Enemy of Copra Industry
pp. 63-69 · Read in the full issue
Oryctes Rhinoceros —Number One Enemy of Copra Industry
Blocks on Pages 63 and 65 by Courtesy of South Pacific Commission.
FEW copra planting communities in the South Pacific are now unaware of the ravages of that coconut destroying pest Oryctes rhinoceros —commonly called rhino ceros beetle.
Areas of active infection are now so well distributed throughout the Pacific, that virtually no copra-pro ducing area can consider itself safe from an invasion by the pest.
A recent publication by the Bishop Museum in Honolulu, written by J.
Tinsley Gressitt, an entomologist of that institution, is therefore of great interest to all planters. Mr.
Gressitt pays particular attention to the Palau Islands, where he did his field work, but the history of infection of other territories is also covered and the destructive methods of the beetle are the same in any of the islands, at all events.
The history of Oryctes in the Palau Islands is interesting, as this infestation was in the nature of what Gressitt calls a “biological ex plosion.” The beetle is believed to have been introduced to one of the small central islands of the Group, Koror, by the Japanese during 1942 —probably from Java or Malaya. In five or six years it had spread both north and south to other islands in the Group and it is estimated that in 10 years it had killed 50 per cent, of the coconuts in the entire Group of 109 principal islands.
On Koror, Peleliu and a couple of the other islands it killed all the mature coconuts and of 1,000 new palms planted on Peleliu in 1951, one-third were killed by Oryctes in six months.
The reasons why damage by the beetle was of explosive force is be lieved to be because this group is made up of true oceanic islands which lacked all the natural enemies Orcytes found in its natural Asiatic homeland: and at the same time, the large number of war-killed palms provided ideal breeding places for the pest.
In such circumstances, when there is no competition or limitation of food, giant individuals develop which are about 10 per cent, larger than usual. It is believed now, however, than diminishing larvae food supply and clean-up cam paigns in the area will reduce the high percentage of damage and that the remaining coconuts in the Group are not necessarily doomed.
The life span of a rhino beetle is believed to be about four months, and in favourable circumstances, three generations may develop in one year. A female lays an average 90 eggs in her lifetime and as the sex ratio appears to be about one female to one male, in the course of one year the progeny per original female is something like 186,000
This explains how the coconuts were extermmated in Koror.
The coconut is the favourite and principal food of Oryctes. Mature trees are preferred but when these are lacking the beetle will attack trees less than a year old. And, when there are no more coconuts, it will live in other palms, par ticularly in pandanus. Palms and plants in which beetles have been found include betel-nut, sago, nipa, royal, oil palm, ivory-nut, sugar cane, pineapples and bananas.
Favourite breeding ground is the
standing dead trunks of coconuts killed by adult beetles or by other means. Other breeding grounds are fallen coconut logs, coconut stumps, coconut logs used in the construc tion of houses, bridges, etc., other palms, in almost any other kind of dead wood, under old logs, or com post. One particularly favoured spot is in sawdust piles or pits, as this provides ready-made food for the larvae.
In The South Pacific
IN a section devoted to the beetle in other countries, Gressitt states: In the Pacific, Oryctes rhinoceros has been introduced into Samoa (1909); Wallis Island, 200 miles northwest of Samoa (1931); New
Britain (1942?); Doom Island, be tween Salawati and New Guinea (1936?); Palau (1942); Vavau, Tongan Islands (1951); and near Suva, Fiji (1952).
In 1924 it was introduced into Niuatoputapu (Niuatobutabu o r Keppel) Island, between Samoa and Honga, but by diligent trapping with coconut logs examined twice a week, and by eliminating breeding situations which included long abandoned latrines, the beetle was exterminated from the six-mile square island after more than seven years of effort by Inspector Muller of Tonga.
The beetle is assumed to have reached Niuatoputapu, Wallis, Fiji and Vavau from Western Samoa, and New Britain and Sorong from Amboina, Ceram, or some other island of Indonesia, In New Britain it became a very serious pest after the war, on the Gazelle Peninsula, It now occurs on both sides of the peninsula for as much as 30 miles from Rabaul, and it is reported to be attacking coco nut, oil, betel, and sago palms, and banana plants and roots of cacao seedlings. The beetle was not identified as Orcytes until about 1950, as it was first thought the damage was caused by the great in crease in populations of native rhinoceros beetles [Scapanes aus tralis (Boisduval) ] or S. grosse punctatus Sternberg from mainland New Guinea as a result of abundant
breeding media irl the form of palms killed during the war.
