Poinar, George O.

Proceedings of the Hawaiian Entomological Society

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Vol. XVIII, No. 3, June, 1964 417Observations on Nutgrass Insects in Hawaii with Notes onthe Host Range of Bactra truculenta Meyrick andAthesapeuta cyperi MarshallGeorge O. Poinar, Jr.1DEPARTMENT OF BIOLOGICAL CONTROLUNIVERSITY OF CALIFORNIA CITRUS RESEARCH CENTERAND AGRICULTURE EXPERIMENT STATIONRIVERSIDE{Submittedfor publication October, 1963)INTRODUCTIONThroughout many parts of the world, the purple nutgrass, Cyperus rotundus L.,is regarded as a troublesome weed and often as an important pest. A closelyrelated species, C. esculentus L., frequently called yellow nutgrass or chufa, is alsooften classified as a weed, although in certain areas it is a source of food forwildfowl, livestock and occasionally even for humans.Both species are believed to have originated in the Mediterranean region, andvarious control practices have been employed throughout the world for theirdestruction. Because of its more durable rhizome system, purple nutgrass hasresisted both cultural and chemical control measures in many areas and has beeninvestigated for possibilities of eradication by means of biological control.Hawaiian scientists were the first to attempt this when they studied insect pestsof nutgrass in the Philippines and introduced two insects from that country intoHawaii in 1925 to combat C. rotundus (Swezey 1926, Pemberton 1948).These two insects were Bactra truculenta Meyrick (Olethreutidae) and Athesapeuta cyperi Marshall (Curculionidae) which soon became established on Oahuand spread to the islands of Hawaii and Maui. Initially, the moth seemed mostpromising (Swezey, 1927-1928), but eventually native parasites reduced itseffectiveness (Swezey 1931, 1935, 1946). The weevil was somewhat slower inspreading, but now, at least on several of the islands, has a range equal to thatof B. truculenta (Swezey and Pemberton, 1931).The author spent three and one-half months (April 15-July 31, 1963) on theisland of Hawaii studying the host range of B. truculenta and A. cyperi to determineif introductions into southern California for biological control of nutgrass wouldbe safe. During these studies, there was ample opportunity to examine the insectfauna of both C. rotundus and C. esculentus.1 Grateful acknowledgement is made to Clifton J. Davis and Ernest R. Yoshioka, whosupplied laboratory space and facilities for these studies at Hilo, Hawaii, and to F. A. Bianchi,N. L. H. Krauss, and J. W. Beardsley, whose help in locating available literature on the floraand fauna of the islands is deeply appreciated.418 Proceedings, Hawaiian Entomological SocietyBACTRA TRUCULENTA MEYRICKLife history studies: This olethreutid was first described by Meyrick fromIndia (1909). It is also recorded from the Philippines and Burma and maypossibly occur in South America (Williams, 1931). Both Ghosh (1921) andWilliams (1931) have published brief accounts on the biology of this moth andfurther findings by the author follow below.The eggs, laid either in the midrib groove or on the smooth surface of thenutgrass leaf, are flattened and usually overlapping in a row. Several hundredeggs were held at an average temperature of 74.2° F. (range of 65.6-82.8)over a two-week period and found to hatch in Rye and one-half to six days at anelevation of 75 feet.The eggs are white when first laid, and the embryo can be distinguished aftertwo to three days. The eyes are visible after three to four days and the internalorgans in five to six days. At the time of hatch, the larva is pale yellow with ablack prothoracic shield and head capsule.Just before emergence from the egg, the larva initiates biting motions againstthe chorion. As this behavior becomes more intensified, the head is swung backand forth as the larva searches for other possible emergence areas. Eventually, thechorion is broken and the larva makes its exit.After emergence, many larvae crawl a short distance away from the egg,burrow into the leaf and tunnel toward the base of the plant. They may lateremerge from the leaf and start a new tunnel or simply crawl over the plant andeventually make their way down to the base of the stem where they tunneldirectly into the stem tissue. A few of the larvae drop off the leaves, suspendedby a delicate silk strand, and are blown to neighboring plants.After entering the plant, the larvae make their way to the