Pears also are afflicted with other bacteria and fungi, as well as other disorders or parasites.
The European pears are sweeter and softer than apples.
Other species are used as rootstock for European and Asian pears and as ornamental trees.
The fruit of pears is produced on spurs, which appear on shoots more than one year old.
Pears are the least allergenic of all fruits.
Other small-fruited pears, distinguished by their precocity and apple-like fruit, may be referred to P. cordate, a species found wild in western France and in England.
Commercially, pears are consumed fresh, canned, as juice, and occasionally dried.
Pears are high in fiber, as well as substantial amounts of potassium, vitamin C, and phytochemicals (the latter of which helps to prevent disease).
Pears may be raised by sowing the seeds (pips) of common cultivated or wild varieties, forming what are known as free or pear stocks, on which choicer varieties are grafted for increase.
Cultivated pears, whose number is enormous, are without doubt derived from one or two wild species widely distributed throughout Europe and western Asia, and sometimes forming part of the natural vegetation of the forests.
The fruit of pears range from celadon green to golden yellow to tawny red (Herbst 2001).
Today, pears are commercially produced in 81 countries on 4.3 million acres, yielding about 18,000 metric tons (39.4 billion pounds) in 2004 (Riegel 2006).
Along with lamb and soya formula, pears form part of the strictest exclusion diet for allergy sufferers.
Pears typically are medium-sized trees, reaching 10 to 17 meters in height, often with a tall, narrow crown.
Most pears are deciduous, but one or two species in Southeast Asia are evergreen.
Summer and autumn pears should be gathered before they are fully ripe; otherwise they generally will not keep more than a few days.