Efficacy of single and mixed treatments of Trichoderma harzianum as biocontrol agents of Ganoderma basal stem rot of oil palm

Two Trichoderma harzianum strains (FA 1132 and FA 1166) were tested as biocontrol agents for basal stem rot in oil palm seedlings artificially infected with the causal pathogen, Ganoderma boninense. The treatment was carried out by applying a Trichoderma-infused surface mulch and periodic applications of a conidial soil drench made from spore suspensions of the respective Trichoderma strains. A disease severity index (DSI) ranging from 0 to 100 was used to assess the disease severity. A single strain application of T. harzianum, FA 1132 gave the best disease suppression with the lowest DSI of 28.35 compared to the infected, non-treated control plants that gave the highest DSI of 86.67. However, FA 1166 as a single application was ineffective, so was the mixture of the two strains. The biological control property of Trichoderma was shown to be strain-specific and not species-specific. In addition, it was found that applying the mixed inocula significantly decreased the performance of FA1132, the choice strain.