Mycotoxins originating in the preharvest period represent a less studied research problem, even though they are of the utmost practical significance in maize production, determining marketability (within EU limits), and storage ability, competitiveness, and profit rate. In this study, 18-23 commercial hybrids were tested between 2014 and 2021. Natural infection from Fusarium spp. was higher than 1.5%, and for Aspergillus spp. this was normally 0.01% or 0, much lower than would be considered as severe infection. In spite of this, many hybrids provided far higher toxin contamination than regulations allow. The maximum preharvest aflatoxin B1 was in 2020 (at 2286 μg/kg), and, in several cases, the value was higher than 1000 μg/kg. The hybrid differences were large. In Hungary, the presence of field-originated aflatoxin B1 was continuous, with three AFB1 epidemics in the 8 years. The highest DON contamination was in 2014 (at 27 mg/kg), and a detectable DON level was found in every hybrid. FUMB1+B2 were the highest in 2014 (at 45.78 mg/kg). At these low infection levels, correlations between visual symptoms and toxin contaminations were mostly non-significant, so it is not feasible to draw a conclusion about toxin contamination from ear rot coverage alone. The toxin contamination of hybrids for a percentage of visual infection is highly variable, and only toxin data can decide about food safety. Hybrids with no visual symptoms and high AFB1 contamination were also identified. Preharvest control, including breeding and variety registration, is therefore of the utmost importance to all three pathogens. Even natural ear rot and toxin data do not prove differences in resistance, so a high ear rot or toxin contamination level should be considered as a risk factor for hybrids. The toxin control of freshly harvested grain is vital for separating healthy and contaminated lots. In addition, proper growing and storage conditions must be ensured to protect the feed safety of the grain.
Keywords: Aspergillus flavus; Fusarium graminearum; Fusarium verticillioides; aflatoxin; changing environmental conditions; deoxynivalenol; fumonisin; natural infection; natural toxin contamination; preharvest mycotoxins.