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Preharvest Infection of Corn Silks and Kernels by Aspergillus flavus. Stephen F. Marsh, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; Gary A. Payne, assistant professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Phytopathology 74:1284-1289. Accepted for publication 29 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1284.

Field and greenhouse studies were used to determine the nature of preharvest infection of corn by Aspergillus flavus. Inoculation of external silks that were yellow-brown resulted in more extensive colonization of the silks and a greater number of infected kernels than inoculation of brown silks. In silk-inoculated and uninoculated ears, the pattern of tissue colonization was very similar: growth generally proceeded from the ear tip towards the base, colonizing the silks first, then the glumes and (by the late milk stage) the kernel surfaces but rarely penetrating the cob pith. Silk senescence and the subsequent growth of A. flavus down the silks was rapid in environment chambers at 30/34 C; the fungus reached the base of some ears in 4 days. Under field conditions, equivalent progress took between 4 and 13 days. The mycelium of A. flavus spread quickly from the silks onto the kernel surfaces, forming a clustered distribution. The percentage of kernels colonized within an ear half was correlated (r≥ 0.67 for six of seven harvest dates) with the extent of contamination of the associated silks by A. flavus but showed no relationship to the location or extent of visible insect damage. Internal infection of kernels did not appear until early dent stage.

Additional keywords: infection process, Zea mays.