Pests and Diseases
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Rubus occidentalis is a species of Rubus native to eastern North America. The common name Black Raspberry is shared with the closely related western American species Rubus leucodermis. Other names occasionally used include wild black raspberry, black caps, black cap raspberry, and thimbleberry.
Rubus occidentalis is a deciduous shrub growing to 2–3 m tall, with thorny shoots. The leaves are pinnate, with five leaflets on leaves strong-growing stems in their first year, and three leaflets on leaves on flowering branchlets. The flowers are distinct in having long, slender sepals 6–8 mm long, more than twice as long as the petals. The round-shaped fruit is a 12–15 mm diameter aggregation of drupelets; it is edible, and has a high content of anthocyanins and ellagic acid.
Black raspberries are high in anthocyanins. This has led to them being very useful as natural dyes and, since anthocyanins are powerful antioxidants, to a great deal of interest in them for their potential nutraceutical value. Extensive work has been ongoing at Ohio State University to evaluate their benefit for cancer treatment in mammalian test systems, and the first clinical trials on patients with esophageal cancer.
It is also closely related to the raspberries Rubus idaeus and Rubus strigosus, sharing the distinctively white underside of the leaves and fruit that readily detaches from the carpel, but differing in the ripe fruit being black, and in the stems being more thorny. The black fruit makes them look like blackberries, though this is only superficial, with the taste being unique and not like either raspberry or blackberry. In much of the Mid-Atlantic United States, black raspberries are simply called Blackberries, even though they are not.
Commercial growing and processing
The center for black raspberry production is in the Willamette Valley in Oregon. The main cultivar, 'Munger', is grown on about 600 ha (1500 acres). Other cultivars include 'John Robertson', 'Allen', 'Jewel', 'Blackhawk', 'Macblack', 'Plum Farmer', 'Dundee', 'Hanover', and 'Huron'. The plants are summer tipped by hand, mechanically pruned in winter and then machine harvested. The yields are generally low per acre and this is why the fruits are often expensive.
The species has been used in the breeding of many Rubus hybrids; those between red and black raspberries are common under the name purple raspberries; 'Brandywine', 'Royalty' and 'Estate' are examples of purple raspberry cultivars.
The berries are typically dried, frozen or made into purées and juices or processed as colorants. Two well known liqueurs predominantly based on black raspberry fruit include France's Chambord Liqueur Royale de France and South Korea's various manufacturers of Bokbunja.