Mycotoxins Risk in Maize Fields in Relation to Insect and Edaphic Factors in South Dakota

Mycotoxins can occur at concentrations that are above the tolerance level recommended for human and animal consumption in conventional and Bt maize hybrids. The relationship of insect abundance, insect kernel damage and edaphic factors with mycotoxin concentrations in conventional and Bt maize were investigated in eastern South Dakota during 2008 through 2010. Caterpillar abundance and kernel damage were positively related to fumonisin and aflatoxin concentrations in conventional maize in carbaryl treated and untreated plots. However in Bt maize, only deoxynivalenol concentrations were positively related to caterpillar kernel damage in carbaryl-treated plots. Sap beetle abundance was not related to mycotoxin concentrations in conventional or Bt maize; but, kernel damage by sap beetles in Bt maize fields were positively related to deoxinivalenol and zearalenone concentrations in carbaryl-treated plots, and in untreated plots, aflatoxin and zearalenone concentrations were positively related to sap beetle kernel damage. There was no significant relationship between any mycotoxin and sap beetle kernel damage in conventional maize. Corn rootworms abundance and kernel damage showed no relationship to any of the mycotoxins measured in either conventional or Bt maize. Additionally, Rhopalosiphum maidis abundance and its relation to mycotoxin concentrations was assessed, results revealed that 12% and 14% higher numbers in Bt maize than in conventional maize plots in both years of the study were observed, and there were approximately 22% higher aphid numbers in carbaryl-treated plots compared with untreated plots. Only aflatoxin concentrations in conventional maize were positively and significantly related to aphid abundance. In the final study, soil nitrate levels were positively related to fumonisin concentrations in both conventional and Bt maize. Also it was observed that field slope had a statistically significant negative relationship with fumonisin concentrations because as elevation decreased in the field, fumonisin concentrations increased