This survey assessed maize ear rot and aflatoxin contamination in the Kakamega region of Kenya. Over 300 farmers were sampled from harvest through storage. Of 1049 ears examined, 419 showed ear rot, mostly from Fusarium fungus. Aflatoxin tests of 116 samples found levels below 6 ppb in all but one, suggesting low preharvest risk. While ear rot prevalence was high, conditions are not optimal for aflatoxin-producing fungi. Proper drying and storage can further reduce contamination risks, ensuring safe, quality maize for the region.

1. Survey of ear rot and aflatoxin contamination
of maize in the Kakamega Region, Kenya
Timothy Tubbs and Dr. Charles Woloshuk
Purdue University, Botany and Plant Pathology Department
Introduction
Farmers in the Kakamega region rely on maize as one
of their major contributors of calories. With an annual
rainfall of 128 cm per year, Kakamega receives an abun-
dance of water throughout the year, which suggest that
the incident of Aspergillus flavus disease is low risk. The
high elevation of the region also provides temperatures
cooler than those conducive for this ear rot. At har-
vest, stalks are either stack into stooks or piled on the
ground so farmers can prepare fields for the next crop.
Ears are brought back to the farmhouse where the husks
are removed. The drying process begins the by plac-
ing the ears on plastic tarps in the sun or inside. The
grain is hand shelled from the ears and drying contin-
ues on the plastic tarps. Rain, which occurs almost daily,
becomes an important factor during grain drying and
storage. Grain dried and stored incorrectly has a high
risk of A. flavus growth and aflatoxin accumulation. Af-
latoxin contamination is a major concern as was seen
with the aflatoxin outbreak in Kenya 2004 resulting in
the death of 125 people (CDC 2004) with a total of 314
cases. My goal in the survey was to assess preharvest
ear rots and determine where along the harvest-to-stor-
age process aflatoxin contamination is most prevalent .
Objectives
1. Assess the prevalence of ear rot in the field
2. Determine aflatoxin contamination from the field-to-
storage
Objective 1
A total of 1049 ears from 230 farms was examined. The ears were
taken from unharvested plants, harvested plants that were either
in a pile or stook, ear outside that were drying or ear inside dry-
ing. Each ear was evaluated for total kernel count and diseased
kernels caused by Fusarium, Aspergillus, Diplodia and other fun-
gi.
Objective 2
Aflatoxin was conducted on 116 samples from field-to-storage.
ThetestswereconductedwithAfla-VAQUA(Vicam)solvent-less
lateral kit. About 50g of corn from each sample was ground in
a Moulinex grinder (Figure 1), and 5 g was extracted with the
Afla-V AQUA solution for 2 minutes. The extract was filtered
to exclude any maize particles, and 100 µL of Afla-V diluent was
mixed with 100 µL of extract in a 1.5 microtube. After briefly
mixing, 100 µL was applied to a Afla-V AQUA lateral flow strip
(Figure 2). After 5 min of incubation at room temp, aflatoxin was
quantified with the Vertu Lateral Flow Reader (Vicam, Figure 3).
The majority of aflatoxin analysis was conducted on unharvested
corn and corn in storage. This was done to determine if aflatoxin
is already present in the field or is accumulating during storage.
Results
Objective 1
The total number of kernels on a individual ear ranged from 16 to 748 with a median of 300 kernels (Table 1). From the 1049 ears
examined, only 419 had signs of ear rot, by Fusarium species causing 83 % of the rot. The severity of Fusarium (Figure 4) rot varied
with a mean of 30.2% of the ear. Ears infected by Diplodia (Stenocarpella species, Figure 5) accounted for 29 ears with a mean severity
of 2.8%. A. flavus (Figure 6) was only found on 3 ears with a mean severity of 0.2% of ear. Lastly, 41 ears were infected by fungi that
could not be determined by visual inspection (Figure 7). The a mean severity of this group was 3.8% (Table 1).
Acknowledgements
Funding provided by USAID
About the Author
Second year Master Student in Dr. Charlie Woloshuk’s lab
working on the effects of maize in hermetic storage on Asper-
gillus flavus growth and accumulation of aflatoxins in maize.
Discussion
From our results was can see that the majority of the ear rots were caused by Fusarium species and not A. flavus. The very low instance of
A. flavus could also be seen with the very low amount of aflatoxin detected. The one case with elevated aflatoxin of 59 ppb was from an ear
with A. flavus present. These results are likely do to the growing environmental conditions found in Kakamega. With the high amount
of rainfall and cool conditions, plants would not be drought or heat stressed, thus less susceptible to A. flavus infection (Guo et al 2008).
There still could be the possibility of aflatoxin accumulation in storage if good practices are not followed.
Objective 2
Of the 116 samples analyzed, 23 sample tested positive for aflatoxin. For all samples with aflatoxin, the concentration was less than 6
ppb except one sample with 58.78 ppb (Figure 8). This sample contained ears that we observed A. flavus-infected kernels. The mean
for unharvested corn was at 0.42 ppb and corn in storage had a mean of 0.26 ppb (Table 2). There was no significant difference be-
tween aflatoxin amounts and sample location. The max concentration for unharvested corn was 3.02 ppb and the max concentration
for stored corn was 5.58 ppb, which were all under the Kenya governmental regulatory limit of 10 ppb.
Materials and Methods
Future work
Dr. Woloshuk conducted this same survey in Senegal in October 2015. Results from this survey are still underway. Our hope is to
formulate suggestions to the farmers in both countries to increase their maize quality. This would include proper harvesting and safe
storage practices.
References
CDC (Centers for Disease Control and Prevention) 2004. Outbreak of aflatoxin poisoning—eastern and central provinces, Kenya, January–July, 2004. MMWR Morb Mortal Wkly Rep 53:790–792.
Guo, B., Chen, Z.-Y., Lee, R. D. and Scully, B. T. (2008), Drought Stress and Preharvest Aflatoxin Contamination in Agricultural Commodity: Genetics, Genomics and Proteomics. Journal of Integrative Plant Biology, 50: 1281–1291. doi: 10.1111/j.1744-7909.2008.00739.x
Abstract
Farmers in the Kakamega region rely on maize as one of their major contributors of calories. With an annual rainfall of 128
cm per year the chance of maize spoilage can be high. Aflatoxin contamination is another major concern as was seen with the
aflatoxin outbreak in Kenya 2004. The goal of this survey was to assess the prevalence of ear rot in the field and aflatoxin con-
tamination from the field-to-storage. Over 300 farmers were sampled with maize samples being taken from the unharvested
plants, harvested ears, shucked ears drying, shelled maize drying and storage. Only those samples with kernels attached to ear
were assessed for disease while samples from all areas were analyzed for aflatoxin. Our results indicate that of the 1049 ears
sampled 419 of them had some form of ear rot. The most abundant ear rot was caused by Fusarium species with 348 of the 419
ears. From our aflatoxin analysis of 116 samples all were under 6 ppb with the exception of one at 59 ppb. This would suggest
that the risk of preharvest aflatoxin contamination is low. From the ear rot data we can start to form recommendations for
farmers that will reduce ear spoilage and increase the amount of quality maize they have for consumption.
Table 1: Analysis of cob, kernel and disease count by location
Table 2: Aflatoxin analysis for all eight locations
Figure 1: Lateral Flow Reader
Figure 2: Lateral Flow StripFigure 1: Moulinex grinder
Figure 6: AspergillusFigure 4: Fusarium
Figure 5: Diplodia Figure 7: Surface Mold
Figure 8: Maize sample with 58.78 ppb