Mycotoxins, toxins produced by fungi that colonize food crops, can pose a heavy economic burden to the United States corn industry. In terms of economic burden, aflatoxins are the most problematic mycotoxins in US agriculture. Estimates of their market impacts are important in determining the benefits of implementing mitigation strategies within the US corn industry, and the value of strategies to mitigate mycotoxin problems. Additionally, climate change may cause increases in aflatoxin contamination in corn, greatly affecting the economy of the US Midwest and all sectors in the US and worldwide that rely upon its corn production. We propose two separate models for estimating the potential market loss to the corn industry from aflatoxin contamination, in the case of potential near-future climate scenarios (based on aflatoxin levels in Midwest corn in warm summers in the last decade). One model uses probability of acceptance based on operating characteristic (OC) curves for aflatoxin sampling and testing, while the other employs partial equilibrium economic analysis, assuming no Type 1 or Type 2 errors, to estimate losses due to proportions of lots above the US Food and Drug Administration (FDA) aflatoxin action levels. We estimate that aflatoxin contamination could cause losses to the corn industry ranging from $52.1 million to $1.68 billion annually in the United States, if climate change causes more regular aflatoxin contamination in the Corn Belt as was experienced in years such as 2012. The wide range represents the natural variability in aflatoxin contamination from year to year in US corn, with higher losses representative of warmer years.

Field trials were conducted from 2007 to 2010 to compare grain fumonisin levels among non-Bt maize hybrids and Bt hybrids with transgenic protection against manual infestations of European corn borer (ECB) and Western bean cutworm (WBC). HPLC and ELISA were used to measure fumonisin levels. Results of the methods were highly correlated, but ELISA estimates were higher. Bt hybrids experienced less insect injury, Fusarium ear rot, and fumonisin contamination compared to non-Bt hybrids. WBC infestation increased fumonisin content compared to natural infestation in non-Bt and hybrids expressing Cry1Ab protein in five of eight possible comparisons; in Cry1F hybrids, WBC did not impact fumonisins. These results indicate that WBC is capable of increasing fumonisin levels in maize. Under WBC infestation, Cry1F mitigated this risk more consistently than Cry1Ab or non-Bt hybrids. Transgenically expressed Bt proteins active against multiple lepidopteran pests can provide broad, consistent reductions in the risk of fumonisin contamination.

Mycotoxins are fungal metabolites that contaminate crops, food, and animal feeds. Aflatoxins and fumonisins are among the mycotoxins that have been increasingly reported to affect health and productivity of livestock globally. Given that the health and productivity of livestock can directly influence human food safety and security, a study was conducted to assess the levels and factors for aflatoxin and fumonisin contamination in feed and feed ingredients in Rwanda. Aflatoxins and fumonisins were analyzed in 3328 feed and feed ingredient samples collected at six time points between March and October 2017 in all 30 districts of Rwanda. Of the 612 participants providing samples, there were 10 feed processors, 68 feed vendors, 225 dairy farmers, and 309 poultry farmers. Enzyme-Linked Immunosorbent Assay (ELISA) was used for aflatoxin and fumonisin analyses. Mean aflatoxin levels of 108.83 µg/kg (Median (MD): 43.65 µg/kg), 103.81µg/kg (MD: 48.4 µg/kg), 88.64 µg/kg (MD: 30.90 µg/kg), and 94.95 µg/kg (MD: 70.45 µg/kg) were determined for dairy farmers, poultry farmers, feed vendors, and feed processors, respectively. Mean fumonisin levels were 1.52 mg/kg (MD: 0.71 mg/kg), 1.21 mg/kg (MD: 0.56 mg/kg), 1.48 mg/kg (MD: 0.76 mg/kg), and 1.03 mg/kg (MD: 0.47 mg/kg) for dairy farmers, poultry farmers, feed vendors, and feed processors, respectively. Aflatoxin contamination was significantly affected by time of sampling and district from which feed samples originated (p < 0.05). Fumonisins did not show any correlation trends. Ninety-two percent of survey participants were unaware of aflatoxins and fumonisins and their adverse effects. This study has provided the basic understanding of the extent of feed contamination across the country and has established a baseline for future interventions in Rwanda. Further studies are needed to explore strategies for mitigating mycotoxins in the feed value chain in Rwanda.

Field trials were conducted in 2008, 2009 and 2011 to assess fumonisin contamination in transgenic (Bt) and non- Bt maize hybrids infested with European corn borer, corn earworm, and Western bean cutworm. Comparisons were made among maize hybrids expressing two transgenic insect resistance proteins (Cry1Ab × Vip3Aa), a single resistance protein (Cry1Ab), or no insect resistance. The field design was a randomised complete block design with four replicates of each hybrid × insect combination. Kernel injury, Fusarium ear rot, and fumonisins (FB1+FB2+FB3) in maize grain were measured. These measurements differed significantly among years of the study. In all years, significant positive correlations were present between insect injury and Fusarium ear rot, insect injury and grain fumonisin levels, and Fusarium ear rot and grain fumonisin levels. Under all insect infestation treatments, Cry1Ab × Vip3Aa hybrids were the most resistant of the hybrids with regard to any of the grain quality measurements. Averaged over all insect infestations and years, insect injury, Fusarium ear rot, and grain fumonisin levels were all low in Cry1Ab × Vip3Aa (0.1% and 2.2% of total kernels, and 0.56 mg/kg, respectively). The highest average levels of insect injury, Fusarium ear rot, and grain fumonisin contamination (3.3% and 7.2% of total kernels, and 5.47 mg/kg, respectively) were found in the non-Bt hybrids. The presence of transgenic insect protection (Cry1Ab × Vip3Aa or Cry1Ab) resulted in significant reductions in all grain quality measurements as compared with the non- Bt hybrids. Only grain obtained from Cry1Ab × Vip3Aa hybrids consistently had acceptable fumonisin content according to both US guidance levels and EU regulatory limits. These results indicate that Cry1Ab × Vip3Aa maize hybrids are more likely to yield high quality, low-fumonisin grain compared to hybrids expressing only Cry1Ab or lacking insect resistance.

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