Mycotoxins
Background info
What are mycotoxins
§Mycotoxins are highly stable
compounds produced by fungi
and they contaminate food
crops both before and after
harvest,
§Aflatoxins, fumonisins,
zearalenone and trichothecenes
and deoxynivalenol and
nivalenol are mycotoxins that
contaminate maize and are
harmful to both humans and
animals.
§Produced mainly by Fusarium
and Aspergillus spp
How to reduce levels
Host resistant or tolerant varieties are the most cost effective and
practical means of combating the disease.
Avoid planting maize at unacceptably high densities as this increases
stress.
Rotate with non-hosts of the
Fusarium graminearum
species complex
such as legumes, cotton and sunflower.
Harvest early to avoid lodging. Get rid of infected debris to avoid
buildup of inoculum.
Control insects such as stalk borers which may serve as possible
vectors, observing the threshold value of 10% infested plants for
chemical control.
In order to prevent ear rot after harvest, store grain under low moisture
conditions.
Maize that is harvested can be further decayed and contaminated by
the already present
Fusarium
spp. Maize harvested must contain a low
moisture content and the area in which you store the maize must be
kept dry and clean
Ear rots in Maize
§Fusarium ear rots
§Common in maize with bird and insect damage
§Usually have individually diseased kernels
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§White mould
§Dry hot conditions
§Giberella ear rots
§White to pinkish mould
§Cool, wet conditions
§Both over winter in maize residue and in the soil
Background info
§Gibberella ear rots occur where maize
is produced under wet, warm
conditions.
§The fungi in this complex are known
to produce mycotoxins, such as
deoxynivalenol, nivalenol and the
estrogenic metabolite zearalenone,
which are harmful to humans and
livestock.
§Nivalenol and deoxynivalenol are
known protein synthesis inhibitors and
consumption of grain contaminated
with these mycotoxins can cause
anaemia, skin lesions, vomiting,
diarrhoea, and damage to
hematopoietic (liver) tissues in
humans and animals. Zearalenone-
contaminated feed can lead to
animals developing reproductive
problems.
§Aspergillus fungi produce aflatoxins
Mycotoxin information
Mycotoxin type
Fungal origin
Health effects in Humans
Health effects in animals
Aflatoxins (B
1, B2G1,
G
2)
Aspergillus flavus and
parasiticus
Liver damage, live cancer,
immunosuppressive, damage to DNA
-
genotoxic(10 µg/kg)
Liver cancer, immunosuppressive
(50 µg/kg)
Fumonisins
Fusarium
spp,
Fusarium
verticillioides
Oesophageal cancer in humans, liver
toxicity, immunosuppressive (2000
µg/kg)
Carcinogenic, liver and kidney toxicity,
immunosuppressive
(5 000 µg/kg for horses and pets, 10 000 µg/kg
forpigs and50 000 µg/kg for cattleandpoultry)
Trichothecenes(T
-2
HT
-2)
Fusarium spp
Liver damage, live cancer,
immunosuppressive
Liver damage, live cancer, immunosuppressive
Deoxynivalenol (DON)
Fusarium
spp
Anaemia, skin lesions, vomiting,
diarrhoea, and damage to liver damage
(2000 µg/kg)
Anaemia, skin lesions, vomiting, diarrhoea, and
damage to liver damage
(1000 µg/kg for pigs, pets and calves, up to 5000
µg/kg cattle)
Zearalenone(ZEN)
Fusarium
ssp
Hormonal imbalance and reproductive
effects
Carcinogenic, hormonal imbalance and
reproductive effects (500 µg/kg for cattle, 3000
µg/kg for pigs)
Ochratoxin A
Aspergillus and
Penicillium
spp
Upper urinary tract disease,
carcinogenic, liver and cell toxicity
Upper urinary tract disease, carcinogenic, liver
and cell toxicity
(50 µg/kg pigs, 200 µg/kg poultry)
Not found in
our samples
Mycotoxins found in smallholder farmer samples
Area
Village
Name+and+
Surname
Plot+
Description
%+Ear+
rot
µg/kg
DON+
µg/kg
Ochratoxi
n+A+µg/kg
ZEN+++++++++++++++++++++
µg/kg
T2+
µg/kg
HT
-2+
µg/kg
B
1
B
2
B
3
Midlands
Mayizekanye
Fikile-
Maphumolo
Conv-Maize
30
1826
127
313
Fikile-
Maphumolo
CA-Maize
3
976
Nomusa
Shandu
CA-Maize
12
4719
1233
944
Nomusa-
Shandu-
M+Cp
14
587
1409
1446
Babhekile-Nene-
M+Cp
25
539
174
88
4294
SKZN
Madzikane
Cosmos-Xaba-
M+B,-M+Cp
0
2050
Bergville
Ezibomvini
Phumelele-
Hlongwane
CA-Maize
1
157
77
1950
Phumelele-
Hlongwane-
M+SCC
0
183
57
1418
Stulwane
Neliswe-Msele
CA-Maize
0
466
92
57
1665
High
levels
Toxic
levels
MDF mycotoxin samples continued
Samples without detectable levels
Area
Name and Surname
Sample
Bergville
Nelisiwe
Msele*
M(1/3)
Phumelele
Hlongwane*
M+B (2/4)
Sibongile
Mphulo
M+B,M+C,M(1/3)
Zweni
Ndaba
M+B
SKZN
Letha Ngubo
M+B
Cosmos
Xaba*
M
*Have both clean
samples and high
infestations of
Fusarium
More intercropped
legume plots are free
of fusariums than
maize only plots