Once, Lord Balarama and Lord Krishna along with their cowherd friends heard about the grove of tala tree (now known as palm tree). All of them decided to go there in order to have delicious and juicy fruits. Cowherds were scared of going there as the grove was guarded by a demon in form of a donkey. His name was Dhenuka, who lived there and survived on deer meat. So cowherds asked Balarama and Krishna for help. Balaram started shaking the tree and as a result some fruits fell down on earth, which alerted Dhenuka. The demon attacked and kicked Balarama on his chest with its hind legs while he was collecting fruits from the ground. Balarama in return caught hold the legs and twisted the donkey round and round and tossed him against the palm tree. Dhenuka lost his life with this attack and fell dead. After that Krishna and Balaram went on to slay other demon friends of Dhenuka. Once again the grove became safe for cowherds and their cattle.
Dhenuka was killed by Lord Balarama not by Lord Krishna for two reasons. Firstly only Balarama could set free dhenuka from curse of the sage Durvasa and secondly Lord Krishna had promised to Prahlad maharaj not to kill anybody from his dynasty.