Bess, Henry A.

Nishida, Toshiyuki

Yasumatsu, Keizo

Proceedings of the Hawaiian Entomological Society

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Vol. XX, No, I, June, 1968 239On the Extinction of the Asiatic Rice Borer Chilesuppressalis in Hawaii123Keizo Yasumatsu4, Toshiyuki Nishida5 and Henry A. Bess5INTRODUCTIONThe fate of newly arrived immigrant insects in a new area may beplaced into 1 of 3 categories (1) no establishment, (2) temporary establishment or (3) permanent establishment. Entomologists are concernedwith insects in categories 2 and 3 particularly if they are species of considerable economic importance. The Asiatic rice borer, Chilo suppressalis(Walker), an insect discovered in Hawaii in 1927, may be placed in the2nd category. The purpose of this paper is to present the history of C.suppressalis and to put on record that this borer and some of its importednatural enemies are no longer present in Hawaii. This information willhelp clarify some of the recent literature citations which were true 35years ago, but which are no longer applicable.HISTORICAL BACKGROUNDAccording to the available records Mr. K. A. Ching, Pacific Chemicaland Fertilizer Company, first noticed C. suppressalis in Hawaii during thefall of 1927 (Van Zwaluwenburg et al., 1928). At that time the insectwas known only on Oahu. Four years later Swezey and Van Zwaluwenburg found infestations in rice stubbles on Kauai at Waimea, Hanalei,Kapaa, Wailua, Nawiliwili, Huleia and Hanapepe. (Swezey and VanZwaluwenburg, 1931). Aside from Oahu and Kauai this borer has neverbeen reported from other islands. Judging from its distribution and extentof damage during 1927-1931 the establishment of C. suppressalis in Hawaiiwas not merely an incidental one. According to Van Zwaluwenburget al. the damage was so great that some of the farmers on Oahu stoppedgrowing rice (Van Zwaluwenburg et al., 1928). It was also reported thatin some of the areas of Honouliuli, Oahu the damage was so great thatno rice was harvested.The mode of entry of the borer into Hawaii is not known. It seemslikely that this borer reached Hawaii in rice straw that was being usedContribution Ser. 2, no. 268, Entomological Laboratory, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.Published with the approval of the Director of the Hawaii Agricultural ExperimentStation as Technical Paper no. 902.3This investigation was supported by the U. S.-Japan Binational Cooperative ScienceProgram, National Science Foundation, Grant GF-224; and the Japan Society for the Promotion of Science.'Faculty of Agriculture, Kyushu University, Fukuoka, Japan.5College of Tropical Agriculture, University of Hawaii, Honolulu, Hawaii.table 1. A list of parasites of C. suppressalis in HawaiiSpecies reported Names in current use ReferenceApanteles sp.Amyosoma chilonis ViereckAmyosoma sp.Cremastus hymeniae ViereckCremastus sp.Cremastidea chinensis ViereckCenteterus alternecoloratus CushmanDiodes chilonis CushmanNeotrichogramma japonicum AshmeadNesopimpla narangae AshmeadPhanurus beneficiens (Zentner)Trichogramma japonicum AshmeadT. minutum RileyApanteles chilonis (Munakata)Bracon chinensis SzepligetiunknownTrathala flavo-orbitalis (Cameron)unknownTemelucha biguttulus (Matsumura)no changeEriborus sinicus (Holmgren)Trichogramma japonicum AshmeadItoplectis narangae (Ashmead)Telenomus dignus Gahanno changeno changeVan Zwaluwenburg et al., 1928// // // //Williams, 1931Van Zwaluwenburg et al., 1928Williams, 1931Fullaway, 1931Swezey, 1929Fullaway, 1931Van Zwaluwenburg et al., 192838.oVol. XX, No, I, June, 1968 241as packing material for fragile merchandise shipped from the Orient.Fullaway reported that the larvae of C. suppressalis were found at Honoluludocks in rice straw that was used for packing (Fullaway, 1929). The larvaewere also found in rice straw that was used as packing material for persimmons shipped from Japan to Hawaii by mail. (Whitney, 1931). Becausethe larvae of C. suppressalis may be in diapause for periods as long as 5 to6 months in rice straw they could have easily survived the long ocean voyages between the Orient and Hawaii.Host plants: The records of the host plants of C. suppressalis in Hawaiideserve comment. Besides rice, Oryza sativa L., Kuwana (1929) listed thefollowing host plants from the Orient: Coix lacryma-jobi Linn., Panicummileaceum L. and Zizania aquatica var. latifolia (Turecz.) Komar. In Hawaiiat least 8 plants have been reported as hosts of C. suppressalis. (Van Zwa-luwenburg et al, 1928, Van Zwaluwenburg et al. 1929). In the familyGramineae the following were listed: barnyard grass, Echinochloa crusgallivar. cruspavonis (H. B. K.); rice grass, E. stagnina (Retz.) Beauv.; goosegrass, Eleusine indica (L.); foxtail, Choetochloa verticillata (L.); panicum grass,Panicum barbinode Trin. and Hilo grass, Paspalum conjugatum (Berg.). Otherplants listed were: Eclipta alba (Hassak), family Compositae; and Pha-seolus lathyroides L., family Leguminosae.The question that arises is whether