Coconut rhinoceros beetle - Oryctes rhinoceros
The coconut rhinoceros beetle (CRB) is a common pest insect in the Pacific. This is the HIGHEST risk pest of coconut in the Pacific, mostly due to a new biotype that is not controlled by the virus isolates that are used for biological control.
Coconut rhinoceros beetle (CRB)
Oryctes rhinoceros (Linnaeus)
CRB are beetles. Beetles have what is known as a complete metamorphic life cycle. This means they go through distinct changes, with body forms that are very different.
CRB adults are active at night.
Normally you don't see the eggs, larvae or pupae as these are buried in the dead coconut logs or trunks or other rotting materials.
The preferred breeding site for CRB are dead standing coconut palms and the entire life-cycle is completed in this situation.
However, adult females will also lay their eggs in a burrow of organic dead or dying material e.g. coconut frond piles or debris and rotten coconut stumps.
Metamorphic life cycle of CRB (© Aubrey Moore, University of Guam)
CRB has two different 'biotypes' in the Pacific, known as CRB-S (biotype susceptible to known virus isolates) and CRB-G (Guam biotype). Sometimes people use the term CRB-P instead of CRB-S.
Externally the adults of both biotypes look identical, but CRB-G is not affected by the viral biocontrol isolates that have been used to control CRB-S. This means CRB-G can reach very high numbers that cause severe damage in palm plantations, and is very difficult to control.
To identify the biotype of CRB in your area, contact SPC in the first instance or Sean Marshall at AgResearch in New Zealand. Biotypes must be identified using genetic tests, which could be done by a number of laboratories around the Pacific. Check with your local biosecurity / quarantine or SPC for more information.
The eggs are laid by adult females in a burrow of organic dead or dying material.
Preferred sites are in dead palm logs, either standing or on the ground, or the stumps of palms.
This preference is in contrast to the Melanesian coconut rhinoceros beetle Scapanes australis, the larvae of which prefer to develop in dead logs and stumps of forest trees adjacent to palms.
Around 4-5 days after the white-brown eggs are laid, the original soft and elongated eggs will expand into a sturdy sphere (ball). They are 3-4 mm in size.
CRB grubs (circled in red) at a breeding site in rotten stump (© Mark Schmaedick, American Samoa Community College)
Larvae are ‘grubs’ with brown heads and legs and a C-shaped creamy-white body that grow up to 100 mm.
Preferred locations for larval development are dead or dying palm logs, either standing or on the ground, or in the stumps of palms.
In 8-12 days the eggs hatch. There are three larval life stages (instars).
Grubs at the end of the 3rd instar tunnel down below where they have been feeding and make a hollow in the soil (or palm trunk) lined with liquid faecal material (frass or insect droppings).
The grub moults to the pupal stage in this hollow before emerging as an adult.
CRB grub (© Mark Schmaedick, American Samoa Community College)
Pupae have most of the external features seen in an adult, with a tough dull yellow-brown membranous (thin, pliable and a little transparent) exoskeleton.
The pupal stage lasts for 20-40 days before the adult beetle emerges. The last part of the pupal stage is when the exoskeleton hardens to become the shiny black adult beetle we can see.
Adult CRB are large black beetles with a distinctive horn and with delicate red-orange hairs on their underside.
Males and females vary in body size (up to 40 mm) and the female horn tends to be shorter.
The horns can also vary in size among individual beetles depending on larval growing environments.
Males and females can also be distinguished by the underside of their body (see image on the left).
Males have a smooth, polished tip of the abdomen.
Females have a clump of rigid red hairs at the tip of the abdomen.
CRB males do not live as long as females.
Adult males live for approximately 5 months.
Females live for around 9 months. The female will mate with several males and will produce 3-4 clutches of 30-50 eggs.
Adult beetles cause damage to palms by boring holes into the central growing point of the crown to feed on the young host tissue sap (juice).
