Dry bubble

Bubble. The most conspicuous symptom found is described as a globe-like mass of mushroom tissue, a dry bubble.  A single mushroom or a cluster of mushrooms can become a spherical mass of infected tissue covering an entire infected area.  Occasionally as the diseased tissue ages, a few amber drops of liquid may form.  These liquid drops often cause confusion with another fungal disease, wet bubble, caused by Mycogene sp..  However, the difference is that only a few infected mushrooms exhibit the amber drops and for those that do, it is often only a few very small drops.  Wet bubble is characterized by large and numerous amber drops covering the mass of mushroom tissue.  The bubble symptom usually indicates an early and severe infection of the mushroom pin or even before the pin is visible.  The early infection disrupts the growth of the mushrooms tissue preventing it from developing into differential shapes of the stem and cap.
Split Stripe. When infection takes place after the pin begins to develop, and stem is infected, the stem splits as it matures causing a symptom described at split stipe or stem blowout.  The infection disrupts stem elongation on one side of the mushroom, while the healthy side continues to grow normally.  The tissue on the infected side shatters, splits or ruptures causing this characteristic symptom.
Necrotic Spots. This symptom is described as large brown spots with a fuzzy grayish hue in the center.  These spots are usually the diameter of a pencil eraser head to a dime size.  The fuzzy grayish growth covering these spots is the sporulating fungus and surrounding dark brown color helps distinguish it from bacterial blotch disease that is a lighter,  more yellowish brown color.  This symptom usually develops when infection occurred later in the mushroom growth, when pins are larger or a small spot infection occurred on a pinhead surface.
Spotting. A needle pinhead size brown spotting of the mushroom cap is another symptom.  These spots are often confused with spotting from other fungi such as Trichoderma or sometimes bacteria pitting.  This symptom most likely occurs when a small spore load is present and infection occurs later in the pinning process.