or not these host plants listed fromHawaii were true hosts, i.e., those on which the eggs were laid and in whichthe larvae developed. The present authors believe that the above mentioned plants were not true hosts. It has been observed that in Japanand other countries the larvae of C. suppressalis often crawled out of therice straw at harvest time in the autumn and migrated onto other plants.They have been observed to bore into various plants other than rice duringthis period. Apparently workers in Hawaii were not aware of this habitof the larvae, which is related to the movement into overwintering sites.Parasites: Shortly after the discovery of C. suppressalis in Hawaiiattempts were made to control this borer by the introduction of naturalenemies from China, Japan, and neighboring areas. The parasites introduced are listed in Table 1. According to Dr. C. E. Pemberton (Personalcommunication 1967) these parasites were released only on Oahu and Kauaibecause this borer was found only on these 2 islands.CURRENT INVESTIGATIONSDuring 1963-66 field studies were conducted on C. suppressalis inHawaii. The studies were made initially to locate parasites so that someof the promising species could be sent to Japan. During the course of thesestudies, observations were made on nearly all of the areas in which ricewas currently and formerly grown. These areas are shown in Fig. 2.Rice paddies: The rice industry in Hawaii, which began about 1853lasted about 100 years. From the export and acreage data it appears that242 Proceedings, Hawaiian Entomological Societyzo5 3i-<roQ.Xiu 2%5&j KNOWN TO BE PRESENTX&M UNKNOWN PERIOD2016 ~1850 I860 1890 1930 1940 1950 I9601900 1910 1920YEARSfig. 1. The rise and fall of the Hawaiian rice industry and its relationship to C. sup-pressalis in Hawaii. Data on export from Thrum (1878); those on acreage, Iwai (1927).^>/>;/ aBORER INFESTED AREASI AREAS SUITABLE FOR RICE BUTNOT GROWN DURING OUTBREAKHAWAII 'fig. 2. Map of the Hawaiian Islands showing the rice areas where C. suppressaliswas established. It also shows areas potentially suited for rice culture, but where rice was notgrown on a large scale during the outbreak of C. suppressalis.Vol. XX, No, I, June, 1968 243the industry reached its peak between 1900-1910. From then on therewas a rapid decline. (Fig. 1). In 1962, the writers witnessed what mightbe considered the last rice paddy in Hawaii. This paddy was located atWaialua, Kauai where the Hawaii Agricultural Experiment Station,University of Hawaii, was growing a small area on an experimental basis.Since then the authors have not seen any rice grown in Hawaii.Today only a few remnants of the paddies of the once flourishing riceindustry remain; others have completely disappeared. The former ricelands are now variously utilized, viz., house lots, apartments, fruit orchards,vegetable farms and grazing paddocks. In some areas such as Ewa andHonouliuli, the former rice lands are used for sugar production. The poorlydrained former rice lands in the remote valleys are not being utilized; theyare covered by swamp vegetation.Surveys on stem borer: Extensive surveys were conducted during 1963-66 to determine the present distribution ofC. suppressalis in Hawaii. Sweepings by use of insect nets were made in the vegetation of former rice paddies.Light traps, commonly used in Japan, were also used as a means of determining the presence of C. suppressalis. We were not able to find any mothsat all. The stems of rice and other grasses were carefully examined, butnot a single larva was found.The date of the discovery of C. suppressalis in Hawaii is known; howeverthe time of its disappearance is not known. According to the insect collection at the Hawaiian Sugar Planters' Association and the State of Hawaii,Department of Agriculture, the last specimen of the moth was collected in1939. There are no records of either collections or reports on C. suppressalis since 1939. Thus we know definitely that C. suppressalis was presentin Hawaii during 1927-39. We also know that it disappeared sometimebetween 1939 and 1962.Surveys on parasites: Simultaneously with the surveys on C. suppressalisefforts were made to determine whether or not the parasites introduced forthe control of this borer were present in Hawaii. The areas surveyed werethose areas in which C. suppressalis was known to be present as well as thoseareas that were suitable environments for rice culture. These areas areshown in Fig. 2.During these surveys hymenopterous parasites of various Lepidopterawere obtained, however, not one of the parasites listed in Table 1 wasobserved. Some of the common parasites collected were Chelonus texanus(Cresson), Apanteles trifasciatus Muesebeck, A. marginiventris (Cresson),Meteorus laphygmae Viereck and Opius fletcheri Silvestri6. These were notparasites of C. suppressalis.DISCUSSIONFrom the information obtained from the literature and field surveys6Identifications by Professor C. Watanabe, Hokkaido University, Sapporo, Japan,are