A phenylurea plant growth regulator valued for its defoliant action and its ability to stimulate fruit growth. Applied at critical developmental stages, thidiazuron promotes cell division and fruit sizing in crops such as apples, grapes, and kiwifruit, improving size uniformity and marketable yield; its defoliation effect is exploited in crops like cotton. Like all plant growth regulators, residues on food crops are controlled through approved use patterns, pre-harvest intervals, and maximum residue limits. It exemplifies precisely timed hormonal intervention in modern orchards — effective when integrated with sound crop management.