Controlling aflatoxin contamination

Contamination of maize grain by the fungus, Aspergillus flavus, is reaching worrying levels in many areas of West Africa. This infection of grain may be responsible for the rising number of nutritional disorders of children as the fungal toxins, or aflatoxins, are known to be dangerous to human health. A recent survey of farm grain stores in Benin by researchers of the International Institute of Tropical Agriculture (IITA) has revealed high contamination levels. In the north of the country, the researchers found that over half the maize grain had become contaminated after four months in storage. In the south of the country, about one-third of the grain was infected with A. flavus. The researchers noted, too, that farmers seemed unaware that their grain was infected with aflatoxins The different storage systems used in the north and the south of Benin may account for some of the difference. In the north, grain is stored in clay containers with a thatch roof, and these materials may be harbouring the fungal spores from one season to the next. In the south, farmers tend to use more open structures such as raised stacks. The researchers are reluctant to put all the blame on the store structures. Work in the USA has shown that if maize is stressed during the growing season the grain can crack, leaving it vulnerable to infection while still in the field. The difficult growing conditions of the north, with uncertain rainfall, could also be a major cause of infection: the researchers found, in some areas that maize was harvested with A. flavus on the grain. Ways to prevent infection are now being researched: plant breeders are trying to establish whether some cultivars are more tolerant of infection than others, and efforts are being made to see whether storage structures can be improved. Another avenue of research is to see if grain can be treated before it goes into store. Several traditional medicinal plants have been tried, and there has been some success. Spraying a solution made from a mixture of two plant extracts onto the grain as it went into store stopped the growth of the fungus. Leaving the husk on the cobs also seems to help reduce infection. Dr. Kitty Cardwell, who leads the IITA research, feels that the survey showed the problem to be more serious than originally thought. She is convening a conference, which will be held in Cotonou, Benin, next November, to discuss the problem and to bring together researchers, agriculturalists and health workers to review this problem. Biological Control Centre for Africa International Institute of Tropical Agriculture B P 08-0932, Cotonou BENINContamination of maize grain by the fungus, Aspergillus flavus, is reaching worrying levels in many areas of West Africa. This infection of grain may be responsible for the rising number of nutritional disorders of children as the fungal toxins, or..