Predicting Aflatoxin Contamination Risk in Corn with a Generic Drought Index.

Despite pre-harvest aflatoxin contamination in corn (Zea mays L.) being a continuous issue in the Southeastern United States, especially during seasons characterized by high temperature, low humidity and drought, complex interactions between biotic and abiotic stress factors triggering and aggravating the phenomenon, make risk prediction challenging. This study was conducted to determine whether a drought index could be used to predict the risk for pre-harvest aflatoxin contamination in corn as well as to determine risk differences in-season and among sites. Our hypothesis is that as drought conditions during the growing season are changing the aflatoxin risk is also changing. Aflatoxin contamination data used in this analysis were collected from a control experiment conducted at Starkville, Mississippi from 2000 to 20011. Experimental treatments consisted of two soil types (a Leeper silty clay loam, and a Myatt loam), three inoculation methods and three commercial corn hybrids characterized by different aflatoxin susceptibility levels. The Agricultural Reference Index for Drought (ARID) was calculated on daily basis and evaluated as a prediction tool for in season aflatoxin risk assessment. Multiple logistic regression was used to assess aflatoxin risk with weekly ARID values as predictor variables. In season aflatoxin risk changes, as influenced from variation in weekly ARID values, were studied for different soil types and corn hybrids by using logistic analysis. Preliminary results have showed that ARID might be a promising predictive tool to assess aflatoxin risk throughout the growing season. Soil type and hybrid susceptibility to aflatoxin contamination were statistically significant independent factors. Furthermore, this analysis revealed critical in-season windows when changes in drought conditions are affecting the risk for aflatoxin contamination. The finding of this work may be used to: 1) trigger irrigation, if applicable, during critical risk windows, 2) select hybrids based on relative maturities and/or alter planting dates to reduce crop exposure to drought during critical growth stages, 3) select most appropriate hybrids based on soil type, and 4) optimize harvest decision making.