Module 5: Pest and Disease Management
Oil palm pests are animals, usually insects (such as caterpillars), or mammals (such as rats), which cause damage to the palms. Diseases on the other hand, are caused by micro-organisms such as fungi, bacteria and viruses. Pests and diseases can reduce oil palm yield, damage fruit bunches or the palms, and sometimes even kill the palm.
It is important to monitor the plantation at least every two months, to find pest and disease outbreaks as early as possible.
The most common pests and diseases of oil palm in Southeast Asia are:
Rats (cause damage to fruit bunches)
Leaf-eating insects (cause damage to palm leaves)
Rhinoceros beetles (cause damage to the leaves and the growing point of immature palms)
Stem rot (a severe fungal infection of the trunk that can kill the palm)
Good maintenance of the plantation helps prevent the outbreak of pests and diseases. There are several ways in which damage from pests and diseases can be limited, such as:
- Ensuring a healthy cover of soft weeds or legume plants which attract natural enemies of pests
- Ensuring a clean plantation (e.g. no rotting palm trunks) helps prevent Oryctes outbreaks
- Leaving snakes and other predators alive helps keep rats under control
- Ensuring good access to the palms makes it easier to find outbreaks of pests and diseases in an early stage
Pesticides should be used as little as possible, because they will do damage to the useful insects and animals living in and around the plantation. Farmers applying pesticides should always wear full protective clothing.
To carry out pest and disease control efficiently and effectively, the following sections can be used as a helpful guide.
Warning: Herbicides, pesticides and other chemicals are often toxic to humans, animals and palms, and should be used sparingly and with care
- Always follow the rules and regulations as set by the government
- Always read the label carefully before applying chemicals. If you don’t understand entirely, ask the salesman or an extension worker
- When preparing chemicals, follow the instructions on the package carefully
- Application of chemicals should always be carried out wearing full protective clothing including rubber gloves, boots, mask, rubber apron, and safety glasses
- Spraying or trunk injection should be done only by workers who have followed a training course
- Spray equipment should be kept clean and in good shape
- All containers holding chemicals should be labelled according to their content (e.g. “Herbicide: [Name], “Pesticide: [Name]”, etc.)
Never store food in containers that were used for chemicals or fertilisers.
For notes on how to use a knapsack sprayer, see Module 2.
2) Conducting a Pest and Disease Census
In order to find pests and diseases in an early stage, it is necessary to do a regular ‘check’ of the plantation. This check is called a ‘census’. Doing a census correctly requires extensive field training. An effective and simple way to do census in smallholder plantations is not yet available. To learn how to carry out a pest and disease census correctly, discuss with local plantations or refer to: Rankine and Fairhurst, 1999, Oil Palm Field Handbook Mature.
Census is generally performed on all the palms in every tenth row. The key pests and diseases to check for when doing a census include:
- Rats: Damage to bunches in mature palms and young shoots in immature palms
- Rhinoceros beetle: Round holes in leaf bases, deformed leaves with some leaflet tips missing
- Leaf-eating caterpillars: Irregular holes in the leaflets and/or larvae on the lower fronds or the fresh fronds on the stack
- Spear rot, crown disease, bud rot
On a score sheet or notebook, write down what pests and diseases have been observed and on which palms. If signs of pests or diseases are observed, refer to the specific sections of this chapter to decide what to do next.
Every pest census should be recorded in a log book as shown in the example below.
Rats are an important pest in oil palm plantations. They eat the leaf bases of young palms, sometimes even killing the palms. In older palms, rats eat from the ripening fruits in the bunches, causing damage. When these bunches are sold at the mill a deduction will be given because some of the oil is lost. Rats reproduce very fast, so a small population can become a large one in a short period of time. Therefore, it is important to keep the rat population under control.
- To keep rat damage to fresh fruit bunches at a minimum;
- To keep rat populations under control.
Rat damage to fruit bunches kept at less than 10 percent of the bunches damaged.
