 The cane toad was introduced into New Guinea to control the hawk moth larvae eating sweet potato crops . The first release occurred in 1937 using toads imported from Hawaii , with a second release the same year using specimens from the Australian mainland . Evidence suggests a third release in 1938 , consisting of toads being used for human pregnancy tests — many species of toad were found to be effective for this task , and were employed for about 20 years after the discovery was announced in 1948 . Initial reports argued the toads were effective in reducing the levels of cutworms and sweet potato yields were thought to be improving . As a result , these first releases were followed by further distributions across much of the region , although their effectiveness on other crops , such as cabbages , has been questioned ; when the toads were released at Wau , the cabbages provided insufficient shelter and the toads rapidly left the immediate area for the superior shelter offered by the forest . A similar situation had previously arisen in the Australian cane fields , but this experience was either unknown or ignored in New Guinea . The cane toad has since become abundant in rural and urban areas . 