They start by tearing or drilling their way through softer young unopened fronds into the centre of the growing spike where they feed on the sap. They may come out through the base of the frond midrib (10-50 cm from the base). When the damaged young frond opens, and V or wedge shaped sections of the leaf are missing.
Some signs of the presence of the beetle also include excreted plant tissue and insect droppings (frass) emerging from the entrance holes. Holes in the base of frond stems are also commonly seen. But the holes themselves can also be obscured by the base of the fronds.
Distinct horn and red-orange hairs of male CRB (© Durham Field Office, US Forest Health Protection)
Female CRB (left) have a cluster of orange hairs at the tip of their abdomen but males do not (© Pestnet)
Female (left) and male (right) CRB (© Monica Gruber, Pacific Biosecurity)
CRB can target all ages and heights of palms. Palms most severely affected are those at a young age of 1-3 years with small crowns. The growing point in young palms is a large target relative to the size of the palm crown and therefore more susceptible to being destroyed by boring.
Healthy palms older than 1-3 years, including mature and tall (20-30 m) palms have been able to survive light to moderate damage. However, the strength and growth of the crown is seriously reduced.
Secondary infections may also be visible as the bored holes are the perfect environment and for bacteria, fungi and other pathogens as well as breeding sites for weevils.
V-shaped feeding damage on fronds from CRB (© Pacific Biosecurity)
Bored holes at the base of the frond stems (© Pacific Biosecurity)
Historically, uncontrolled populations of CRB was estimated to have killed 50% of palms over a 10 year period, with some islands suffering more than this. Where pest populations are generally under control, the damage CRB causes to palms results in reduced leaf area, early death of flowers and early nut fall, consequently reducing coconut yields.
India has reported at least a 10% loss in coconut yields and other regions have lost one-third of coconut seedlings. In some regions, secondary infections from the CRB damage can have more of an effect than the CRB attack itself, resulting in death of more palms.
Pest control is needed when CRB infest palms. The combination of direct losses (reduced yield) and costs of control results in economic losses. Infestations of CRB result in replanting costs and costly control measures. It has been estimated CRB has caused losses of $1.1 million in South Pacific Territories in 1968 alone.
CRB-G resistance to the bio-control virus has allowed this CRB biotype to grow in numbers and move to new areas where there are fewer natural predators. It has been nicknamed the ‘Palm Killer’ as it can cause devastating damage to palms and within one year destroy entire palm populations. It has been estimated the CRB-G has killed 50% of palms on some islands over a 10 year period.
Damage from the Coconut rhinoceros beetles increases the risk of secondary infections and infestations e.g. by bacteria, fungi, viroids, viruses and weevils, in the crown
Please check with your local biosecurity / quarantine or SPC for up-to-date distribution information.
The coconut rhinoceros beetle has a widespread distribution that varies with the two biotypes. The common CRB-S biotype is susceptible to Oryctes rhinoceros nudivirus, the major biocontrol isolate.
CRB-S is much more widely distributed than the CRB-G biotype. The CRB-G biotype is not susceptible (tolerant or resistant) to the current Oryctes rhinoceros nudivirus isolate used for biocontrol.
CRB-S biotype distribution
American Samoa, Fiji, Hawaii, Papua New Guinea (New Ireland, East New Britain, Markham Valley), Samoa, Solomon Islands (Shortlands, Gizo), Tokelau (Fakaofo, Nukunonu), Tonga, Tuvalu, British Indian Ocean Territory, Palau, Wallis & Futuna, Rota, Guam and Hawaii.
Mauritius, Mayotte, and Reunion.
Bangladesh, Brunei, Burma, Cambodia, Chagos Archipelago, China, Cocos Islands, India, Indonesia, Laos, Malaysia, Maldives, Philippines, Singapore, Sri Lanka, Taiwan, Thailand, and Vietnam.
CRB has been reported from Iran, Oman, Pakistan, and Yemen, although some sources are uncertain about the actual species involved.
