Skip to main content
Upper Stem Rot is caused by Ganoderma zonatum and related Ganoderma species. It is a variant of the basal-stem-rot disease, but the fruiting bodies appear on the mid-trunk rather than at ground level. It is often overlooked at census because scouts trained to look at the base miss brackets 1 to 3 metres up. In blocks with mixed Ganoderma pressure, both forms need to be recorded together. Regional priority: Same regions as basal Ganoderma. In practice, most Ganoderma monitoring programs treat basal and upper stem rot as one disease with two symptom locations.

​
When oil palm is most vulnerable

Stand age matters as much as with basal Ganoderma. Upper Stem Rot is more common on older palms (10+ years) and on palms with previous trunk wounds from pruning, harvesting, or lightning strikes.

​
How Upper Stem Rot shows in satellite data

  • Individual-palm decline with the same crown signatures as basal Ganoderma - one-sided collapse, hanging fronds, standing spear.
  • Not distinguishable from basal Ganoderma in imagery at typical resolutions. The distinction is made on the ground.
  • Same block-level and cluster-level alert logic as basal Ganoderma.
Scouts trained only on basal brackets miss Upper Stem Rot. Always look up the trunk to a full palm-height during census, not just at the base.

​
Field symptoms

  • Mid-trunk brackets - the same shelf-shaped fruiting bodies as basal Ganoderma, but 1 to 3 metres up the trunk (occasionally higher).
  • Fronds above the infection line collapse while lower fronds and the base may still look healthy - the mirror image of the basal-Ganoderma pattern.
  • Trunk breakage at the infection line during storms - a late-stage indicator.
  • Sap oozing from old wounds where the fungus entered.
  • Same reduced bunch load and eventual palm death as basal Ganoderma.

​
Reduce the damage by

Upper Stem Rot uses the same management program as basal Ganoderma. See Ganoderma (BSR) for the full program. Additions specific to Upper Stem Rot:
  • Avoid trunk wounds - most Upper Stem Rot infections start at old pruning or harvest wounds. Train harvesters to cut petioles cleanly and not to chip the trunk.
  • Do not stack cut fronds against the trunk - decaying frond bases against a living trunk create infection sites.
  • Sanitize pruning tools - clean cutting tools between palms in high-pressure blocks.
  • Report separately from basal Ganoderma at census, but treat under the same sanitation and replanting program.

​
Set an alert for early warning

Turn the diagnosis into a trigger. Roll Upper Stem Rot into the same Ganoderma census - a single visit to each palm records both forms.
Recommended settings for Upper Stem Rot on oil palm:
  • Quarterly census reminder - same schedule as basal Ganoderma. Record trunk-inspection separately for base and mid-trunk.
  • Palm-cluster NDVI drop alert - same as basal Ganoderma. The satellite cannot distinguish the two.
  • High-resolution imagery review twice per year on stands over 10 years old.