Almost 1/3 of the cotton produced in the world is mechanically picked. The two most frequently used mechanical picking systems are stripping and spindle. Strippers have rollers or mechanical brushes that remove entire bolls from the plant and carry along with them a lot of plant material i.e. leaves, burs and branches. Spindle pickers pull the cotton fiber from the open bolls using revolving barbed spindles that entwine the fibers and release them softly to be carried to the basket. 
The first mechanical picker was developed in 1850, but machine pickers were not commercialized for almost another century. Machine picking was introduced in the USA in 1942 and all cotton in the USA has been picked by machine for many decades. Australia also uses 100% machine picking. Most cotton picking in Argentina, Brazil, Colombia, Greece, Spain and Turkey is also mechanized.