 In 1920 , the cane toad was introduced into Puerto Rico to control the populations of white @-@ grub ( <unk> spp . ) , a sugarcane pest . Before this , the pests were manually collected by humans , so the introduction of the toad eliminated labor costs . A second group of toads was imported in 1923 , and by 1932 , the cane toad was well established . The population of white @-@ grubs dramatically decreased , and this was attributed to the cane toad at the annual meeting of the International Sugar Cane Technologists in Puerto Rico . However , there may have been other factors . The six @-@ year period after 1931 — when the cane toad was most prolific , and the white @-@ grub saw dramatic decline — saw the highest @-@ ever rainfall for Puerto Rico . Nevertheless , the cane toad was assumed to have controlled the white @-@ grub ; this view was reinforced by a Nature article titled " Toads save sugar crop " , and this led to large @-@ scale introductions throughout many parts of the Pacific . 
