Almond hull rot
Rhizopus stolonifer, Monillinia fructicola
The first indication of hull rot usually comes several weeks before harvest, when leaves on a shoot wither and die. Closely examine fruit on this shoot for a brown area on the outside of the hull and either tan fungal growth in the brown area on the inside or outside of the hull (this indicates Monilinia) or black fungal growth on the inside of the hull (this indicates Rhizopus). Fungi invade hulls and produce a toxin that kills the shoot attached to the fruit. Because the shoot is killed, other green fruit on the shoot don't mature and they remain on the tree after harvest. The disease causes dieback of shoots and fruiting wood that reduces productivity in future years.