As you have noted, it is normal for a plum tree to drop excess fruit, but your description of the browned and shrivelled, prune-like fallen plums sounds suspiciously like brown rot.

Brown rot is a fungal disease of top fruit, caused by the fungi Monilinia laxa and M.fructigena. Many ornamental and fruit trees are affected, including apples, pears, plums, cherries, nectarines ...

Certain plum varieties, such as ‘Czar’, 'Jefferson', ‘Ontario’, and ‘President’, have natural resistance to brown rot, providing a more resilient option for growers.

The most common plum tree diseases include black knot, plum pocket, brown rot, plum pox virus, perennial canker, and bacterial leaf spot. Control of black knot requires both prevention and sanitation.

He says growers can spray the trees with fungicides before bud burst in order to help prevent brown rot, but not after. "So what can you do? If the fruit is pretty close to ripening you can ...

The tree, a big-leaved fig 20 metres tall, formerly stood on a slope on Battery Path and was removed "to ensure public safety and prevent a potential spread of brown root rot disease to trees in ...

The most common plum tree diseases include black knot, plum pocket, brown rot, plum pox virus, perennial canker, and bacterial leaf spot. Control of black knot requires both prevention and sanitation.