CRB-G biotype distribution
The CRB-G biotype was first reported in Guam. Soon after, it was detected in Papua New Guinea (Port Moresby), Hawaii, Japan (Okinawa 1975), Palau, Philippines, Solomon Islands (Guadalcanal, Central Province, North Malaita, Ulawa), and Rota.
The primary origin of CRB-G has not yet been determined. Guam was the first place it was detected, hence the “G” biotype, but it is not likely to have originated on Guam. It most likely moved from Guam to Hawai'i, but the pathways through which it arrived in Papua New Guinea and other locations are not exactly known.
Most importantly, the International Guidelines for transfer of coconut germplasm should be strictly followed to prevent pests and diseases being moved to new locations.
To minimise the spread of CRB:
- Do not move any coconut material or composting organic matter from CRB-affected areas. In the Solomon Islands CRB has likely spread to Malita from Guadalcanal via movement of chicken manure (used to improve soil fertility in Malita).
- Reduce the breeding habitat for adult beetles by breaking up coconut logs and stumps into small pieces which rot down quickly, burning woody debris and covering woody debris with gill netting. See Controlling CRB below for details.
- Regular inspection (every month) and removal of grubs from rotting trunks is also possible for areas were burning not feasible or allowed.
- Unwanted palm material should not be thrown out to sea, as it may be carrying the beetle
- Ensure shipping and cargoes for transport are free of larvae and beetles, especially around light sources which will attract flying beetles at night. A single mated female can start a new pest population if moved to a new location. If a beetle has been attracted onto a ship it may fly to lights on the coast at night at the destination point.
- Export and imports of coconut palm and products (e.g., mats) should be quarantined and inspected for CRB hitchhikers, or fumigated. Nearby infestations should be taken into consideration as beetles can fly 2-4 km and land on cargo.
- Cargoes should be loaded during the day as the beetles are attracted to lights at night.
- Raise awareness of CRB threats by ship crews and other workers at transport hubs on the risk of accidentally carrying beetles (e.g. information for cargo handlers and shipping agents).
- Coconut rhinoceros beetle can hide in agricultural equipment, forestry products, compost matter, etc. This is particularly important if CRB infestation is near the port area.
Risk of CRB outbreaks is increased by cyclones / typhoons, which increase the moisture content of soil, and also increase the amount of dead or dying organic material for breeding sites e.g. fallen, waterlogged palm logs. Larvae and adults can survive on host material floating through ocean currents. At these times special attention should be paid to prevent movement of the beetle.
Surveillance, using bucket traps with pheromone lures is especially important for early detection of CRB, both for new detections or spread within a country. SPC is currently developing standards for surveillance of CRB (see image on the right).
Bucket traps of various sorts can be used for surveillance. If possible the traps should be hung high in the trees, with free air movement so that beetles can detect the lures.
If it is not possible to place traps high in trees, the traps can be extended by PVC or other pipes extending up from the bucket (see image on right). If PVC pipes are not available other materials can be used e.g. hollowed out bamboo poles.
The most likely pathways for entry are either as eggs or small larvae in rotting humus moved with plant material, or as adults attracted to lights on-board vessels.
Traps with pheromone lures can be used as an early detection tool. Mass trapping is not generally very effective - it can used in plantations but the population needs to be low and traps regularly maintained.
Inaccessible infested areas such as dense vegetation and military bases cannot be managed or easily controlled and can act as sources of CRB. Coconut production areas adjacent to these locations should be monitored closely.
For general information on preventing pests and diseases of coconut, see the Prevention section.
Dr Visoni Timote of SPC demonstrates how to use a CRB trap with PVC pipe (© Maria Ronna Luna Pastorizo-Sekiguchi, The Greenhouse Studio, on behalf of SPC)
We strongly recommend an integrated pest management (IPM) approach to the control of all insects, where possible. This is a combination of methods (pesticides, physical controls such as site hygiene and biological controls) to minimise the use of pesticides and minimise the cost of control. Insecticides are not effective at controlling CRB.
