FATE OF THIRAM IN AN OIL PALM NURSERY DURING THE WET SEASON

Thiram (tetramethylthiuram disulfide) is a fungicide used to control plant pathogenic fungi such as Rhizoctonia spp, Phythium spp. and Fusarium spp. which often infest oil palm seedlings from the prenursery until the main nursery stage. With increasing applications of thiram in oil palm nurseries, it is necessary to investigate the fate of thiram in the nursery environment. The trial was conducted from July till August 2008, i.e. during the wet season, at the Labu Estate Nursery (Sime Darby), Nilai, Negeri Sembilan. The subplots were treated with thiram at the manufacturer’s recommended dose and at double recommended dose. Thiram residue was detected in the soil at all depths (from 0-50 cm) for both treatment doses on the day of spraying (0 DAT). The amount of residue was observed to decrease with soil depth. Analyses of water and oil palm leaflets within the trial showed that thiram was found at 0 and 3 days after treatment of the trial plots at the recommended and double the recommended doses. The results showed that adsorption and dissipation of thiram were slowly being influenced by the type of soil and the total amount of rain received during the experiment. Run-off and wash-off were the major causes of the loss of thiram residues from the water in the nursery environment and from the leaflets of the oil palm seedlings.