Plums are a stone fruit with very smooth, shiny skin, a small pit, and an indent running down one side. While native to Asia, Europe, and America, most U.S. production uses Japanese varieties, which range in color from yellow, red, and blue to almost black. European varieties are blue and purple.
The plum tree plays a significant role in Chinese mythology and is associated with great age and wisdom. Plums are related to the cherry and are members of the rose family. Prunes are dried plums, typically the European type.
References: Agricultural Marketing Resource Center, Michigan State University Extension, Purdue University, USDA.
TYPES, VARIETIES & CUTS
European, Damson, and Japanese are the most common types of plums, each with many varieties. European plums are often used for canning, but are eaten fresh as well. Damson plums are very tart and used primarily for cooking and preserves. Japanese plums are the most common fresh market plums and are grown in California where spring frost injury is unlikely.
PESTS & DISEASE
Rhizopus rot can occur in ripe or near ripe stone fruits kept at 68 to 77°F (20 to 25°C). Cooling and keeping the fruits below 41°F(5°C) is effective against this fungus. Brown rot infection begins during flowering and fruit rot often occurs postharvest. Preharvest fungicide application and prompt cooling after harvest help control infection. Gray mold can be serious in wet spring weather if fruit has harvest and handling wounds. Avoiding mechanical injury and good temperature management are effective control measures.
In eastern growing regions of the United States, oriental fruit moths and oblique banded leaf roller larvae can cause damage. In U.S. western states, katydids bite fruit and leave a white to gray scar that expands as the fruit grows. Also in the West, the light brown apple moth damages the surface of fruit in the lower half and central parts of the tree. The two-spotted mite sucks the contents from leaf cells, causing leaves to appear speckled. Intense infestations cause bronzing or yellowing of the leaves which drop prematurely.
References: Michigan State University Extension, UC Davis Postharvest Technology website, South Australian Research and Development Institute.