Photo 1. Characteristic damage done by the coconut rhinoceros beetle, Oryctes rhinoceros, showing V or wedge-shaped sections missing from the fronds eaten by the adults as they tunnel into the crowns of mature palms. (Solomon Islands)
Photo 2. Severe damage to young fronds by adult coconut rhinoceros beetle, Orytes rhinoceros. (Palau)
Photo 3. Close up of characteristic shape of fronds eaten by adult coconut rhinoceros beetle, Oryctes rhinoceros. (Palau)
Photo 4. Holes made by adult coconut rhinoceros beetle, Oryctes rhinoceros, in the base of fronds. Presumably, the holes were made when the leaves were much younger as the beetle tunnelled into the crown of the palm. (Palau)
Photo 5. Breeding site of a coconut rhinoceros beetle, Oryctes rhinoceros, in soil rich in organic material beneath a rotting log.
Photo 6. Close-up of the larva of a coconut rhinoceros beetle, Orytes rhinoceros. Note that the C-shape grubs or larvae grow up to 100 mm.
Photo 7. The adult is jet-black, up to 40 mm long with a prominent horn. Both male and female beetles vary in size, and size cannot be used to distinguish the sexes.
Photo 9. Underside of adult coconut rhinoceros beetle, Oryctes rhinoceros, to show the fuzzy group of hairs at the rear end of the female (left) compared to the male (right).
Photo 10. The grub or larva of a coconut rhinoceros beetle, Oryctes rhinoceros, infected by the fungus Metarhizium. The green areas are where the fungus is sporulating.
Coconut rhinoceros beetle, rhinoceros beetle
Widespread. South and Southeast Asia, Oceania. American Samoa, Fiji, Hawaii, Papua New Guinea, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu, and Wallis & Futuna. The introductions into Guam, Hawaii, mainland Papua New Guinea, and Solomon Islands, is recent.
Coconut is the most important host, but other palm species are attacked, including betel nut, sago palm and oil palm. Banana, Pandanus, sugarcane and tree fern are also hosts.
The adult beetle does the damage, boring into the crown of coconut palms, cutting across young fronds and flowers. When the leaves unfold the damage is seen as V or wedge-shaped areas missing from the leaflets (Photo 1-4).
Oval eggs (3.5 x 4 mm) are laid one at a time, 5-15 cm, below the surface of moist organic materials, such as sawdust, manure, compost and garbage heaps, or above ground in tunnels, debris in axils of coconut fronds, in still-standing but dead and rotten coconut palms, and in the rotten ends of fallen coconut trunks. Logs and stumps of many other kinds of trees are also hosts (Photo 5). The eggs hatch in 8-12 days. The C-shaped larvae or grubs are white then creamy with brown heads (Photo 6). There are three stages lasting 80 to 200 days (depending on quality of the diet), with the third stage up to 100 mm long and 20 mm diameter. The last stage makes a hollow where it feeds, lining it with liquid faecal material, and then pupates. The two pupal stages last 25-40 days.
Adults remain in the ground for 2-3 weeks and then chew their way out. They are black with horns - often shorter than the male (Photos 7-9). Females live about 9 months, and lay about 50 eggs; males live about 5 months. The beetles are nocturnal, flying to the tops of coconuts where they use their mandibles, horn and strong forelegs to tunnel into the crowns. They do not eat the frass from the tunnels; instead, they drink the sap that comes from tunneling.
The damage caused by the beetle results in loss of leaf area, flowers dying, early nut fall and, ultimately, lower yields. Occasionally, the beetles bore through the midribs of fronds, which snap in the wind.
It is difficult to relate damage to lost production. One way is to prune leaves to simulate beetle attack and compare nut yields on healthy palms. Using the relationship between damage and yield calculated elsewhere, work in Samoa showed that a 25% reduction in leaf area resulted in a 25% reduction in nut yield.
Indirect damage also occurs. In Asia and parts of Papua New Guinea, Oryctes attack encourages invasion by Rhynchophorus sp. palm weevils (see Fact Sheet no. 180).
Look for large jet-black beetles up to 40 mm long with prominent horns. Look for tunnels in the crown of coconut palms with frass - often more than one per palm. Look for the V-shape damaged fronds. Use a hooked wire inserted into the tunnel to remove the beetle.
Research into management of Oryctes started in the Pacific islands in the 1960s. Today, the key agent is a virus (Oryctes rhinoceros nudivirus - OrNV) originally from Malaysia and, more lately, a fungus, Metarhizium anisopliae, from the Philippines. Apply control measures if 3-5 beetles occur per ha up to 2 years after planting, and 15-20 beetles per ha thereafter.
Vigilance is needed at seaports and airports against hitchhiking beetles. Inspect regularly coconut palms growing nearby for frass and leaf symptoms. This is particularly important as a new form of the beetle has been found in recent years, and is now present in Guam, Palau, Papua New Guinea, and Solomon Islands. The damage it causes is similar that that done by the beetle that already exists in the Pacific and elsewhere, but it is not susceptible to OrNV. Also, it is thought to be more aggressive and invasive. The FAO/IBPGR Technical Guidelines for the Safe Movement of Coconut Germplasm should be followed when imports of coconuts are made (http://www.bioversityinternational.org/e-library/publications/detail/coconut/).
There are many general predators (pigs, rats, ants and other insects) and scoliid wasp parasites (e.g., Scolia ruficornis ). The nudivirus infects larvae and adults. It was released in Fiji, Samoa and Tonga in the late '60s and early '70s. Adult beetles are dipped in a suspension of ground, infected grubs, and then released to infect grubs in breeding sites, and adults in feeding tunnels. In Guam, spores of Metarhizium anisopliae (imported from the Philippines) are dusted onto beetles, which then contaminate larvae (Photo 10), and other beetles in breeding sites.
Chemical control is uneconomical because of the low value of coconuts per unit area; additionally, it is impractical to apply insecticides except to young palms. If insecticides are needed, use synthetic pyrethroids. Traps with the attractant ethyl 4-methyloctanoate have been used to monitor populations and to give economic control in some countries. Use one trap per 2 ha.
AUTHOR Grahame Jackson
Information from Waterhouse DF, Norris KR (1987) Biological Control Pacific Prospects. Inkata Press. Photos 5-8 Mark Schmaedick, Land Grant Program, American Samoa Community College. Photos 2,3,4,9&11 Joel Miles, Bureau of Agriculture, Republic of Palau. Photo 10 Fred Brooks, University of Hawaii at Manoa.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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