MYCOTOXINS IN NEW-ZEALAND MAIZE - A STUDY OF SOME FACTORS INFLUENCINGCONTAMINATION LEVELS IN GRAIN

Samples of grain from New Zealand grown maize (Zea mays L.), collected from yield comparison strip trials at harvest during 1992, 1993, and 1994, were analysed for contamination by the Fusarium mycotoxins nival enol (NIV), deoxynivalenol (DON), and zearalenone (ZEN). The samples c ollected in 1992 were also assessed for the incidence of infection by Fusarium spp. The samples mostly represented commercially grown hybrid s, and 12 of the hybrids were sampled more extensively and were collec ted in each year of the study. The incidence of mycotoxin contaminatio n was high in each year, especially by the two trichothecenes, NIV and DON. The levels found in 1992 were generally higher than in 1993 and 1994. Much of this was because of adverse weather conditions during th e 1991/92 season which led to delayed harvest. In each year samples ha rvested after early June tended to have higher contamination levels. I t was also observed in the 1992 season that Fusarium infection levels were higher in the later harvested samples. Some hybrids were more sus ceptible to accumulation of mycotoxin contaminants, and from the 12 ex tensively sampled hybrids, four could be identified which overall had higher toxin levels. These hybrids had a marked impact on the overall contamination levels found in each season studied. The findings of the study indicate that only hybrids less susceptible to mycotoxin contam ination should be used in New Zealand and that cultural practices shou ld be changed to ensure early harvesting of all crops.