. verticillioides
, survive in maize
stalks as thickened hyphae. The soil borne hyphae germinate
and infect the germinating seed and roots and move up the plant
through systemic growth. The fungus also produces airborne spores
that canspreadwithin the fieldand infectmaizeears through thesilks.
Fusarium verticillioides
infects maize kernels through systemic in-
fections from contaminated seed aswell as through the silk channel
by airborne spores. Silk colonisation by
F. verticillioides
starts from
the tip of the ear downward. Infection increases if there is late-sea-
son rainfall and is also affectedby thephysiological stateof the silks
after pollination.
Direct infection of kernels can also occur throughweak points such
as stress cracks in the pericarp. The fungus is released back to the
soil through infected stalks or infected seed.
Fumonisins
The most detrimental effect of
F. verticillioides
is its production of
mycotoxins called fumonisins. Fumonisins can cause human di-
seases such as neural tube defects and have been associated with
oesophageal cancer.
Various diseases, such as pulmonary edema in pigs, can occur as a
result of ingestion of fumonisin contaminated feed. Pulmonary
edema is the accumulationof fluid in the air spaces of the lungs and
it leads to impairedgas exchange andmay cause respiratory failure.
Toxicity to chickens and broiler chicks can also occur as a result of
consumptionof fumonisin contaminated feed.
Liver cancer in rats has also been recorded due to ingestion of fu-
monisin contaminated feed. Themost dramatic effect ofmaize feed
contaminated with fumonisin, is equine leukoencephalomalacia
(ELEM), a neurotoxindiseaseof horses, donkeys and rabbits.
The symptoms of the disease are apathy, drowsy appearance with
protruding tongue, reluctance tomove backwards, aimless circling,
anda lackofmuscleco-ordination.Horsesare themost sensitivean-
imals to fumonisin toxicity, death typicallyoccurswithina fewhours
tooneweek of fumonisin contaminateddiet consumption.
Busseola fusca
damage inmaize
Busseola fusca
moths (
Photo 3
) mostly lay their eggs behindmaize
leaf sheaths before tasselling and they only lay eggs after tasselling
if younger plants arenot readily available.
Slow-growing hybrids provide awider range of plants that are suit-
able formoths to lay their eggsandare thereforeprone tohigher lev-
elsof infestation. Stemborer larvae (
Photo4
) feedwithin thewhorls
and thereafter enter theplant stem anddevelopingmaize ears.
EDSONNCUBE,
ARC-GrainCrops Institute
1: Fusarium ear rot in awhitemaize earwith
B. fusca
damage.
2: Fusarium ear rot in yellowmaize.
1
2
