Fumonisins in maize in relation to climate, planting time and hybrids in two agroecological zones in Zambia.

Field experiments in the high rainfall zone (HRZ) and the medium rainfall zone (MRZ) in Zambia were designed to determine the natural occurrence of fumonisins (FB1–2) in Zambian maize hybrids, accumulation of FB1–2 resulting from artificial inoculation with Fusarium verticillioides and effects of climate and planting time on FB1–2 in maize. Combined FB1–2 concentrations varied from 0 to 13,050 ng/g, with an overall mean of 666 ng/g. Maize from the HRZ had low incidences of FB1–2-positive samples (mean 41%) which contained FB1–2 below 500 ng/g. In the MRZ, higher incidences (mean 97%) and concentrations (40% of samples >1,000 ng/g) were recorded in two out of three years. There was no correlation between mean location FB1–2 concentrations in individual years and precipitation, number of rain days or monthly precipitation. Postponing the planting time with 10 or 20 days did not significantly affect FB1–2 concentration, but it reduced the yields in some years.