Incidence of Leaf Rot Disease of Coconut in Southern Kerala and Its Management

Abstract

The coconut is an important crop in Kerala and contributes substantially to the region's economy. However, its productivity is significantly threatened by leaf rot disease (LRD), primarily caused by major fungal pathogens, such as Colletotrichum sp., Fusarium sp., and Exserohilum rostratum. This study investigated the incidence and management of LRD in coconut palms across the southern districts of Kerala, namely, Thiruvananthapuram, Kollam, and Pathanamthitta. A detailed survey revealed significant regional variations in disease incidence, with Thiruvananthapuram showing the highest rates of LRD. This study identified Colletotrichum sp., Fusarium sp., and Exserohilum sp. as the primary pathogens responsible for LRD, which predominantly affects spindle leaves. Symptomatological observations demonstrated the progression of LRD from initial water-soaked lesions on young leaves to the formation of a characteristic fan-like appearance of the palm crown. Pathogenicity tests confirmed the involvement of the identified pathogens, satisfying Koch’s postulates. The study also explored the efficacy of biocontrol agents, such as Trichoderma sp. (NW2, KAU) and Bacillus amyloliquefaciens (VLY24), which showed significant antagonistic effects on pathogens. Trichoderma sp. (NW2) exhibited the highest inhibition rates among all pathogens, making it a promising candidate for sustainable disease management. These findings highlight the potential of integrated disease management, combining biocontrol agents and chemical treatments, to effectively control LRD in coconut plantations.