Although the wet harvest has raised concerns around grain quality, apart from some sprouting, the Foundation for Arable Research (FAR) says there should be little cause for concern. The wet harvest has contributed to a higher incidence of sprouting in a number of wheat and barley crops. There are also some areas where grain has been discoloured by weathering and saprophytic fungi which developed when harvest was delayed. However, although it was a difficult harvest, most grain has now been harvested either at low moisture or has been dried and cooled to safe storage moisture content and temperature for long term storage.
Nick Pyke, FAR Chief Executive says “farmers now need to regularly monitor stored grain for both moisture content and temperature in the silo, grain bag or flat storage to ensure they maintain quality. If moisture and/or temperature increase, it is important to ascertain the reason for the increase and aerate and cool grain back to safe levels.”
A further grain quality issue that is often raised after wet harvests is mycotoxins, which are compounds that are toxic to animals and are produced by fungi associated with grain. In New Zealand the most common mycotoxins are produced from the presence of Fusarium species but the incidence of mycotoxin in cereal grain is usually very low. The presence of Fusarium does not mean mycotoxins have formed as only three of the six more common Fusarium species associated with grain produce mycotoxins; and in previous studies, the two most common species in the major cereal grain growing areas do not produce mycotoxins.
Fusarium infections generally occur at flowering and the fungi develop in and on the grain as it matures. The toxin production is believed to be triggered when cool conditions follow conditions that favour fungal growth. In this last season the conditions at flowering did not favour fungal infection in most grain growing areas and, although conditions at harvest may have favoured fungal development, they were not followed by cool conditions. Detecting mycotoxins is not easy as not all Fusarium fungi produce mycotoxin; the presence of Fusarium fungi does not mean that toxins are produced. The detection of the toxins either requires expensive chemistry or the use of test kits.