A study from 5 years ago found over 90% of wheat and corn flour samples in Washington, D.C., contained live fungi. Aspergillus  and  Fusarium  are commonly the predominant types of mold found in wheat flour.  Fusarium  will grow on wheat while in the field and is the cause of a disease called blight or scab. Most farmers will use  multiple techniques  to help reduce plant disease. Crop rotation, using resistant varieties and fungicides and minimal irrigation are helpful. Post harvesting, workers sort the grains to remove contaminated wheat before grinding them into flour. While sorting removes most of the contaminated wheat, small amounts of fungi can still make it into the flour. Please realize, the flour you buy at the store is raw flour that still contains live microorganisms. Eating cake batter or cookie dough can lead to fungal ingestion.