2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Specific Cooperative Agreement between the Agricultural Research Service (ARS) and the University of Arizona. Additional details of research can be found in the report for the inhouse research project, 6435-42000-020-00D entitled, "Ecological Basis for Aflatoxin Reduction Through Crop Management and Biological Control." This project is directed at developing techniques to evaluate susceptibility of cotton cultivars to aflatoxin contamination during the second phase of contamination in field tests. The second phase occurs when the mature crop is exposed to both high humidity and high temperature. Misting experiments were set up at the Maricopa Agricultural Center of the University of Arizona in 2004 and 2005. Regardless of the quantity of water applied through misting, the test plots failed to increase humidity with the canopy sufficiently to promote cotton boll rotting and aflatoxin contamination. During 2006, a new approach was developed. Rain-in shelters were developed. These shelters allow trapping of humidity within the cotton canopy. Tests to date indicated that the developed approach allows increases to crop canopy humidity. Influences on the fungal infection process and aflatoxin contamination are being assessed during the 2006 crop year. IMPACT: Tools for selecting cultivars resistant to the second phase of contamination are being developed. This accomplishment impacts National Program 108 by providing a means to minimize mycotoxins in commodities with a greater part of the crop harvest meeting Food and Drug Administration (FDA) guidelines for mycotoxin residues.