Note: In smallholder plantations, rat baiting is useful only when neighbouring farmers also participate. Otherwise controlling rats by baiting is not effective.
Timing and frequency
- Monitoring of rat damage: once per two months.
- Rat baiting: when more than 10 percent of the palms/bunches are damaged, provided that neighbours are willing to participate.
- Installing barn owl boxes: Once, in the beginning of rehabilitation.
Labour time required
- Monitoring rat damage: As part of monitoring harvest quality.
- Rat baiting: 2 hours per hectare per round.
- Installing barn owl boxes: One day per five hectares.
Equipment and materials
- Barn owls, barn owl nesting boxes;
- Rat baits.
Farmers and their families, in discussion with extension workers, cooperative and/or local plantation companies
Every rat baiting activity should be recorded in a log book as shown in the example below.
Figure 1: Fruit bunch damaged by rats
4) Rhinoceros Beetle
Rhinoceros beetle (Oryctes rhinoceros) is a pest which mostly infects immature oil palms. While several options are available for chemical treatments to reduce rhinoceros beetle infestation, none of these is currently ‘standard practice’ in plantations. Rhinoceros beetles breed in rotting wood on the plantation floor, so good maintenance of the plantation is essential because it can help to prevent outbreaks.
The damage caused by rhinoceros beetle to immature palms can be recognised as follows:
- Holes are present in the base of the frond
- Fronds bend or ‘break’ where they are damaged
- New fronds are deformed
- Death of the young palm may occur, if the growing point is eaten by the beetle
In mature palms infected with oryctes, the leaves have a typical shape with chunks missing. Leaf tips may also appear triangular
Rhinoceros beetle is a common pest in coconut palms, so if there is a coconut plantation nearby, attacks on oil palm plantations are more likely to occur. Severe infestation by oryctes can kill large numbers of young palms, so good plantation monitoring and maintenance are important.
- Keep damage of rhinoceros beetle at a minimum;
- Control the population by removing breeding sites.
- All dead and rotting wood is removed from the plantation as soon as possible
- A good legume cover crop is established in immature plantations
- Palms are closely monitored; the number of damaged palms is counted
- Chemical or biological control is applied when the damage exceeds 5%
Timing and frequency
- Removal or shredding of dead wood and establishment of a good cover crop should be done during plantation establishment;
- Maintenance is necessary at all times.
Equipment and materials
- Normal maintenance tools
- Wood chipper/shredder (during plantation establishment)
Every pest control activity should be recorded in a log book as shown in the example below.
5) Leaf-eating pests
There are several leaf-eating pests which sometimes infest oil palm plantations. The most important ones in Southeast Asia are bagworms (Pteroma pendula, Metisa plana, Mahasena corbetti), tussock moths (Dasychira spp., Orgyia spp.), and nettle caterpillars (Darna trima, Setora nitens, Setothosea asigna).
Each of these insects eats through the oil palm leaf, so their presence is easily recognisable by the holes in the leaves. In severely infested palms, only the midribs of the leaflets are left, so the palm cannot capture much sunlight and the yield will be strongly reduced. Prevention and management of outbreaks is therefore important.
Natural enemies are insects which kill pests, for example by laying their eggs in the pest larvae. The natural enemies of leaf-eating pests live in the weeds in and around the plantation (see Module 2 for suggestions on how to manage weeds). If all weeds are killed, the natural enemies will die or move away, and outbreaks of leaf-eating pests will become more likely. But even in well-maintained plantations, outbreaks can still occur.
Managing pests requires careful monitoring and the correct use of hazardous chemicals. Both the monitoring and the application of chemicals should be carried out by trained workers. If farmer groups want to establish monitoring and spraying teams, it is necessary to ask for help from extension workers or nearby plantation companies. Here, we discuss only preventive measures, because monitoring and spraying need to be taught in the field by specialised professionals.
Keep leaf-eating insect damage to oil palms to a minimum.
Maintenance of the plantation is up to standard and promotes the biological control of leaf-eating insect populations.
