Click on a stage to see a picture (stages with pictures are in blue). For a detailed explanation of each stage, look below.

1. After infection of an unfertilized ovary by a spore, the fungus develops a structure known as a sphacelium in the area where a seed would normally develop

2. The sphacelium produces honeydew and macro and microconidia, which are exuded outside of the sphacelium. The honeydew is sweet and contains two oligosaccharides, difructosyl-mannitol and fructosyl-mannitol.

3a. Under relatively dry weather conditions, there is a high concentration of difructosyl-mannitol, which inhibits germination of macroconidia within the honeydew. If the honeydew drips onto unfertilized florets, the macroconidia are capable of initiating infection.

3b. Under wet weather conditions (rain, fog) or a very high relative humidity, the macroconidium germinates to produce a short, non-branched conidiophore, upon which a pyriform secondary conidium is formed. This secondary conidium is produced outside of the honeydew and can be moved some distance by wind.

4. Under cool, dry conditions, the sphacelium can differentiate into a sclerotia.

5. Rarely, the sclerotium can produce perithecia, which are structures that contain ascospores. These sexually-produced spores are significant in that they can have different characteristics than the original strain of fungus that produced them.

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