text: Even when fully grown, pear trees bear less fruit than apples, which is one reason that perry is less common than cider. When time to harvest comes, pears should be picked before they are ripe and then left to ripen indoors, while apples should be allowed to ripen on the tree. Both apples and pears suffer from fire blight, which can devastate entire orchards, but pears are also susceptible to pear psylla (also known as Psylla pyri). These insects kill the entire pear tree and are very resistant to insecticides, making them a severe problem for pear orchards. Another added complication is that while apples are often harvested mechanically, pears must be harvested by hand, greatly increasing the time and cost of harvesting.
  Perry-making technique
  Traditional perry making is broadly similar to traditional cider making, in that the fruit is picked, crushed, and pressed to extract the juice, which is then fermented using the wild yeasts found on the fruit's skin. Traditional perry making employed querns and a rack and cloth press, in which the pulp is wrapped in cloth before being squeezed with a press. Modern perry production can use a belt press, which is much more efficient for pressing fruit. It works by sending the fruit down a conveyor belt, on which it is then pressed by rollers. The principal differences between perry and cider production are that pears must be left for a period to mature after picking, and the pomace must be left to stand after initial crushing to lose tannins, a process analogous to wine maceration.  Additionally, because of the variation in hardness of the fruit, determining if a pear is ready for pressing than an apple can be more difficult. Also, key chemical compositional differences occur between apples and pears; these factors play a crucial role in prefermentation and fermentation decisions for perry production.