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Postharvest Pathology and Mycotoxins

Fungi in U.S. Export Wheat and Corn. D. B. Sauer, Research plant pathologist, U.S. Department of Agriculture, Agricultural Research Service, U.S. Grain Marketing Research Laboratory, Manhattan, KS 66502-2796; C. L. Storey(2), O. Ecker(3), and D. W. Fulk(4). (2)Research entomologist, U.S. Department of Agriculture, Agricultural Research Service, U.S. Grain Marketing Research Laboratory, Manhattan, KS 66502-2796; (3)Statistician, Marketing Research and Development Division, Agricultural Marketing Service, USDA; (4)Chief, Marketing Standards Branch, Federal Grain Inspection Service, USDA. Phytopathology 72:1449-1452. Accepted for publication 30 March 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982.. DOI: 10.1094/Phyto-72-1449.

From January 1977 to December 1978, 1,653 samples of wheat and 1,940 samples of corn were obtained from 79 export elevators as ships were being loaded. Percentages of kernels containing viable storage fungi after surface-disinfection were about ten times higher in corn than in wheat. Aspergillus glaucus was by far the most common storage mold; it was found in nearly every corn sample and in 80% of wheat samples. A. glaucus was present in an average of 21% of 194,000 corn kernels tested, and in 2.6% of wheat kernels. The high incidence of A. glaucus in corn compared to wheat is indicative of the relatively higher moisture contents at which corn is stored and marketed. Aspergillus flavus was found in only 1% of wheat samples, but in 70% of corn samples. Kernel invasion by A. flavus averaged less than 2% in corn and was negligible in wheat. Penicillium spp. were found in 7% of corn kernels and 0.1% of wheat kernels. Percent of kernels with Aspergillus spp. other than A. glaucus and A. flavus averaged slightly less than 1% in corn and about 0.1% in wheat. Samples of both corn and wheat from West Coast ports and wheat from the Texas Gulf ports had lower counts of storage fungi than those from other regions. Other regions were similar except that corn samples from southeastern ports had more infection by A. flavus and more aflatoxin. Percentages of corn kernels with storage fungi were highest in the summer. Also, samples with higher percentages of damaged kernels tended to be higher in invasion by storage fungi. About 10% of ground corn samples displayed bright greenish-yellow fluorescence (BGYF) under a long-wave ultraviolet lamp. One third of the BGYF positives contained detectable aflatoxin; 9% contained 20 ppb or more.