The elephant beetle, Xylotrupes lorquini Schauf. i“gid&on (Linn.)”], had also been suspected by some, in New Britain, as elsewhere, though it is a much less serious pest as to damage and does not bore into the crowns of the palms,
Another rhinoceros beetle, Orycto dsrus coronatus Bates, also in New Britain, was found to be present in situations with Oryctes, and its adults fed upon Oryctes grubs and pupae in captivity (Dun.). Species of this genus are known to attack coconut palms, however.
It has been suggested that Oryctes may have reached New Britain be-
fore the war, possibly about 1937.
S. Dillon Ripley noticed in 1937 what appeared to be Oryctes damage at Rabaul and on Doom Island (Sorong), a trading centre just west of New Guinea, though not on neighbouring islands or the New Guinea mainland.
In New Ireland the beetle was re ported in early 1952 to have been recently establishd on the midwest coast and also on the upper east coast in small numbers (Dun.); and it is now spreading, The beetle presumably reached Vavau Island, Tonga, sometime in
1951, as quite a population was noticed, though in a limited area, when the beetle’s presence was dis covered in mid-February, 1952. As soon as it was noticed, great efforts
Adults, dorsal view; a, male; b, female.
were made by the Tonga Depart ment of Agriculture to eradicate the beetle completely. Groups of men
tried to destroy all breeding places and kill the beetles in all stages.
The same inspector Muller who ex
terminated the beetle from Niua toputapu was put in charge of pperations, but by August, 1952, the infestation covered an area of eight or 10 square km.
Oryctes was discovered in Fiji in March, 1953. It was found at Veisari, 10 km. west of Suva on Viti Levu, and had already infested an area from the Veisari River to both sides of the Tamavua River and more than 2 km. inland, so may have been introduced at least a year earlier.
On the mainland of southern Asia and on the continental Asiatic islands—Ceylon, the Philippines,
Adults, lateral view; a, male; b, female.
Hainan, Formosa, Sumatra, Java, Borneo, Celebes, and other islands of Indonesia —the situation in re gard to Oryctes is quite different from that on such oceanic islands of the Pacific as Palau, Samoa, and Tonga. New Britain, again, pre sents an intermediate situation, since it is a continental island, but non-Asiatic and outside the natural distribution of the beetle.
Thus it is assumed that in Asia various natural enemies, together with factors such as competition for food, tend to keep population of Oryctes at a lower level than in islands to which the beetle has been introduced. In New Britain many of the natural enemies are probably absent, but at least there are more which might potentially help to control the beetle than are naturally present in the oceanic islands.
The fact that mortality of coco nut trees has been 50 per cent, in Palau in 10 years and less than 15 per cent, in Western Samoa in over 40 years emphasises the ex treme importance of abundant larval food supply—which the Palaus had in plenty in the years following 1942 and which, in Samoa, is better under control. Climatic and geological conditions in the two territories have also had some effect on the relative rate of damage.
Control Of Oryctes
In setting out general control measures, Gressitt makes these points:
• Because of its feeding habits (in the crowns of the palms) and because coconuts are a commercial and food crop, destruction of the pest is difficult, if not impossible by chemical means. 9 Elimination or constant in spection of all possible breeding situations is essential. Special care and control must be exercised over
new forest clearings, sawdust, com post, manure and wood piles. Coco nut-log traps can be used but must be rigidly supervised. 9 Natural enemies should be en couraged; these include Scolia wasps, ground beetles, click beetles, histerid beetles, centipedes, owls, woodpeckers, chickens, ducks, other birds, pigs and rodents. When
natural enemies are absent, safe predators such as Scolia and certain caradid and histerid beetles should be introduced. o Rigid quarantine is necessary to prevent the spread of the beetle.
Elimination of palms and breeding places near docks and anchorages would be helpful. Ships from in fested ports should tie up at wharves in non-infested ports only in daylight.. (The adult flies almost invariably only at night). © Large clean stands of vigorous coconuts are less affected by the beetle than mixed stands or scat tered palms around villages where compost and manure accumulate. (“The Coconut Rhinoceros Beetle”. Our copy from the Bernice P. Bishop Museum, Honolulu, Hawaii.)