Mildew damage (MIL)


Mildew is indicated by grey discolouration on the brush or distal end of the kernel. Mildew damage is a visual grading factor. As mildew damage increases, it begins to encompass the entire kernel.

Procedure for assessment

Mildew damaged kernels in a sample are considered a visual grading factor. The overall soundness of the sample is taken into consideration and compared to the standard sample.


Photograph of mildew damage on CWRS wheat.
In this field of wheat, the grey of the mildew on the heads is clearly visible.
Photograph of mildew damage on individual kernels of Wheat, Canada Western Red Spring.

Mildew damage on individual kernels of Wheat, Canada Western Red Spring.


Mildew is a fungal condition that affects wheat, barley and a number of other grains. It develops in unthreshed kernels of grain, usually under conditions of excessive moisture.

It should not be confused with the disease powdery mildew, which attacks the leaves, reducing yield.

End-use issues

Because mildew is associated with weathering and sprout damage, it is difficult to fully differentiate quality effects from those due to sprout damage. Flour milling performance is lower because flour is darker. Although moderate mildew damage is apparently not a major quality factor, it serves as a very useful flag for wet harvest conditions and potential sprout damage. The discoloration of the seed coat also can be an aesthetic detriment to food applications like breakfast cereals.

For more information on mildew damage access the Grain Research Laboratory paper on Factors affecting processing performance.

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