The direct costs of thermal defoliation of cotton (heater) are approx. twice as high as of chemical defoliation of cotton, says study. Thermal defoliation may be used for organic cotton, while chemical defoliation is prohibited for organic cotton. Leave defoliation is done before mechanical harvesting to avoid foreign matter in the cotton fiber. A further natural defoliation in colder regions is the defoliation by cold frost. In many African and Asian countries, cotton is still hand-picked. For handpicking cotton, defoliation is not necessary.