A Spatio–Temporal Investigation of Aflatoxin Contamination Risk of Corn in Southern Georgia, USA.

Aflatoxin is a mycotoxin produced by Aspergillus flavus or Aspergillus parasiticus fungi which can contaminate corn. Aflatoxin contaminated corn in food can cause liver cancer in humans and animals, making it worldwide concern. In the U.S., the Food and Drug Administration office has set a limit of 20 ppb, total aflatoxin, for interstate commerce of food and feed. The occurrence of pre-harvest infection by A. flavus or A. parasiticus and subsequent contamination is primarily driven by high temperatures and drought conditions which are related to specific climate and soil conditions. In southeastern USA, corn planted as a summer crop is highly susceptible to aflatoxin contamination. Rainfall variability, high temperatures during the summer and light textured soils can induce drought or water stress which favors aflatoxin contamination. Accurate aflatoxin assessment requires the collection of multiple corn samples, it is expensive and conducted at harvest which does not allow producers to implement in-season adaptation strategies to reduce the risk. Given the cost of aflatoxin analysis, one role of extension services is to identify the areas most at risk of contamination so that all farmers do not need to do a more detailed local study of the contamination risk.

The objective of this study is to investigate the spatial and temporal patterns in weather, soils and the levels of aflatoxin in corn to determine the areas most at risk of contamination. Data come from 53 counties in southern Georgia over a 30 year period (1977-2007). Principal components analysis was used to identify years with similar weather. A local Moran’s I cluster analysis is used to identify statistically significant clusters of contamination. The links between the spatial patterns of contamination and the distribution of sandy soils and the broad patterns in drought stress as identified from NDVI values in satellite imagery are explored.