gratefully acknowledged.244 Proceedings, Hawaiian Entomological Societyit is possible to come to a few conclusions concerning C. suppressalis inHawaii. It has been stated that C. suppressalis disappeared from Hawaiibecause of the cessation of rice culture. This statement is not true becauserice was grown, albeit in small acreages, up to 1962. It has also been statedthat C. suppressalis caused the downfall of the rice industry in Hawaii.This statement is also not true because, as shown in Fig. 1, C. suppressaliswas discovered in Hawaii after the decline in rice production. What thisinsect did was perhaps hasten the death of the rice industry.According to recent literature, C. suppressalis and its parasites are stillpresent in Hawaii. The present authors conclude that while this statementwas true thirty years ago, it is no longer true. It appears, however, thatsome of the parasites that were not specific to the borer may still be present. For example, Williams (1931) stated that Nesopimpla narangae,Cremastus hymeniae and Trichogramma minutum are also parasites of Omioidesblackburni (Butl.) [= Hedylepta blackburni (Butler)] a moth whose larvaefeed on the leaves of the coconut tree. Presumably these parasites are stillpresent in Hawaii.The cause of the extinction of C. suppressalis has not been established.It is speculated that this borer became extinct because it was not adaptedto conditions of low rice production. It is known that during the years ofhigh rice production in Hawaii 2 crops per year were grown. However,during the years of low production farmers tended to plant 1 crop per year.Under such conditions C. suppressalis was not able to perpetuate itself because the adults live for a few days, and the larvae do not undergo dispauseunder Hawaiian conditions. There was thus a break in its life cycle whichcaused the extinction of the borer.The question of whether or not the plants reported in the literaturewere true hosts was mentioned in this paper. It was pointed out that theplants mentioned in the literature were not true hosts. If they were, C.suppressalis should still be Hawaii because these so called "host plants" arestill in Hawaii.LITERATURE CITEDFullaway, D. T. 1929. Report of the use of straw as a packing material in the Orient.Hawaii Forest. Agric. 26: 81-82.Fullaway, D. T. 1931. Short notes on Hawaiian insects. Proc. Hawaiian Entomol.Soc. 7: 351-365.Iwai, C. K. 1927. The statistical study of rice. Master of Arts thesis. University ofHawaii.Kuwana, S. 1929. Important insect pests of the rice crop in Japan. Proc. 4th PacificSci. Cong. 4: 209-216.Swezey, O. H. 1929. Notes on egg parasites of insects in Hawaii. Proc. HawaiianEntomol. Soc. 7: 282-292.Swezey, O. H. 1929. The hosts of Cremastus hymeniae Viereck in Hawaii. Proc. HawaiianEntomol. Soc. 7: 281.Swezey, O. H. and E. H. Bryan. 1929. Further notes on the insects of Molokai. Proc.Hawaiian Entomol. Soc. 7: 236-237.Vol. XX, No, I, June, 1968 245Swezey, O. H. and R. H. Van Zwaluwenburg. 1931. Notes and exhibitions. Proc.Hawaiian Entomol. Soc. 7: 337.Thrum, T. C. 1878. Hawaiian almanac and annual. Press Pub. Co. Honolulu, Hawaii.(Also volumes for years 1900, 1910, 1920, 1930 consulted)Van Zwaluwenburg, R. H. 1929a. Field hosts of Chilo simplex Butl. Proc. HawaiianEntomol. Soc. 7: 223.Van Zwaluwenburg, R. H. 1929. Notes and exhibitions. Proc. Hawaiian Entomol.Soc. 7: 226Van Zwaluwenburg, R. H., E. W. Rust and J. S. Rosa. 1928. Notes on the rice borerChilo simplex. Hawaii Forest. Agric. 25: 79-82.Van Zwaluwenburg, R. H., E. W. Rust and J. S. Rosa. 1929. Notes and exhibitions.Proc. Hawaiian Entomol. Soc. 7: 218-219.Williams, F. X. 1931. The insects and other invertebrates of Hawaiian sugar canefields. Advertising Publishing Co. Honolulu. 400 pp.Whitney, L. A. 1931. Notes and exhibitions. Proc. Hawaiian Entomol. Soc. 7: 372.ADDENDUMOn October 31, 1968, almost a year after this manuscript was submitted forpublication, Dr. F. Trujillo, Plant Pathologist, Kauai Branch Station, Hawaii Agricultural Experiment Station, noted rice infested with borers at Waialua, Kauai.Investigations made on the following day indicated that the borea was the Asiaticrice borer, Chilo suppressalis (Walker) The identification of the borer was subsequentlyconfirmed by Drs. K. Yasumatsu and K. Yano, Kyushu University, Japan.The discovery of this borer at this time raises some speculative questions. One ofthese is whether the current infestation resulted from the progeny of borers that werediscovered in Kauai in 1929 or whether it resulted from the progeny of a new borerintroduction. No definite answer is available; however, on the basis of the workreported in this paper and other observations, it appears that this is a new introduction.

On the Extinction of the Asiatic Rice Borer Chile suppressalis in Hawaii

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On the Extinction of the Asiatic Rice Borer Chile suppressalis in Hawaii

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