FILE:  <ch-102.htm>                                                                                                                                                        GENERAL INDEX                                    [Navigate to   MAIN MENU ]




Rhabdoscelus obscurus (Boisduval) -- Curculionidae



GO TO ALL:  Bio-Control Cases


Also known as the New Guinea sugarcane weevil, this borer was the second major pest in Hawaii to become the object of biological control (DeBach 1974).  Of south Pacific origin, and probably native to New Guinea and neighboring islands where it probably attacked sago and other palms as well as banana, it became widespread in Hawaii by 1865.  Albert Koebele regarded this beetle as the most injurious pest of sugarcane in Hawaii in 1986 (DeBach 1974).  Before natural enemies were imported, this pest accounted for an annual loss of $750,000 to $1-million.


Foreign exploration for natural enemies began with Dr. F. A. G. Muir of the Hawaiian Sugar Planters Experiment Station with an expedition to southern China in January 1907.  Three years later the project resulted in successful biological control, and is one of the unique odysseys in this kind of work.  Pemberton (1948) relates, "At the time Muir began this adventure there was some published information concerning the borer.  It received its name from specimens collected on New Ireland in 1835.  In 1985 it was recorded from the Island of Larat and by 1895 literature referred to its presence in New Guinea.  It was also known in Tahiti and was supposed to have reached Fiji from Hawaii.  It had also reached North Queensland presumably in cane brought in from New Guinea.  Muir thus had some grounds for suspecting that the native home of this borer was somewhere in New Guinea or the Malay Archipelago to the west.  He began by spending about two months in the Federated Malay States searching for the borer but found none.  He then spent 10 weeks in West Java studying borers allied to the cane borer.  Here he found no true parasites; but a number of predatory insects (Histeridae and Hydrophilidae) were observed feeding on the grubs of these related borers that he found in palms and banana stumps.  He failed to find the sought after cane borer in Java."


"Muir then went to Borneo in July 1907 to undertake similar borer studies.  He failed to find the cane borer; but again found predatory insects similar to those found in Java which fed on other borer grubs occurring in palms and banana stumps.  He remained in Borneo until October 1, 1907 and then returned to Java to ship more of these predatory insects to Honolulu.  These failed.  Having found no promising natural enemy of various borers which he studied in Java and Borneo, Muir decided to move into regions where the cane borer was known to occur and on October 1, 1907 he left Batavia, Java and journeyed some 1,500 miles eastward to the Island of Amboina, where he had reason to believe the borer could be found.  Arriving at Amboina on October 9, he spent 6 weeks searching for the borer in sugar cane, but failed to find it.  He then departed for Larat, a six-day steamer trip to the southeast, where the cane borer had been found by a wandering naturalist in 1885.  Arriving at Larat on November 29, 1907, he soon found the cane borer in sugar cane and in sago-palm stalks and betel-nut palm stems.  A month's study of these revealed no parasites and he returned to Amboina about January 9, 1908.  Having learned at Larat that the borer occurred commonly in sago-palm leaf stalks, he renewed his search for borer parasites on Amboina and was rewarded with success as soon as he visited a sago-palm swamp.  Here he immediately found the borer in the palm-leaf stalks and also discovered that from 25 to 90 percent of the borer grubs were parasitized by a tachinid fly, which was later described and named Ceromasia sphenophori by Dr. J. Villeneuve.  This is the parasite which ultimately checked the borer ravages in Hawaii.  It is now known as Microceromasia sphenophori Vill." [= Lixophaga sphenophori].


"To import this fly from Amboina to Honolulu alive in those days was a disheartening problem.  Transportation was very slow and irregular and all material had to be sent to Macassar, Celebes, thence to Hong Kong and from there transshipped to Honolulu.  Muir remained in Amboina eight months striving in various ways to surmount these difficulties.  Several shipments of the fly were attempted but all failed.  Mr. Terry had been sent out to Hong Kong to receive and send on the consignments from that point to Honolulu.  Muir sent 18 consignments of beneficial insects in all, many of which were histerid beetles which he found preying on borer grubs.  With Terry's aid in handling this material at Hong Kong many of these beetles or their larvae reached Honolulu alive and were liberated in Hawaiian cane fields, but were never seen again.  None of the flies survived the trip.  Finally in September 1908, Muir personally conducted a consignment of the flies from Amboina to Hong Kong, but all died en route."


"Muir then decided to return east to the Island of Ceram to devise other means, if possible, by which the parasite could be introduced into Hawaii.  He had as a companion J. C. Kershaw, who had the year before published and excellent book on the butterflies of Hong Kong.  They worked together in Ceram for a month without success.  Knowing that the cane borer occurred in New Guinea, Muir laid plans to investigate its parasites there, if such could be found.  He returned again to Macassar and obtained transportation to Port Moresby, New Guinea, on April 9, 1909.  Soon after reaching Port Moresby he found the borer in sugar cane some 15 miles inland and immediately discovered the same parasite, which he first found in Amboina.  This he soon attempted to bring to Honolulu alive via Thursday Island and Brisbane, Queensland, but he was forced into a hospital with typhoid fever at Brisbane and his consignment of flies, which was transshipped to Honolulu by a friend, arrived dead.  After 5 weeks hospitalization in Brisbane, Muir returned to Honolulu to recuperate."


