Effects of harvesting date on aflatoxin contamination in groundnuts in northern Mozambique

Groundnut (Arachis hypogaea L.) is the third most important crop in Mozambique. Despite its importance as food, the presence of mycotoxins, especially aflatoxins has the potential to limit its use in both the human and livestock diet. In this study, the effect of time of harvesting on aflatoxin (AF) contamination were examined at two locations in Nampula and Mapupulo. A split-plot design with four replications was used with three groundnut varieties (ICGVSM 99568, JL-24 and ICGV-SM 01514) as main plots and three harvesting dates (10 days before physiological maturity, at physiological maturity and 10 days after physiological maturity) as the sub-plots. In both locations field observations indicated that on average AF contamination levels were lower at physiological maturity (H2) compared to harvesting too early (H1) ( > 15 ppb) and harvesting too late (H3) ( > 20 ppb). The higher AF contamination levels at H1 were because of higher pod and kernel moisture content and adverse conditions of wet and humid weather which provided a conducive environment for fungal growth and subsequently AF contamination. Delayed harvesting resulted into highest levels of AF contamination compared to H1 and H2. This could be attributed to heavy damage of pods by insects especially termites which provided ready entry of the fungus and consequently AF contamination. Physical damage of pods as a result of dry weather during H3 may also have resulted into the higher AF contamination levels at this harvest time. It is therefore advisable that farmers’ harvest at physiological maturity in order to reduce AF contamination of groundnuts.