Abstract
Ceratocystis wilt disease surveys were conducted in three selected Malaysian Acacia mangium plantations. These completed surveys revealed the occurrence of the wilt disease, with the incidence of infection ranging from 7.5% to 13.6%. Signs of wood-boring insects, bark peeling due to squirrel activity, and pruning wounds were often associated with this disease. The fungus most frequently isolated from the diseased trees was the Ceratocystis fungus. The analysis on the morphological characteristics has identified the fungus as Ceratocystis fimbriata complex. Phylogenetic analysis based on the sequences of the ITS, and concatenated sequences of EF1α-βT regions grouped the isolates within the C. fimbriata sensu stricto, in comparison to other C. fimbriata isolates. Pathogenicity tests were conducted on six to nine-month-old healthy A. mangium seedlings by inoculating these seedlings with eight out of the 16 isolates. The results demonstrated that all the isolates were pathogenic, with mortality beginning as early as two weeks after inoculation. However, an ANOVA test indicated a significant difference between the pathogenicity levels among the fungal isolates. The results also showed that pathogen aggressiveness was not correlated with geographical origin. A host range test was also conducted by using C. fimbriata SSB3 and FRIM1162 isolates against several forest plantation species. The findings suggested that only A. mangium was susceptible to C. fimbriata. The other species remained healthy with no symptoms of infection even after seven weeks of treatment, as compared to the A. mangium species, where between 38 to 60% of the inoculated plants had died. This study provides new information on the status of Ceratocystis wilt disease, especially on the occurrence and effects on A. mangium plantation, by giving insights on how to control and manage this ferocious plant pathogen in the future.
Highlights
Malaysia has approximately 700,000 ha of forest plantations that are planted mainly with Acacia mangium
Surveys conducted in the three A. mangium plantations and two trial plots revealed that the wilt disease occurred in the plantations only
The results of this study showed that Ceratocystis wilt disease occurs in A. mangium plantations in other Malaysian states, apart from Sabah
Summary
Malaysia has approximately 700,000 ha of forest plantations that are planted mainly with Acacia mangium. More than ten private companies, with most of them operating in Sarawak, are actively planting A. mangium as a material to produce wood chips and veneers that cater to domestic and international markets. Most of these plantations are presently in their second rotation. The most severe disease encountered in the A. mangium plantations was the red root rot disease associated with Ganoderma spp.; up until now, the condition has remained unresolved
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