David F. Kendra
Mycotoxin Research Unit
Peoria, Illinois, USA
The Impact of Crop, Pest and
Agricultural Management Practices
on Mycotoxin Contamination of Field
Crops
OECD Conference CHALLENGES FOR AGRICULTURAL RESEARCH, 5-8
April, 2009
Prague, Czech Republic
Mycotoxins
Mycotoxins are highly toxic secondary
metabolites produced by several key fungal
genera on almost all agricultural commodities
worldwide.
Mycotoxin production depends on the fungal
and plant species, environmental conditions
(including moisture and temperature), the
presence of other fungi or microbes and the
presence of insect pests.
The incidence of mycotoxins depends on
geographical area and season.
In general, mycotoxigenic fungi are often divided
into two broad categories:
“Pre-harvest” (field fungi) – Fusarium
“Post-harvest” (storage fungi) – Aspergillus,
Penicillium
Aflatoxins are generally more common in tropical
or semi-tropical regions while fusariatoxins are
more common in temperate climates.
Biomin
Major mycotoxigenic fungi
Fungal
Genus
Species Mycotoxin
Aspergillus A. flavus
A. parasiticus
A. nomius
A. pseudotamarii
Aflatoxin
(B1, B2, G1, G2, M1)
A. ochraceus Ochratoxin A
A. clavatus
A. terreus
Patulin
A. flavus
A. versicolor
Cycolpiazonic acid (CPA)
Fusarium F. proliferatum
F. verticillioides
Fumonisin
(B1, B2, B3)
F. acruminatum
F. avenaceum
F. crookwellense
F. culmorum
F. equiseti
F. gramineaurm
F. sambucinum
F. sporotrichioides
TypeA Trichothecenes
T-2 toxin, HT-2 toxin, diacetoxyscirpenol
Type B Trichothecenes
Deoxynivalenol, Nivalenol, fusareonon-X
F. avenaceum
F. culmorum
F. graminearum
F. sporotrichoioides
Zearalenone
Penicillium P. cyclopium
P. griseofulvum
Cyclopiazonica acid (CPA)
P. expansum
P. patulum
Patulin
P. verrucossum Ochratoxin A
Mycotoxins and Cropping
Systems
Fusarium: Wheat and Maize
Fungal Growth and Mycotoxin
Production
Fungal growth and mycotoxin production are
influenced by many environmental factors.
Different fungal species respond variably to
environmental factors; therefore it is impossible to
describe a standard set of conditions for
maximum growth and mycotoxin production.
Osborne, et. al. IJFM 119(07)103
Mycotoxin Control
Mycotoxins cannot be eliminated from food or
feed supplies; however, their levels can be
substantially reduced using good agricultural and
management practices.
Control measures can occur at several stages:
Pre-harvest
Harvest
Post-harvest
Pre-harvest Control – Plant
Varieties
Seed companies screen for resistance to maize
ear rot and wheat head blight fungi. High quality
seed is essential for a good stand and overall
plant health.
https://www.pioneer.com/growingpoint/eai/product/profiles/PPPImageServlet?prodCd=&prodLnCd=010&langCd=01&smoCd=LK1B&chartTypeCd=DiseasePest&source=GPOINT
Pre-harvest Control – Plant
Varieties
Physical traits, such as husk tightness and ear
orientation after maturity for maize and row
number and beard for wheat may be involved in
resistance.
Pioneer Hi-Bred International, Inc
Penn State University
Pre-harvest Control – Plant
Density
High plant
density creates
stress on
plants due to
competition for
nutrients and
water which
may
predispose
them to
infection by
mycotoxigenic
fungi.
Blandino, et. al. FCR 106(08)234
Pre-harvest Control – Crop
Rotation
Rotating
between crops
that are
susceptible to
the same
mycotoxigenic
fungus should
be avoided in
order to reduce
both plant
disease and
increased
mycotoxin
formation due to
increased
inoculum.
http://www.endure-network.eu
Pre-harvest Control – Residue
Management
Plant residues
act as a
reservoir for
mycotoxigenic
fungi. Proper
residue
management
is critical for
reducing the
risk of
mycotoxin
contamination.
Maiorano, et. al. CP 27(08)182
Pre-harvest Control – Fertilization
Proper plant nutrition is critical for overall plant
health and for reducing the risk of mycotoxin
contamination. In general, poor fertilization
favors mycotoxin formation.
Reid, et. al. Plant & Soil 237(01)1
DO
N (µg/g)
RM = composted manure
SM = uncomposted, stockpiled manure
1997 1998 1999 1997 1998 1999
Silk-channel inoculation
Ea
r ro
t (1
-7)
Pre-harvest Control – Crop
Damage Damage due to disease, insect feeding or
herbicide injury stress crops and favors mycotoxin
formation.
Folcher, et. al. CP 28(09)302
Harvest Control Late season scouting is critical in
order to make informed decisions regarding harvest time. Harvesting maize and wheat at the appropriate time is critical to minimize the risk of mycotoxin contamination.
Early harvest followed by mechanical dry-down results in lower mycotoxin levels. Moisture levels >20% in field dried maize is sufficient for continued Fusariumgrowth and mycotoxin production.
Schedule fields for harvest based on grain moisture as well as crop condition.
Harvest Control Use appropriate equipment in order to minimize
damage to grain during harvest and handling.
Damaged grain allows for ready colonization by
mycotoxigenic fungi and increases the likelihood of
mycotoxin formation.
Moldy kernels are generally less dense than healthy
kernels. Harvested grain quality can be improved by
increasing the combine fan speed which will discard
the poor quality grain.
Avoid contact of harvest machinery with the soil to
prevent accidental contamination of the grain with
mycotoxigenic fungi.
Post - harvest Control After harvest, reduce grain
moisture by artificial drying. Fusarium growth and mycotoxin formation is greatly suppressed at low moisture levels. Reduce moisture levels to below 15% as quickly as possible without causing heat damage to the grain.
Store grain in a moisture proof and well aerated facility. Moisture variability may result in Fusariumgrowth and mycotoxin formation.
Summary
Outbreaks of crop diseases due by mycotoxigenic
fungi with potentially harmful levels of mycotoxins
are difficult to manage due to their
unpredictability.
Mycotoxins cannot be eliminated from food or
feed supplies; however, their levels can be
substantially reduced using good agricultural and
management practices.
Appropriate cultural practices during the growing
season accompanied with timely harvest and
proper storage of the grain after harvest are
critical management tools for minimizing
mycotoxin contamination.
Thank you
