Fumonisin reduction using fungicides in forage corn cultivation

This study investigated the possibility of a reduced-fumonisin corn cultivation method using two fungicides, azoxystrobin and propiconazole. A field-based cultivation experiment was conducted, wherein Kimimaru and LG3490 corn were cultivated for 2 years with a fungicide applied. In the first year, the use of fungicides reduced the concentration of fumonisin in corn, but in the following years, no fumonisin-reducing effect was observed. Differences in precipitation may be the cause, but details were unknown. Although a minor effect was observed, the results suggested that the method was not wholly effective. Next, in an in vitro incubation experiment, the relationship between fumonisin-producing fungi (Fusarium fujikuroi) and fumonisin production was examined in the presence of two fungicides. Both fungicides reduced F. fujikuroi cell mass in a concentration-dependent manner. Fumonisin production did not decrease noticeably at low fungicide concentrations but at high concentrations. This indicates that a fungicide concentration above a certain threshold is required to suppress fumonisin production. The fumonisin produced per fungal cell mass remained almost constant between 0.1 and 10 mg/L propiconazole, although it decreased to zero at higher propiconazole concentrations. Thus, the propiconazole-induced decrease in fumonisin production was likely caused by a reduction in fungal cell mass. In contrast, fungal cell mass decreased as azoxystrobin concentration increased, and the azoxystrobin produced per cell mass reduced. Thus, fumonisin production was synergistically suppressed by decreased cell mass and production. The results of both experiments did not exhibit the desired level of reduction effect likely because a sufficiently high concentration of fungicide could not be maintained for outdoor cultivation. Various other factors, such as weather conditions, may have affected the disinfectant concentration, leading to the reduced fungicide concentration.