Observation 157124: Aspergillus parasiticus Speare

This fungus was found on an almond with Navel Orangeworm larvae inside from a tree near Winters, CA. A.parasiticus and A. flavus have a very similar macroscopic appearance so it is difficult to distinguish them without an oil immersion microscope lens to view the spores. The spores of A. parasiticus are more echinulated (spiny) than A. flavus. Chemotaxonomy is a more reliable way of distinguishing the two species. You run a thin layer chromatography plate to separate the toxins and then view it under a black light. A. parasiticus always makes 2 green spots indicating aflatoxins G1 & G2 plus two 2 blue-green spots indicating aflatoxins B1 & B2. Aspergillus flavus may or may not produce B1 & B2 spots and no G spots because approximately half of A. flavus isolates found are atoxigenic which has led to the development of a biocontrol method by USDA researcher, Peter Cotty, of finding very aggressive strains of atoxigenic A. flavus to grow in mass culture and spread over field crops with toxigenic strain problems. He has found good results from the aggressive atoxigenic strains out competing the toxigenic ones in field trials thus reducing the levels of aflatoxin contamination in the crop.


A parasiticus is the mold in the central zone of each culture plate. There is a Penicillium contaminant in the outer zone.

Proposed Names

84% (1)
Eye3 Eyes3
Recognized by sight
Used references: The Genus Aspergillus by Raper & Fennell p. 369-70. and “Identification of Common Aspergillus Species” by Maren Klich.
Based on chemical features: Thin layer chromatography plates had spots of Aflatoxins B1, B2, G1, & G2 viewed under UV light 365 nm which is consistent with the configuration of A. parasiticus.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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Created: 2014-01-04 21:30:07 AST (-0400)
Last modified: 2017-07-24 01:57:12 AST (-0400)
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