Integrated Pest Management (IPM)
The goal of IPM is to keep pest populations to a level below which they cause economic harm. IPM involves using multiple control options together for the economic control of pests (i.e. cultural, natural and chemical).
In an agricultural context the Food and Agriculture Organization defines IPM as "the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimize risks to human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms".
The best way to control CRB is to integrate multiple methods of management and to act swiftly. Invasion can be rapid: the longer you leave it, the greater the damage will be.
Different control methods target different parts of the beetle life cycle, and the methods are used together to complement each other for an integrated control approach.
It is much easier to control the beetle life-stages that take place in the ground (eggs and larvae), rather than in the trees (adults) - i.e. control of breeding sites.
The removal of fallen palm trunks and dead standing palms is essential to reduce breeding grounds. Breaking up the palms into smaller chunks that rot down quickly will also reduce breeding habitat. If possible cut or break up the trunks into smaller pieces, dry them and then burn. Fine chipping will help rot down the wood faster.
Note that it is not always feasible to burn, especially in wet tropical climates. Burning can also be an environmentally unfriendly action in and adjacent to urban areas. If the logs cannot be burned that should be used for something, rather than left to rot in the plantation.
Organic materials should be composted and turned regularly, so the larvae can be completely removed.
When breeding sites cannot easily be removed or treated placement of gill netting to catch entering or exiting adult beetles has been useful and is an affordable method.
Legume ground cover (e.g. Pueraria phaseoloides) over these sites has also been beneficial in reducing the accessibility of adults looking for breeding sites. However, this has not worked well for CRB-G in Solomon islands. In fact it potentially made things worse.
Netting can be placed over debris, compost heaps and other breeding sites. It can also be placed as balls at the base of fronds on short ornamental palms or when the growing tip of the palm is accessible.
Buckets with pheromone can also be used to trap the beetles.
The University of Guam has excellent information on all of these management methods.
Researchers at the University of Guam found that traditional netting used by Guam fishermen (the Tekken net trap) was more effective at catching beetles than pheromone bucket traps.
Tekken net trap used to catch CRB in Guam (© University of Guam)
If you suspect beetles are still within the palm, they can also be removed with hooked wire inserted into burrow and then destroyed.
CRB have general enemies such as birds, pigs, rats, insects including ants and scoliid wasp parasites. However, the most useful biological control has been isolates of the Oryctes rhinoceros nudivirus.
Adults are infected with the virus and then released to spread infection to larvae breeding sites, and to other adults within palms. Unfortunately, CRB G-biotype is resistant to the Oryctes rhinoceros nudivirus. Sanitation of plant materials as described in the cultural methods above is currently the main tool for control and is therefore very important.
Metarhizium maius (formerly Metarhizium anisopliae, a green muscardine fungus) has also been used effectively. Spores can be applied to known breeding sites, or adult beetles dusted with the fungus spores and released to infect larvae and adults in breeding sites. Metarhizium can be purchased in bulk online at websites such as alibaba.com.
Although rats are invasive in the Pacific, especially on islands, they can be important predators of both CRB larvae and adults.
Pesticides are not recommended due to economic cost and impracticality, unless used to protect young palms or in nurseries. If essential, synthetic pyrethroids are recommended.
Lure-based traps can be used for trapping and monitoring and are economically viable (1 trap per 2 hectares). Baited trapping is a useful method in surveillance of plantations for possible breeding and infestations but has minimal effect on the population.
Visit the Co-operative Agricultural Pest Survey (CAPS) to order traps. Up to date survey and identification methods can be found on the CAPS Resource and Collaboration Site. The site has information on Approved Methods including best practices on setting up lure based traps and ordering supplies.
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content reviewed by Sean Marshall, AgResearch New Zealand, July 2018; David Britton, Department of Agriculture and Water Resources, Australia, July 2018; Bob Macfarlane, Solomon Islands, September 2018; Sharon Woruba, Kokonas Indastri Koporesen, Papua New Guinea, October 2018