meristematic stemtissue and some eventually reach the bulb and feed on its contents. The first signof infestation is the yellowing of the inner leaves of the plant as they are severedfrom the main portion of the stem. These leaves wither and die and usually thewhole plant eventually succumbs. Sometimes an adventitious shoot is sent upfrom the base of the plant which survives after the parent plant dies.Under laboratory conditions, the larval period lasted from 18 to 20 days at anaverage temperature of 75° F. The pupa was formed in a lightly constructedcocoon in the basal stem portion of the plant. The adult moth emerged in abouta week and was capable of ovipositing in about two days. Two females that werereared from larvae were caged until death and found to have laid 77 and 130 eggs,respectively.Parasites: The gradual lack of effectiveness oiBactra on nutgrass in succeedingyears after its introduction was generally attributed to parasitization of the eggsby Trichogramma minutum (Swezey 1931, 1931a, 1946). The author found eggclusters of Bactra which ranged from 0 to 100 percent parasitized by T. minutum.Parasitized eggs appear totally black to the naked eye, in contrast to the yellowcolor of unparasitized eggs. This color appears to be due to a darkening of theinside of the chorion and not to the body of the parasite itself.The only other recorded parasite of B. truculenta appears to be Chelonusblackburni Cameron (Braconidae) which was recorded from one larva on the-Vol. XVIII, No. 3, June, 1964 419island of Maui (Swezey 1929). However, I discovered that during May and Junemany of the moth larvae feeding on yellow nutgrass in the sugar plantations were^--parasitized by two ichneumonids, Diadema blackburni (Cameron) and Eriborus sp.2Each is a larval parasite which emerges from the body of the caterpillar after ithas spun its cocoon and then forms its own cocoon inside the Bactra cocoon.Host plant studies: Very little information is available concerning the hostrange of Bactra tmculenta. Pemberton (1948) mentions that tests were made withthis moth in Honolulu in 1922 on economic plants, but I have been unable tofind any account of these experiments.According to all previous records, it appeared that B. truculenta was confinedto Cyperus rotundus and substantiating this was the report that it had never beenrecorded injuring any crop or garden plant in India or the Philippines (Swezey,1926). Since its introduction into Hawaii, however, it has been discovered feedingon Kyllingia monocephala Rottb. (Swezey 1929) and K. pumila Michaux (Williams,1931).In order to insure that this insect would not harm other plants if introducedinto California, host plants studies were conducted with plants in the Gramineae,Cyperaceae, and Juncaceae.The results are shown in table 1. In the oviposition studies, 10 to 15 adultmoths were caged with the host plant. In the larval feeding tests, newly hatchedlarvae were placed both on and in potted and cut plants.Results indicate that the adults will oviposit on a wide variety of plants;however, the feeding habits of the young larvae are much more restricted andof the plants tested, development can be completed only on C. rotundus, C.esculentus, C. alternifolius L. and C. papyrus L. Only a few larvae were able to complete their development on the latter two plants, and the pupae were all destroyedby ants before they could mature. I have been unable to locate infested plants ofC. papyrus and C. alternifolius in the field, but Bactra larvae are quite common inesculentus. In order to determine if Bactra adults showed any preference in regardto oviposition on various host plants, a number of potted plants were trimmedto about the same surface area of foliage and placed in a large screen cage with20 adult moths.After 4 days, the plants were removed and examined for eggs. The numberof eggs laid on each plant is as follows:CyperusrotundusL 37Sorghum halepense (L.) Pers 29Cyperus esculentusL 17Cyperus alternifolius L 17Avena sativa L 9Tropaeolum majus L. (nasturtium) 0The results indicate that the adults do show a preference, yet plants other thanthe desired host (C. rotundus) are also chosen for oviposition.The first instar of Bactra truculenta was unable to live on any of the other sedgesand the rushes and grasses tested. When later instars were placed on corn, wheat,and oats, they fed for a day or two and then succumbed.2 Determined by Dr. L. M. Walkley, Entomology Research Division, Beltsville, Maryland.420 Proceedings, Hawaiian Entomological SocietyATHESAPEUTA CYPERI MARSHALLLife history studies: This barine was described by Marshall in 1928 and isknown to occur only in the Philippines. Close relatives are found in India(Marshall, 1928) and Burma (Ghosh, 1921).Table. 