This book delves into the critical challenge of guava fruit canker, a devastating disease caused by Pestalotiopsis psidii that significantly impacts guava yield and quality. Guava (Psidium guajava L.), celebrated as the "apple of the tropics," holds immense economic and nutritional value in tropical and subtropical regions. However, its cultivation faces severe threats from diseases, with canker causing yield losses ranging from 30% to 100%.The work provides an in-depth exploration of the pathogen's isolation, identification, symptomatology, and pathogenicity. It examines the interplay of weather parameters with disease progression and evaluates the efficacy of various fungicides and bio-rationals through in vitro studies. Practical field management strategies are also presented to combat this destructive disease effectively. It offers practical insights to improve guava disease management, promoting sustainable and profitable cultivation of this vital fruit crop.