No abstract

Aflatoxins pose a significant public health risk, decrease productivity and profitability and hamper trade. To minimize aflatoxin contamination a biocontrol technology based on atoxigenic strains of Aspergillus flavus that do not produce aflatoxin is used widely in the United States. The technology, with the generic name Aflasafe, has been improved and adapted for use in Africa. Aflasafe products have been developed or are currently being developed in 20 African countries. Aflatoxin biocontrol is being scaled up for use in several African countries through a mix of public, private, and public-private interventions. Farmers in several countries have commercially treated nearly 400,000 ha of maize and groundnut achieving >90% reduction in aflatoxin contamination. This chapter summarizes the biology of aflatoxin-producing fungi and various factors affecting their occurence, including climate change. Various management practices for aflatoxin mitigation are then discussed. These include biological control, which is increasingly being adopted by farmers in several countries. We discuss biocontrol product development and commercialization in various African countries. Subsequently, we highlight some barriers to adoption and other challenges.

The larvae of the black soldier fly (BSFL, Hermetia illucens) efficiently close resource cycles. Next to the nutrient-rich insect biomass used as animal feed, the residues from the process are promising plant fertilizers. Besides a high nutrient content, the residues contain a diverse microbial community and application to soil can potentially promote soil fertility and agricultural production through the introduction of beneficial microbes. This research assessed the application of the residues on plant-associated bacterial and fungal communities in the rhizosphere of a grass-clover mix in a 42-day greenhouse pot study. Potted soil was amended with BSFL residues (BR+) or conventional compost (CC+) produced by Rwandan waste management companies in parallel to residues and compost sterilized (BR-, CC-) by high-energy electron beam (HEEB) as abiotic controls. The fertilizers were applied at a rate of 150  kg N  ha−1. Soil bacterial and fungal communities in both fertilizer and soil were assessed by high-throughput sequencing of ribosomal markers at different times after fertilizer application. Additionally, indicators for soil fertility such as basal respiration, plant yield and soil physicochemical properties were analyzed. Results showed that the application of BSFL residues influenced the soil microbial communities, and especially fungi, stronger than CC fertilizers. These effects on the microbial community structure could partly be attributed to a potential introduction of microbes to the soil by BSFL residues (e.g., members of genus Bacillus) since untreated and sterilized BSFL residues promoted different microbial communities. With respect to the abiotic effects, we emphasize a potential driving role of particular classes of organic matter like fiber and chitin. Indeed, especially taxa associated with decomposition of organic matter (e.g., members of the fungal genus Mortierella) were promoted by the application of BSFL residues. Soil fertility with respect to plant yield (+17% increase compared to unamended control) and basal respiration (+16% increase compared to unamended control) tended to be improved with the addition of BSFL residues. Findings underline the versatile opportunities for soil fertility arising from the application of BSFL residues in plant production and point to further research on quantification of the described effects.

Aflatoxin contamination of several crops is common in tropical and subtropical regions. Maize and groundnut, staples for billions of people, are among the most susceptible to contamination, primarily caused by the fungus Aspergillus flavus. Globally, an estimated 25 percent of aflatoxin-prone crops 1 are contaminated with aflatoxins and/or other mycotoxins. 2 Depending on the dose and exposure period, these toxins can cause severe health detriments in humans and animals. Farmers producing contaminated crops cannot sell to premium markets, including export markets. Many practices can reduce aflatoxin contamination. The use of atoxigenic isolates of A. flavus as biocontrol agents is a highly efficient and practical technology that, when used as the cornerstone of aflatoxin management programs, works best. After more than 15 years of research, the International Institute of Tropical Agriculture (IITA) successfully created a biocontrol solution to address aflatoxin contamination in maize, groundnut, and sorghum in Africa. IITA, along with the US Department of Agriculture-Agricultural Research Service (USDA-ARS), and national institutions, with support from A4NH and other donors, have developed several biocontrol products-with the tradename Aflasafe-for use in maize (10 countries), groundnut (9 countries), and sorghum (in Ghana). Each product contains four atoxigenic isolates native to the target country. These products were developed by identifying friendly fungi that are highly effective at reducing aflatoxin levels, then testing 1 Susceptible crops apart from maize and groundnut include tree nuts, chili peppers, sorghum, sesame seed, figs, among others.

Aflatoxin contamination of staple crops, commonly occurring in warm areas, negatively impacts human and animal health, and hampers trade and economic development. The fungus Aspergillus flavus is the major aflatoxin producer. However, not all A. flavus genotypes produce aflatoxins. Effective aflatoxin control is achieved using biocontrol products containing spores of atoxigenic A. flavus. In Africa, various biocontrol products under the tradename Aflasafe are available. Private and public sector licensees manufacture Aflasafe using spores freshly produced in laboratories adjacent to their factories. BAMTAARE, the licensee in Senegal, had difficulties to obtain laboratory equipment during its first year of production. To overcome this, a process was developed in Ibadan, Nigeria, for producing highquality dry spores. Viability and stability of the dry spores were tested and conformed to set standards. In 2019, BAMTAARE manufactured Aflasafe SN01 using dry spores produced in Ibadan and sent via courier and 19 000 ha of groundnut and maize in Senegal and The Gambia were treated. Biocontrol manufactured with dry spores was as effective as biocontrol manufactured with freshly produced spores. Treated crops contained safe and significantly (P < 0.05) less aflatoxin than untreated crops. The dry spore innovation will make biocontrol manufacturing cost-efficient in several African countries.