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An <i>A. flavus</i> collection from corn kernels from 11 fields revealed that ~98% (549/562) were mating type <i>Mat1-2.</i> However, 90% of the isolates were in two vegetative compatibility groups (vcgs) so it was unclear if the high infection frequency could be attributed to mating type or to other traits of the two vcgs. To test the hypothesis that mating type was causal, an isolate from the two predominant kernel infecting vcgs and from two vcgs not found in kernels were deployed on wheat seed between two rows of corn at silking. Ears from both rows were harvested and 20 kernel isolates per row per vcg treatment were obtained. These were tested for homology to the applied vcg and for mating type. For each of the vcgs homology ranged from 0-5% indicating that vcg was not a major contributor to infective ability from inoculum on the ground. However, 94% (150/160) of the isolates were <i>Mat1-2</i> mostly of undetermined vcg. Clearly <i>Mat1-2</i> strains appear to have much greater infective ability. <i>Mat1-1</i> and <i>Mat1-2</i> are transcriptional activators and it appears that genes activated by <i>Mat1-2</i> have a role in infection. It is also significant that biological control strains Afla-Guard, AF36, K49, and 5 of our Louisiana biocontrol strains of <i>A. flavus</i> are all <i>Mat1-2</i>. This is consistent with a role for infection by the biocontrol strains to allow expression of intraspecific aflatoxin inhibition of toxigenic wild-type strains in the infection court thereby mediating biological control. <p><p>Keywords: Fungus, Cereals-Grains, Corn