Beetle Infestation
pp. 31-34 · Read in the full issue
In S. Pacific
Established in Wallis Is.
1T is not generally known that Wallis Island (the principal island of the Wallis-Futuna group, just north of Fiji, ad ministered by France) is heavily infested with the Asian Rhinoceros beetle ( Oryctes Rhinoceros).
A valuable report by Mr F Cohic entomologist of the French Institute of Oceania, written in December, 1950 and just distributed by the South Pacific Commission, shows that the beetle reached Wallis lsl a nd in 1931, probably from Western Samoa; and that, owing to app a rent indifference by officialdom and bad agricultural methods by the native coconut planters, it is now in all the districts of Wallis. In thr4 C -°5 CO ?eirs aI Sd m Xnt a ttont was dead or dying. other im portant island, Futuna, was still free of the pest in 1950 Mr cv.r.«re fu 1 vew little h had been d?nJ’ and that fPtWp
indigenous narasfte nr nrldtw
check ™ it was^ fl dflv P S??iSSn to He thlt d fhP pS
the Teetfe il hfrmlels
damage is done bv thi aamage is done by the adult beetle
—and that, as the beetle reproduces itself entirely in decaying vege tation, the removal of all decaying matter from plantations, and con sistent search for and destruction of eggs and larvae, provide a con siderable measure of control.
The section of Mi*. Cohic’s report dealing with methods of control is worth quoting in full;
Mechanical Control
This consists of collecting the in sects at the larval stage. In the well-kept plantation, it is advisable to use traps, which achieve notable results. The method is simple and consists of digging holes of from 3 to 4 square metres in area and 0.75 metres in depth, in which are placed all kinds of vegetable matter (fronds, fibres, etc.), which decom poses very rapidly while maintain ing an excellent degree of humidity.
Such heaps at ground level may also play the same role.
After a month or two of fermen tation, these heaps attract the in sects; they lose their power of attraction about the sixth month.
They must be inspected every two or three months and all forms of the insect found must be destroyed (eggs, larvae, pupae). This may be done by injecting carbon disulphide into the mass.
Some authors, such as Leefmans, propose adding sodium arsenate to the compost; this lakes a long time to disappear and in no way
diminishes the attraction of the site. (This method is not recom mended for the Wallis Islands be cause pigs are there allowed to run loose.) Gockhale advises adding castor oil cake, the odour of which would attract the Oryctes. Where ever trapping and destruction methods may be adopted, this method of baited traps is very effective. Thus, according to Friederichs, 600 traps made of pieces of stem and rachis gave in one year in Samoa: 11,500 fully-grown insects, 220 pupae, 776,000 larvae, 180,000 eggs.
In Indo-China, in Cambodia, the current practice for the protection of young palms, whether single or in a row, consists of fixing to the insertion point of the fronds (that is, in the area attacked by the parasite) pliant branches, or bundles of rice straw. In the morning the insects which had failed to gain a hold are gathered at the foot of the tree.
Chemical Control
Whatever the control measures adopted against larvae, the trees affected must be constantly pro tected, otherwise they are doomed to disappear fairly quickly, the injuries caused by the Oryctes fre quently resulting in rot, and the introduction of injurious parasites (Coleoptera, Diptera, Ants), against which a defence must be put up.
The destruction of the adult in sect within the petiole is carried out
by means of a strong iron wire, which is pushed into the tunnel.
The opening is then blocked with a one-part salt and two-parts sand mixture, plus a plug of clay or mastic.
The best way of making sure of cicatrisation and aseptic preserva tion of the exposed wood is Professor Chavastelon’s method of using bichromate of copper. When this is applied, the wood turns brown through oxidisation and sun light, there is a coagulation of the albuminoids and of the gums, which change to insoluble organic chromates of copper, which block the pores, forming a persistent residue of chromic acid which is gradually liberated by dissociation into basic chromates under the in fluence of the sap and the sur rounding humidity. The chromic acid thus liberated in small quantities serves as a disinfectant without being strong enough to be toxic. It does not impede the functioning of the generative area (cambium). Moreover, the al buminoids, fixed at the chromates state, increase the preservative action of the liquid and complete the rot-proof screen.
The use of insecticides or of insectifuges in the control of Oryctes is obviously possible, but cost of such an operation would probably involve considerably in
creased expenditure. We therefore limit the use of these products to the protection of young plantations, young trees easily reached by small type sprays (Vermorel type). For such protection, the following could also be used: benzine hexachloride (BHC), or benzine hexachloride
combined with sulphur (“sulfure de polychlorocyclane”); synthetic insecticides which have more re pellent and more lasting qualities than DDT.
