REPLANTING SYSTEM AND TRICHODERMA AS AN EFFECTIVE FORM OF GANODERMA CONTROL AND PROVEN RESULTS Ike Virdiana1, Patra Anjara1, Julie Flood2, Baihaqi Sitepu1, Yonnes Hasan1, Rachmat Aditya1, Stephen Nelson1 1 Sumatra Bioscience, Bah Lias Research Station, Jl Jend A Yani No 2, PO Box 1154, Medan 20111, Indonesia. E: Ike.Virdiana@sumatrabioscience.com ABSTRACT Basal stem rot (BSR) of oil palm (OP) by Ganoderma boninense is the major disease of economic concern in South East Asia. In most fields, the disease first appears after 7- 9 years and then increases causing high mortality of mature palms and losses accumulate up to replanting time. The reduction in the palm stand and low yield of BSR affected palms results in serious economic losses. Most plantations avoid even worse losses through stringent compliance of an integrated management approach. Field management of BSR throughout Indonesia has focused on agronomic and cultural practices plus biological control but rarely long term trials are undertaken to test the effectiveness of these sanitation practices or to prove the effectiveness of biological control. Three long term Ganoderma field trials were established in 1998, 2000 and 2001 at PT PP London Sumatra Indonesia Tbk’s North Sumatra Bagerpang and Dolok estates on mineral soils to investigate methods to reduce palm losses to Ganoderma infection. The objective of these trials was to investigate whether various replanting techniques would help to reduce the rate of palm losses to Ganoderma during oil palm replanting. The 1998 Ganoderma field planted trial was a split-plot design with five replicates, two main plots and three split plots. The main plot treatments compared buried and unburied stems (trunks) that had been inoculated with Ganoderma. Split plot treatments investigated different planting distances of bait seedlings (0.5, 1 and 1.5 meters away from the trunk). The 2001 Ganoderma field planted trial was established at replanting and was a split-plot design with four replicates, two main plots and four split plots. The split-plot size was 50 recorded palms. The main plots compared windrowing 1:1 with 2:1. The split-plots consisted of factorial combinations of a one year fallow, planting immediately, poisoning and not poisoning the previous stand palms. The 2000 shredding field trial investigated four treatments i) windrowing 1:1 with no shredding, ii) windrowing 2:1 without shredding, iii) windrowing 2:1 with shredding the lower one meter of the oil palm trunk which included the bole and iv) complete shredding of both the oil palm trunk and bole. In addition,various trials were initiated to optimize the isolate and application method for use of Trichoderma bio control. A nursery trial established in 2010 investigated twenty-seven treatments with thirteen different isolates tested using two factors (1. application of Trichoderma directly on top of inoculated Rubber Wood Blocks (RWBs) and 2. complete mixing of Trichoderma with the soil in the nursery polybag). The trial had nine replicates with a factorial design. RWBs inoculated with Ganoderma provide an inoculum source in the nursery polybag. The antagonism of Trichoderma to Ganoderma was assessed as percentage of seedlings showing Ganoderma symptoms. In addition, investigation the effectiveness of Trichoderma to antagonize Ganoderma was established using glass chamber technique. Rubber wood blocks were inoculated with Ganoderma were used as inoculum. There are three treatments tested using two application methods (1. application of Trichoderma directly on top of inoculated RWBs and 2. Mixing of Trichoderma with the soil completely). The observation had nine replicates with randomized completely design. After fourteen years of observation (April 2012) of the buried/un-buried trunk trial, infection occurred earlier in the buried trunks and the closer the seedlings were planted to the windrows then the more rapidly the symptoms were observed. After ten years of observation, the fallowing trial has shown that a one year fallow does significantly reduce Ganoderma infection. After eleven years of observation, complete shredding of both the oil palm trunk and bole significantly (p<0.01) reduced Ganoderma infection. In the screening trial, several isolates of Trichoderma significantly reduced the disease compared to the control. This was especially true when the Trichoderma was in direct contact with the Ganoderma inoculum. This was similarly demonstrated using a simple model system of host, antagonist and pathogen. It is concluded that reducing the inoculum level at replanting either by shredding or by fallowing can help to reduce Ganoderma infection in the next generation. It is important not to cover oil palm material, from the old stand, with soil during replanting and to plant seedling as far away as practical, at least 2 m, from the edge of the windrows to delay infection. Further trials on combining shredding and fallowing are on-going. Trichoderma can be selected and usedas effective biological control agents to reduce Ganoderma infection in nursery especially when the antagonist is in direct contact with the Ganoderma inoculum. Further trials are now ongoing in the field to test the effectiveness. Key words: Oil Palm, Ganoderma; Replanting, Burying, Poisoning, Windrowing, Fallowing |