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Impact of Agronomic Factors on Aflatoxin Contamination in Preharvest Field Corn in >Northeastern Mexico. L. A. Rodriguez-del-Bosque, Research Scientist, Campo Experimental Rio Bravo, Instituto Nacional de Investigaciones Forestales y Agropecuarias, Apartado Postal 172, Rio Bravo, Tamaulipas, Mexico 88900. Plant Dis. 80:988-993. Accepted for publication 31 May 1996. This article is in the public domain and not copyrightable. II may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1996. DOI: 10.1094/PD-80-0988.

Infection by Aspergillus flavus and aflatoxin accumulation in field corn, Zea mays, were studied in relation to single and combined cultural practices in northeastern Mexico during the spring and fall growing seasons of 1991, 1992, and 1993. Aflatoxin contamination was greater during the spring when high temperatures occurred during corn reproduction and maturation. Crops grown with the INIFAP crop management system consistently had high yields and low aflatoxin levels (0 to 6 ppb). The INIFAP system included: (i) early planting; (ii) a well-adapted hybrid (H-422); (iii) 55,000 plants per ha; (iv) adequate irrigation; and (v) ear insect control by insecticides. In contrast, crops in the control management system had management practices opposite to the INIFAP system (late planting, hybrid Growers-2340, 75,000 plants per ha, drought, and no insect control) and had lowest yields and significantly increased aflatoxin (63 to 167 ppb). The two factors most associated with enhanced aflatoxin contamination were late planting and ear insect damage. Cultivar and plant density did not significantly affect aflatoxin contamination when combined with the remaining components of the INIFAP system. Irrigation was not fully explored because of rainfall during the experiments. Artificial ear wounding with a nailboard device significantly increased aflatoxin contamination and interacted with high temperatures, which further demonstrated the importance of both temperature stress and ear injury on preharvest aflatoxin contamination.