"On January 8, 1910, Muir left Honolulu for Queensland to resume his labors on this problem.  During the same month Mr. Kershaw was engaged on the entomology staff.  A relay station for breeding the parasite was established at Mossman, North Queensland, with Kershaw in charge.  Muir then proceeded to Port Moresby again to obtain the parasite.  A mail shipment to Kershaw failed and on April 22, 1910, Muir left Port Moresby for Mossman with a large consignment of parasite material in a living condition.  After unexpected delays and other difficulties he finally reached Mossman with a good lot of living parasites.  The borer being common in cane at Mossman, Kershaw had experienced no difficulty in having three large cages well stocked with borers awaiting Muir's arrival.  This was on May 5.  Some of these parasites were used to stock the cages for the production of a new generation.  Though suffering from an attack of malaria at the time, Muir took the remainder of the parasites and departed for Fiji on the first available steamer.  at Fiji, where the borer was numerous in cane, a cage containing borer-infested cane had been previously prepared by the Colonial Sugar Refining Company to await Muir's arrival.  Upon reaching Fiji, Muir immediately placed the parasites in the cage and then was forced to enter a hospital for treatment and rest because of his malarial condition.  Kershaw reached Fiji from Mossman, Queensland, on August 9 with the remainder of the parasites and by then Muir had sufficiently recovered to depart for Honolulu with Kershaw's cages and the one he had already prepared in Fiji.  Muir arrived at Honolulu August 16 with a good stock of living parasitic material and a month later Kershaw arrived from Fiji with more which he had reared in Fiji from a portion he kept out of the original lot brought by Muir."


These flies were multiplied at the Station in large cages and distributed to the plantations for more than two years, resulting in the establishment of this beneficial insect on all parts of Hawaii where sugar cane was grown, and, during the ensuing years, in the savings of millions of dollars."


DeBach (1974) adds that in order to complete the account of this biological control project, a subsequent change in variety from soft- to hard-rind canes which are not as susceptible to the borer, along with the constant operation of the parasites from New Guinea further reduced the borer to a more negligible level.  However, in the 1960's a return to more susceptible varieties on Kauai again increased borer density.  DeBach (1974) states that this is being reduced by replanting partially resistant varieties. 


For additional details of biological control effort and biologies of host and natural enemies, please also see the following (Illingworth 1914, 1918, 1919; Swezey 1914, Muir & Swezey 1916, Veitch 1921, 1926; Pemberton 1925, Vandenburg 1930, Windred 1936, Wilson 1960, Sabrosky 1967, Long & Hensley 1972).



REFERENCES:   [Additional references may be found at:   MELVYL Library ]



DeBach, P.  1974.  Biological Control by Natural Enemies.  Cambridge University Press, London & New York.  323 p.


Illingworth, J. F.  1914.  Further notes on the breeding of the tachinid fly, parasitic on the cane beetle borer.  J. Econ. Ent. 7:  390-98.


Illingworth, J. F.  1918.  Tachinid parasite of the cane borer beetle.  Queensland Agric. J. 10:  149-50.


Illingworth, J. F.  1919.  The sugar cane beetle borer parasite (Ceromasia sphenophori) in Queensland.  J. Econ. Ent. 12:  457-59.


Long, W. H. & S. D. Hensley.  1972.  Insect pests of sugar cane.  Ann. Rev. Ent. 17:  149-76.


Muir, F. & O. H. Swezey.  1916.  The cane borer beetle in Hawaii and its control by natural enemies.  Hawaii. Sugar Planters' Expt. Sta. Ent. Ser. Bull. 13:  3-51.


Pemberton, C. E.  1925.  A study of the cane borer, Rh. obscura and its parasite C. sphenophori at Paau-hau Sugar Plantation Company, Hawaii.  Hawaii. Planters' Rec. 29:  174-85.


Pemberton, C. E.  1948.  History of the Entomology Department Experiment Station.  HSPA 1904-45.  Hawaiian Planters Record 52(1):  53-90.


Sabrosky, C. W.  1967.  Corrections to a Catalogue of the Diptera of America North of Mexico.  Ent. Soc. Amer. Bull. 13:  115-25.


Swezey, O. H.  1914.  The introduction of a tachinid parasite of the sugarcane weevil borer in Hawaii.  J. Econ. Ent. 7:  455-57.


Vandenberg, S. R.  1930.  Report of the entomologist.  Guam Agric. Expt. Sta. Rept. 1928:  23-31.


Veitch, R.  1921.  The partial success of the tachinid parasite of the sugarcane beetle borer.  Fiji. Dept. Agric. Agric. Cir. 2:  46-7.


Veitch, R.  1926.  Notes on some attempts to control Fijiian plantation pests by the introduction of parasites and predators.  Pan-Pacific Sci. Cong. Proc. (1923) 1:  377-83.


Wilson, F.  1960.  A review of the biological control of insects and weeds in Australia and Australian New Guinea.  Commonwealth Inst. Biol. Control, Tech. Commun. 1.  102 p.


Windred, G. L.  1936.  Investigations on the cane beetle borer, Rhabdocnemis obscure Boisd., and its parasite, Ceromasia sphenophori Vill., in Fiji.  Internatl. Soc. Sugar Cane Technol. Proc. 1935:  358-78.