A FIELD EVALUATION ON FUNGICIDES APPLICATION TO CONTROL UPPER STEM ROT (USR) DISEASE IN OIL PALM CAUSED BY Ganoderma spp.

Ganoderma spp. causes basal stem rot (BSR) and upper stem rot (USR) diseases in oil palm. In recent years, there has been an increasing report of USR disease in oil palm, which prompted investigation on fungicides application. This study aimed to evaluate the ability of fungicides to control USR-infected palms. The study was conducted on standing oil palm, selected based on the disease severity index (DSI) in the categories of DSI 1 (early infection) and DSI 2 (moderate infection). Two trials were conducted at two different locations in Sarawak (Miri and Sessang), Malaysia. The fungicides, hexaconazole (4.5 g a.i -90 mL) and tetraconazole (7.5 g a.i. -60 mL) were dissolved in 3 L of water; applied using a trunk injector three times at six months interval and followed up with disease assessments conducted at six-monthly intervals. The investigation found that more palms succumbed to USR infection in the control treatment than in the treated USR-infected palms. After 60-months post-treatment, the USR-infected palms treated with hexaconazole gave a lower percentage of dead palms at 33.33% (Miri) and 50.00% (Sessang) compared with USR-infected palms treated with tetraconazole at 66.70% (Miri) and 100.00% (Sessang) and untreated USR-infected palms at 100.00%. The hexaconazole-treated USR-infected palms continued surviving and actively producing fruit bunches. In conclusion, hexaconazole was found to be more effective than tetraconazole. It gave a higher survival rate by ceasing the progress of disease development, resulting in lengthening the productive lifespan of USR-infected palms.