Ganoderma in oil palm: symptoms and control
Basal stem rot, caused by the fungus Ganoderma boninense, is the most damaging disease of oil palm in South East Asia. It passes from root to root and by spores, hides for years before showing a symptom, and gets worse with every planting generation on the same ground. Nothing cures a palm that is already sick; what exists are ways to slow it, contain it, and replant clean.
How the fungus spreads
Infection begins when a healthy palm's roots touch a source of the fungus: a stump, a piece of trunk, or the roots of a sick palm left in the soil. Oil palm roots reach beyond four planting rows, so root contact between palms is almost unavoidable. The fungus also forms fruiting bodies at the base of the stem that release basidiospores, and wind, insects and animals carry those to other palms and to distant estates.
That is why replanted estates are more vulnerable. A 2023 review in Frontiers in Plant Science concluded that the disease returning in the second and third planting generations comes mainly from root remains left behind; even after a tidy clearing, leftover roots can still form fruiting bodies and hold enough inoculum to infect. In Indonesia the Ministry of Agriculture recorded 46,767 hectares of smallholder estate affected across 12 provinces in January 2024, about 34,000 of them in North Sumatra, where the disease has reached the fifth planting generation.
Symptoms you see, and those you do not
The deceptive part is the timing. An infected palm shows nothing for a long while; the first sign in the crown usually appears when the rot inside the stem base is already 60 to 70 percent through. What to watch for:
- Spear leaves that fail to open, standing bunched in the centre of the crown, sometimes three or more.
- Older fronds turning pale yellow, then drying and hanging around the trunk.
- A flattening crown and no new bunches forming.
- Fruiting bodies of the fungus at the stem base. This is a late sign, not an early one; by this stage the base can split and the palm can fall.
The early symptoms are easy to mistake for nutrient deficiency or drought. A young palm with symptoms usually dies within one to two years; a mature one lasts three to five while its yield keeps falling.
Control
Sanitation at replanting
The decisive step happens before the new palms go in: the old stumps and roots are dug out and removed, not left to rot in place. One study cited in the 2023 review recorded basal stem rot ten years after replanting below 1 percent on sanitised land against more than 13 percent where it was not. Field trials by the Indonesian Oil Palm Research Institute (2014) showed that proper root sanitation delayed infection by up to two years, and the hole-in-hole planting system held incidence down for up to seven.
Isolation trenches and soil mounding
A sick palm that is still bearing can be isolated with a trench around it to cut root contact: a 4 by 4 metre trench in the institute's trials stopped spread to neighbours for two years, and the 2023 review puts the depth at about 0.75 metres. A shallow or unmaintained trench is useless. Cutting out the rotten tissue and mounding soil around the stem base extends a sick palm's productive life by up to three years.
Trichoderma and tolerant planting material
The antagonist fungus Trichoderma is used as a biological control in planting holes and around sick palms; in one trial a combined Trichoderma treatment cut leaf and stem-base symptoms by 83 and 89 percent, though most of the evidence is still from the laboratory. No oil palm variety is immune; what exists are more tolerant progenies, and early-detection tools, from laboratory assays to drone surveys funded by the palm oil fund BPDPKS, are not yet ready for estate-scale use.
Questions people ask
- Can a palm with Ganoderma recover?
- No. What can be done is to extend its productive life with mounding and Trichoderma, limit spread with a trench, and remove it with its roots before it infects further.
- Why are replanted estates hit sooner?
- Root remains and stumps from the previous generation keep the fungus in the soil, and the new seedlings' roots touch them. The more planting generations without sanitation, the higher the incidence.
- Is the fruiting body an early sign?
- No. It appears when much of the stem base has already rotted. Earlier signs are spears that fail to open and older fronds yellowing with no nutrient cause.
In the game
Ganoderma is the slow pest in Sawit Simulator. A sick palm infects each neighbour on its planting grid with a small chance every day, and the stump of a dead palm keeps infecting at half strength until it is pulled. New infections also appear on their own in any planted block, more often when the block is full of debris. Young palms pass through the latent and sick stages far faster than mature ones, as in the field, because their trunks are not yet big enough to resist.
The tools follow the real estate: Trichoderma halves spread in one block for 120 days, a trench around one palm cuts its roots off from its neighbours for good, and a sick palm can be pulled and its slot replanted; the plant doctor from the Workshop pulls, replants and doses Trichoderma for you. What is simplified: no spores travel far, there are no tolerant varieties, and symptoms in the game show at once on the block card, whereas in a real estate the disease's silence is the biggest problem.
Sources
- Frontiers in Plant Science 14, 2023, Ganoderma boninense: general characteristics of pathogenicity and methods of control. https://pmc.ncbi.nlm.nih.gov/articles/PMC10363743/
- Biology 11(2), 2022, Review Update on the Life Cycle, Plant-Microbe Interaction, Genomics, Detection and Control Strategies of the Oil Palm Pathogen Ganoderma boninense. https://pmc.ncbi.nlm.nih.gov/articles/PMC8869222/
- Jurnal Fitopatologi Indonesia 10(1), 2014, Indonesian Oil Palm Research Institute, Pengendalian Penyakit Busuk Pangkal Batang Kelapa Sawit secara Kultur Teknis. In Indonesian. https://journal.ipb.ac.id/jfiti/article/view/8516
- Antara, Kementan antisipasi Ganoderma pada tanaman sawit, 31 January 2024 (46,767 hectares affected in 12 provinces). In Indonesian. https://m.antaranews.com/amp/berita/3940563/kementan-antisipasi-ganoderma-pada-tanaman-sawit