Abstract

An unknown disease causing mortality of 25-yr-old teak (Tectona grandis) was observed in a plantation at Parambikulam, Kerala, in July 1988. The primary symptom was canker development 3-6 m above ground, followed by leaf yellowing and shedding, and dieback. A survey carried out in July 1988 showed 12 trees in the plantation to be affected, and the number had increased to 16 (including 7 dead) by the following year. The causative organism was identified as Fusarium solani, and successful pathogenicity tests are reported with this organism. Stems of the trees were infested with the pinhead borer Xyleborus similis (Scolytidae) and F. solani was isolated from the beetle, thus implicating it in spread of the disease. A similar disease has been seen in 22-30 yr old teak in a plantation at Sethumadai, Tamil Nadu