Equipment and materials
Seeds of beneficial plants (White buttercup, Yellow alder, Senna, Winged false buttonweed, Common elephant’s foot, Mexican creeper, Lechosa)
- Planting beneficial weeds: at the start of plantation rehabilitation
- Doing correct weed maintenance: continuously
Every pest prevention activity should be recorded in a log book as shown in the example below.
Ganoderma, also known as basal or upper stem rot, is a fungal infection of the oil palm. In severe cases of a Ganoderma infection, the oil palm dies. Older plantations may have over 50 percent death rates in the event of a severe infestation. While there is no cure for a Ganoderma infection, the spreading of the infection can sometimes be limited through good management.
Ganoderma is spread in two ways:
- Through soil by threads of fungus
- Through air by spores which come from a mushroom (bracket) that grows on the trunk of infected palms
Not all infected palms have brackets on their trunk. When a palm is infected with Ganoderma, different symptoms may be seen, such as a yellowing of the young leaves, an accumulation of several young unopened leaves (spear leaves) in the middle of the canopy, or a ring of dead fronds hanging down along the trunk.
Sometimes palms will stay productive even though they show signs of Ganoderma, but often they die within a year.
To minimise the spread of Ganoderma through a plantation
- Brackets are taken from the infected palms and destroyed
- Soil is mounted around the base of infected palms
- Dead palms are removed from the plantation and burned
- Remediation: Field is left without palms for at least 12 months after felling of old palms
Equipment and materials
- Bush knife (to cut off the brackets)
- Chain saw
- Spade or digging machine
- Removing brackets: As soon as they are observed
- Soil mounting: As soon as signs of Ganoderma infection are observed
- Remediation: After felling, before replanting
Labour time required
- Removal of brackets: A few minutes per palm
- Soil piling: 30 minutes per palm
- Cutting and removing palms: Several hours per palm, depending on the available equipment
Every disease control activity should be recorded in a log book as shown in the example below.
7) Spear Rot, Crown Disease and Bud Rot
Spear rot is a fungus infection of the spear leaf or the palm growing point. Spear rot usually occurs when the palm is already damaged, for example by insects. Preventing insect attacks by doing good maintenance in the plantation is the best way to prevent spear rot.
The symptoms of spear rot are a dead or rotting spear leaf. There is currently no cure for spear rot. If the whole growing point is killed by the fungus then the palm will eventually die. In less severe cases, the growing point can recover.
Crown disease mainly attacks young palms (1-4 years after planting) but has been known to persist for up to 10 years. It is still unclear what the cause of crown disease is, but it is clear that some planting materials are more susceptible than others. Buying good planting material and providing sufficient potassium (K), magnesium (Mg) and boron (B) are the best ways to prevent crown disease.
Crown disease can be recognised by a typical bending of the leaves, somewhere in the middle. At the point of bending, leaflets are absent or very small. The palm looks very dense, like a pile of leaves. In very severe cases, all the new leaves become affected and the palm growth and yield in the first years is seriously reduced.
Bud rot (Pudrición de Cogollo or PC in Spanish) is a devastating disease which is found mostly in South and Central America, and sometimes in Africa. The disease starts with the yellowing of the youngest fronds, and a rotting of the spear leaf. In extreme cases, the rot moves down into the growing point of the palm (the ‘heart’, hence the Spanish name which means ‘heart rot’) and the palm may die. If the palm survives, recovery can take months or even years.
Bud rot can be extremely devastating. The disease has wiped out entire plantations, with tens of thousands of hectares being lost within a few years. Despite intensive research, the cause of bud rot remains unknown. Several fungi as well as abiotic factors have been pointed at.
As a management option, it has been common practice to cut away diseased tissue in the early stage of the disease, and to destroy palms that are more severely affected. However, these measures have not prevented the destruction of entire plantations, and overly fast removal of palms might in some cases even have contributed to the severity of the destruction.
Bud rot has not (yet) been found in Southeast Asia.