Common Spear Rot of Oil Palm in Indonesia.

Common spear rot (CSR), which is also known as crown disease, was first reported in Indonesia in the 1920s. It has caused considerable losses in young oil palm plantings, and yet the pathogenic agent has remained elusive. Symptomatic spear leaves were collected from oil palm plantations and farm plots in South Sumatra, North Sumatra, and Bangka-Belitung, Indonesia. Of the 14 different fungi isolated, Fusarium incarnatum, F. solani, an undescribed Fusarium sp., and Ceratocystis paradoxa were isolated most frequently from diseased leaf tissue. F. incarnatum and the undescribed Fusarium sp. were also frequently isolated from healthy leaf tissue, along with Pestalotiopsis microspora and Curvularia affinis. Ceratocystis paradoxa was never isolated from healthy leaf tissue. Koch's postulate experiments showed that C. paradoxa was able to infect wounded oil palm leaves causing a symptom of extensive rotting similar to that found in the field. Although isolated less frequently and less virulent than C. paradoxa, F. sacchari was also capable of causing lesions on succulent wounded, inoculated leaves. For both C. paradoxa and F. sacchari, the disease severity index was greater when the oil palm leaves appeared to have more succulent growth. Likewise, other Fusarium species and other nonfusarial fungi that were usually not pathogenic were weakly virulent on palms with more succulent growth. These findings confirm that C. paradoxa is one pathogen that is associated with CSR of oil palm in Indonesia.