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Symptoms and signs

The first symptoms of Fusarium head blight occur shortly after flowering. Diseased spikelets exhibit premature bleaching as the pathogen progresses within the head (Figure 2). One or more spikelets located in the top, middle, or bottom of the head may be bleached (Figure 3). Over time, the premature bleaching of the spikelets may progress throughout the entire head.


Figure 2	Figure 3

If the environment is warm and moist, aggregations of light pink/salmon colored spores (sporodochia) may appear on the rachis and glumes of individual spikelets (Figure 4).

Later in the season, bluish- black spherical bodies may appear on the surface of affected spikelets. These bodies are sexual structures of the fungus known as perithecia, and can be seen readily in laboratory cultures on carrot agar medium (Figure 5).


Figure 4	Figure 5

As symptoms progress, the fungus colonizes the developing grain causing it to shrink and wrinkle inside the head (Figure 6). Often, the infected kernels have a rough, wilted appearance, ranging in color from pink, soft-gray, to light-brown (Figure 7).


Figure 6	Figure 7

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