With Monilinia infections, as shown above, Yaghmour said growers will see a brown area on the outside of the hull and often a tan, fungal growth will appear in the brown area on the inside or outside of the hull. (Photo courtesy of UC ANR).
During hull split, the crack in the hull creates an inviting entry point for air- and soil-borne fungi common in most orchards. These fungi are attracted to the nutrients and water in the hull, and once inside the hull these pathogens release toxins that affect the fruiting wood – or spur – on which the hull hangs.