Butt rot

The oldest, lowest fronds turn pale and yellow, dry to brown, and hang straight down against the trunk like a skirt instead of dropping off. At the same time the youngest spear leaves (the new fronds before they open) pile up unopened in the middle, and the whole crown looks pale, flattened and one-sided — the palm is starving because its rotten base can no longer feed it.

woody, shelf-like brackets called conks — these are the mushroom, or fruiting body, of the fungus. Young ones start as soft white or cream buttons at ground level; mature ones harden into hoof- or shelf-shaped brackets with a shiny reddish-brown, mahogany-coloured top and a white underside and rim, usually sitting on the trunk base or on an exposed root.

— not solid wood but soft, pale, crumbly and powdery, with dark brown lines running through the light rotted tissue, and often damp to the touch. In the end the palm snaps off or topples right at the base, even while part of the crown is still green.

Yellow fronds on their own can just be hunger (a nutrient shortage) or drought — but those yellow evenly and the base stays hard; butt rot yellows from the bottom up into a hanging skirt AND rots the base. And brackets growing on a dead stump or a fallen log are harmless wood-rotters — the real alarm is a bracket growing on the base of a living palm.

Butt rot strikes older palms in the mid- to late season, not young seedlings. Be most alert on any block that was replanted with palms a second or third time, or cleared from old infected palms — that is where the fungus is waiting in the ground.

Walk a big "W" across the block so you pass through all four corners and the middle, not just the edge by the path. Stop about 10 times, and at each stop look over the palms around you — and any pale or skirted palm you spot anywhere, go straight to it.

At each palm, check two places: the base of the trunk and the exposed roots — look for white buttons or woody brackets and press the wood to feel for soft, hollow or spongy spots; and the crown — look for a build-up of unopened spears and a skirt of dead fronds hanging down.

Because a single sick palm feeds the fungus through its roots into its neighbours, even one palm with a skirt of dead fronds and unopened spears, OR a bracket (conk) at its base, means act NOW — you do not wait for a percentage. Mark that palm with a dab of paint or a peg and act on it.

every time you scout, so you can watch the rot creep down a row from palm to palm through their touching roots. That tells you where to dig your next trench and which neighbours to watch most closely.

The fungus lives on for years in old palm stumps and roots, so before you plant a new palm crop, dig out and burn or destroy every old stump and big root from the palms that stood there before. Never plant a young palm straight into ground still full of old infected debris — that is how most new plantings catch the rot. This clean-up is your single most powerful defence.

Where you can get it, use partially tolerant oil-palm planting material — it resists the rot better, though it does not fully stop it. Feed and water your palms well: a strong, vigorous palm fights off the rot far longer than a starved, stressed one.

Dig a trench around an affected palm and between it and its healthy neighbours to cut the underground root-to-root contact the fungus travels along. For a lightly affected palm, mound fresh soil around the base to push out new roots above the rot — this won't cure it, but it can keep the palm bearing for a season or two more while you plan to remove it.

No fungicide (fungus-killing spray) can reach the fungus deep in the base and roots, which is why none is recommended here — don't waste money on sprays or drenches hoping to save a rotten palm. Put that effort into clean replanting and removing the sources instead. (Because there is no chemical to use, there is no spraying safety gear or pre-harvest waiting period to worry about with this disease — the work is all digging, mounding and burning.)

Once you see the hanging skirt with unopened spears, or a conk at the base, that palm will not recover and it is now infecting its neighbours. Fell it, dig out and burn the whole stump and root plate, and trench around the gap. Replant that spot only after every scrap of infected debris is gone, using tolerant material — and keep a close eye on the palms on either side.