Management practices to minimise pre-harvest aflatoxin contamination in Australian peanuts

Aflatoxin contamination in peanut kernels is a serious food safety issue throughout the world. Stringent implementation of the international regulatory limits for aflatoxin contamination has become a major factor affecting the economic viability of dryland peanut growers in regional Queensland. In this study, the effect of time of harvesting (digging) and threshing on kernel yield, seed grades, aflatoxin contamination and gross returns were examined with peanut (cv. Streeton), grown in large-scale on-farm trials in the Burnett District of Queensland, during the 1997-98 and 1999-2000 seasons. Aflatoxin contamination was widespread during the 1997-98 season because of a severe and prolonged end-of-season drought and associated elevated soil temperatures. During the 1999-2000 season, aflatoxin risk was low at 2 sites because of well-distributed rainfall and lower soil temperatures, in contrast to the other 2 sites where the risk was higher. In both seasons, early harvest and threshing under high aflatoxin risk conditions resulted in consistently lower aflatoxin concentrations and higher gross returns (up to 27%) than in delayed harvesting treatments. However, under low aflatoxin risk conditions crops could be left longer to realise higher potential yield and better seed grades. Indeed, early harvest under low aflatoxin risk resulted in lower gross returns because of lower yields and poorer seed grades. The current study highlighted the importance of assessing aflatoxin risk on a site-by-site basis in order to make appropriate decisions on timing of harvest so as to minimise aflatoxin contamination and maximise gross returns from dryland peanuts.