MORPHOLOGY OF Phytophthora SP. CAUSING STEM CANKER IN NUTMEG AND THE ROLE OF ACTIVATED CHARCOAL AS A BIOLOGICAL CONTROL AGENT

Abstract

Nutmeg (Myristica fragrans Houtt.) is a key Indonesian spice with high export value. However, in recent years, its productivity has decreased significantly due to the outbreak of stem cancer. This study aims to characterize the morphology of Phytophthora sp., the cause of stem cancer in nutmeg plants, and evaluate the effectiveness of activated charcoal from three types of raw materials: coconut shell, pine wood, and walnut shells in suppressing the development of the disease. The research was carried out through field surveys in three nutmeg centre villages on Ambon Island, namely Hatu, Seith, and Toisapu, laboratory observations at the BBP2TP Ambon Mycology Laboratory, and the Clinical and Biotechnology Laboratory of the Faculty of Agriculture UGM. Effectiveness testing was carried out in situ and in vitro. Morphological identification includes observation of sporangium, chlamydospora, and sporangiophore branching using a microscope. The results of the study show that coconut shell charcoal is more effective than pine and walnut charcoal. Phytophthora sp. found in nutmeg displays varying morphological characteristics and differs from previous species: Sporangia average size 17.9 × 11.42 μm, caducous, with simple simpodial branched sporangiophores, so it is suspected to be a new subspecies. Among the three activated charcoals tested, coconut shell proved most effective in reducing stem canker damage. The results may support the development of sustainable nutmeg stem canker control methods.