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Aflatoxin contamination and biodeterioration were examined in 302 samples of dry cowpeas and pigeon peas that were randomly purchased from 9 districts of the Southern Region of Malawi during July and November 2015. Further, the impact of flotation/washing on aflatoxin levels on the pulses was elucidated. Aflatoxin analyses involved immunoaffinity column (IAC) clean-up and HPLC quantification with fluorescence detection (FLD) while legume biodeterioration assessments were done by visual inspection. Aflatoxins were frequently detected in cowpea (24%, max., 66 μg/kg) and pigeon pea (22%, max., 80 μg/kg) samples that were collected in the month of July. Lower aflatoxin incidence of 15% in cowpeas (max., 470 μg/kg) and 14% in pigeon peas (max., 377 μg/kg) was recorded in the November collection. Overall, aflatoxin levels were significantly higher in the pulses that were collected in November. However, there were no significant differences in the total aflatoxin (aflatoxin B (AFB) + AFB + AFG + AFG) levels between the two types of pulses. Remarkably, in 76.2% of the aflatoxin positive cowpea and in 41.7% of the aflatoxin positive pigeon pea samples, aflatoxin G concentration exceeded aflatoxin B Insect damage percentage averaged at 18.1 ± 18.2% (mean ± SD) in the cowpeas and 16.1 ± 19.4% in pigeon peas. Mean discolouration percentage (number of pulses) of the cowpeas and pigeon peas was found to be at 6.7 ± 4.9 and 8.7 ± 6.2%, respectively. Washing and discarding the buoyant fraction was highly efficient in reducing aflatoxin levels; only 5.2 ± 11.1% of the initial aflatoxin level was found in the cleaned samples. In conclusion, cowpeas and pigeon peas sold on the local market in Malawi may constitute a hazard especially if floatation/washing step is skipped.

A study was conducted for 12 months to evaluate the effectiveness of two improved hermetic storage structures against two maize storage pests Sitophilus zeamais and Prostephanus truncatus at Liwufu Research Station, Malawi. The storages were metal silo and hermetic bag; Actellic super dust was included as a control. The treatments (storages) were replicated four times under natural and artificial infestations. Grain stored in metal silo had the lowest mean percentage weight loss, 1.04% to 1.25%, 12 months after storage followed by hermetic bag, 2.46% to 6.64%. Grain treated with Actellic super had the highest weight loss, 4.86% to 18.72%. The study showed that hermetic storage structures can be promoted as effective alternative non-chemical methods of grain storage for small holder farmers in Malawi.

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