Biological Control
There is no need to emphasise the neatness of this control method.
Unfortunately, it is subject to so many variable factors that it be comes risky, and is successful only in very rare cases.
The quite dramatic nature of the Rhinoceros” invasion in Samoa and Micronesia has resulted in research into all means of control The anxiety caused in Fiji by the presence of such a parasite in the neighbouring islands, resulting in a visit to Samoa in 1912 from the Entomologist F, P. Jepson, and the taking of Draconian phyto-sanitary quarantine measures which were then successful in protecting this threatened territory.
Subsequently, Dr. K. Friederichs conducted a detailed survey of the eastern tropical areas, with a view to finding natural parasites of this scourge. This was the reason for the introduction to Samoa of an entomophyte fungus, Metarrhizum amsopliae, the results of which though not particularly brilliant, were nevertheless quite useful.
This author also mentions trial introductions of the European hedgehog and mole to this area, but makes no comment thereon He also suggests the trial of Scoliid Hymenoptera, from Madagascar * Scoha oryctophaga and Scolia carmfex. His survey was cut short by the war in 1914, just after his arrival in Madagascar.
In 1933, H. W. Simmonds visited Samoa in order to assess the Oryctes situation. He quickly came to the conclusion that it was most urgent to restrict the problem of Co . nt J°l and it was with this in mind that his tour was arranged.
He went to Java, Malaya, Mauritius, Madagascar and Zanzibar, in search of natural parasites which might exist in these territories on the various species of Oryctes larvae Java and Malaya were hardly en
couraging, and tests carried out with the aid of Scolia from these areas were practically negative.
Only one consignment of 122 specimons of a predatory Carabid, Catascopus fascialis WIED, was sent to Samoa.
This research in Mauritius and Madagascar for strains of Scolia oryctophaga ended in the intro duction of 210 females. Un fortunately, the weak multiplication potential of this species—reproduction once a year in Mauritius and Madagascar, compared with twice or three times by the Oryctes in Samoa—is hardly a good omen of its limiting value. However, it is not impossible that some biological regulation or adaptation to equa torial climatic factors may increase the reproduction rate.
As he was leaving Madagascar, Simmonds was told that a species of Scolia had become a parasite of the “Rhinoceros” larvae in Zanzi bar. On his way through, he succeeded in collecting several females which, when tested in a cage, immediately attacked the larvae. Unfortunately, the eggs and larvae obtained did not survive.
This author immediately reported the possibility of the use of this species, but war prevented resump tion of research and it was only in 1945 that a consignment of Scolia ruficornis F. (450 samples) was sent to Samoa. This species has a notable advantage over Scolia oryctophaga in that it develops rapidly (9 days to reach the pupa stage) and probably reproduces several times a year.
According to the Public Relations Office in Fiji (1949), it seems that the introduction of the Zanzibar species has been a success, and Mr.
H. W. Simmonds was informed of this by Mr. D. Eden, general
manager of the New Zealand Reparations Estates. On the other hand, according to Mr. B. A.
O’Connor (letter of April 6, 1950) „ Scolia ruficornis has apparently be come established in one locality in Samoa, taut has not been seen in large numbers. Moreover, there is. no technical service which could undertake the collection and dis patch of this parasite.
Before making any decisions, therefore, it would be necessary to have more definite information on this introduction from the re sponsible quarters. Only the most unequivocal statement could justify the sending of experts to Samoa.
That is the end of the quotation from Mr. Cohic.
Locality Of Asian Beetle
It is now known that the des tructive type of Rhinoceros Beetle {Oryetes ) is spread over Southeast Asia, Malaya and Indonesia, where for a long time it has been attack ing coconut plantations. The history of the pest in the South Pacific may be shown thus: 1909—Brought in rubber plants from Ceylon to Upolu, Western.
Samoa, whence it spread to Savaii and to Tutuila (Eastern Samoa). 1926—Established in Nuitabutabu.
Tonga; but was vigorously attacked, and was eradicated by 1930. 1931—Established in Wallis.
Islands. 1941 Established in Palua section of Micronesia probably spread from Indo-China or Indonesia. 1942- —Apparently established in New Britain and New Guinea, but infestation not officially con firmed. 1950—Established in Vavau.
Tonga. 1953 —Established in Viti Levu.
Fiji. 1953—Campaign in all Territories against the pest being directed and controlled by South Pacific Com mission.