The atoxigenic strains are inserted into a carrier - Agriculture Cultivation aflatoxins the invisable threat in foods and feeds

About the author

Ranajit Bandyopadhyay is a

plant pathologist at IITA based

in Ibadan, Nigeria. He is

responsible for IITA’s Africa-

wide research and

development activities related

to diseases of maize, soybean,

cowpea, cassava, banana, and

yam. His current research on

mycotoxins focuses on

developing an understanding

of their occurrence, the bio-

ecology of toxigenic fungi,

policy and institutional issues,

and methods to manage

mycotoxins with focus on

biological control and

integrated management.

email:

r.bandyopadhyay@cgiar.org

This Technical Innovation

Brief is published by:

SP-IPM Secretariat

SP-IPM@cgiar.org

www.spipm.cgiar.org

Inoculated sorghum grains broadcast in the field.

– R. Bandyopadhyay

The atoxigenic strains are inserted into a carrier

(e.g.

sorghum) which acts as a funga l food source and is applied to

crops 2-4 weeks prior to flowering. For small field s the product

can be tossed onto the crop by hand. The strain profile shifts

from one dominated by aflato xin producers to one in which

atoxigenics dominate, resulting in reduced contamination o f

the crop. The positive influences of atoxigen ic strains carry

over between crops, providing additive effects across years. A

single application benefits not only the treated crop but also

crops in rotation. Additionally, because fungi move throughout

the environment, as the safety level of fungal communities

within treated fi elds improves, so does the safety of fungal

communities in areas neighboring treated fields. Th e

technology also brings benefit s into storage. F irst, there are

fewer aflatoxin-producers moving into the store, and secondly,

the biocontrol agents stay wit h the crop until use. Thus,

competitive exclusion in the fi eld translates into a decreased

risk of contamination during storage and transport.

A technology highly suitable and beneficial for small producers in Africa

Biocontrol in the field has proved a useful method for preventing aflatoxin contamination in maize and groundnut.

The International Institute of Tropical Agricu lture (IITA) conducted trials in Nigeria. Native at oxigenic strains

reduced contamination by up to 99%. The National Agency for Food and Drugs Admin istration and Control

(NAFDAC) gave IITA provisional registra tion to begin testing of the inoculum of a mixture of fou r strains under

the trade name aflasafe™. In 2009, maize farmers who applied aflasafe™ achieved, on ave rage, an 80 %

reduction in aflatoxin contamination at harvest an d 90% after storage. Private and public sector e ngagement is

now necessary to introduce the technology country-wide and at regional level, as with the widely used AF36 and

Afla-Guard™ products in the USA.

When various aflatoxin management practices were evaluated, it was

found that biological control is one of the most cost-effective so lutions

in Africa. Wu an d Khlangwiset (2010) applied health-based analyse s

of cost-effectiveness to the method in Nigeria. Although the analyses

examined only impacts on the incidence of liver cancer, the potentia l

payoff is compelling. Estimating the cost-effectiveness ratio (CER) as

the gross domestic product mu ltiplied by disability-adjusted life years

saved per unit cost, the study revealed that th e CER of treating all

maize fields in Nigeria rated between 5.1 and 9.2, rising to be tween

13.8 and 24.8 if treatment were restricted

consumption.

to maize for

human

aflasafeTM to reduce aflatoxin contamination

in maize. – R. Bandyopadyhay

The reality in future

Biocontrol is hig hly effective, but some contamin ation is inevitable. Thus, aflatoxin management cannot sole ly

rest in biocontro l. It must be ble nded with traditional management as well as th e redirection of contaminate d

crops to alternative use s to avoid human exp osure. Governments and indust ry need to esta blish standard

procedures for effective low-cost testing and alternativ e uses o f contaminated products. Contamination levels

>20 ppb are unsafe for human consumption b ut the crop may still be utilize d for animal feed as long a s

contamination does not exceed 300 ppb in fee d for mature beef cattle or 100 ppb in feed for swine. Other

alternative uses include ethanol production. Wh en such rules a re established, the crop can be managed for

maximum value without risking human exposure to unacceptable aflatoxin concentrations.