1. Results of Host Plant Studies for Ovipositional Sites and LarvalFeeding of Bactra truculenta MeyrickHost PlantsGramineaeAvena sativa LTriticum vulgare VillBromus unioloides H.B.KSorghum halepense (L.) PersZea mays LFestuca elatior LPoa annua LHordeum vulgare LLolium perenne LDactyles glomerata LCyperaceaeCyperus esculentus LC alternifolius LC. papyrus LCarex wahuensis C. A. Meyervar. rubiginosa R. KraussEleocharis obtusa SchultesScirpus lacustris LFimbristylis polymorpha BoeckelerKillingia pumtla MichauxJuncaceaeLuzula campestris (L.)DC. var. hawatiensis (Buch.)Degener and FosbergJuncus bufonius LEggs Deposited++OOOO+++++I ++ ++Larvae Fed(first instar)II+1111IlllllllllDevelopmentCompleted++Plant died0=not tested+ =yesAs with most of the weevils of this tribe, little of their biology is known. Thefollowing observations will supplement Williams' notes (1931) on the biologyof this weevil.Adults were kept in petri dishes and a fresh portion of the nutlet, stem, andlower portion of nutgrass leaves was supplied every other day. Eggs weredeposited in cavities in the tubers of the plants. They were about one-fourth mm.long, pearly white when laid, and remained so except for the head capsule whichturned black just before hatching. The incubation period lasted four to five daysat an average temperature of 75° F.The young larvae apparently enter the base of the stem and make their way tothe meristematic tissue and down into the tuber where they feed on its contents.Vol. XVIII, No. 3, June, 1964 421Pupation occurs in the hollowed-out tuber, and the adult is formed after 10 to 11days (at average temperature of 75° F.). The newly formed adults seem to spenddays inside the tuber before making their way to the outside.In the field during the day, the adults could be found in the soil, hiddenbetween the bases of the leaves, or rarely exposed on the leaf surface. In thelaboratory, they fed on all parts of the plant but preferred the basal stem portionand the nutlet. The adults appear to have a preoviposition period which maylast up to two months or longer. Mating was observed one month after emergence,but oviposition occurred much later. No parasites of the weevil were recovered.Host plant studies: Because of the long preoviposition period of the nutgrassweevil, there was no opportunity to test various plants for oviposition sites anddetermine the host range for the early larval instars.Instead, adults were placed on various plants and third and fourth larvalinstars were transferred from nutgrass stems obtained in the field and placed onstems of various test plants in the laboratory.The results are shown in table 2. In the laboratory, the adults fed only onTable 2. Results of Host Plant Tests with Adults' and Older Larvae of Athesa-peuta cyperi MarshallHost PlantsGramineaeAvena sativa LTriticum vulgare VillZea mays LTriticum vulgare VillCyperaceaeCyperus papyrus LC. esculentus LC. alternifolius LCarex wahuensis Meyervar. rubiginosa Krauss.JuncaceaeJuticus bufonius LOtherBidens spTropaeolum majus L.(Nasturtium)Coreopsis spLarvalStage3rd3rd4th4th4th3rd4th3rd and 4thLarvaeFed0000DevelopmentCompletedAdultFedII1o++o1o10 = not tested+ =yes-=noC. esculentus L. and C papyrus L. The data gained from the larval trials suggestthat, as with the moth, later larval instars can complete the remainder of theirdevelopment on a wider range of plants than can the first instars.In the field, C. esculentus was heavily attacked and appears as acceptable to theweevils as C. rotundus. Larvae were also found in C. polystachyos Rottb., and anadult was observed feeding on K. pumila.422 Proceedings, Hawaiian Entomological SocietyFIELD OBSERVATIONSIn general, both insects appear to be more plentiful at the lower elevations inHawaii although the weevil has been recorded as high as 3,000 feet on Oahu(Zimmerman, 1936).Both the moth and the weevil are often found in the same locality and althoughthey may occur side by side, have never been found together in one plant. In fact,I have never found more than one of these insects in a single nutgrass plant.In plants of C. esculentus in the sugarcane field on Hawaii, the weevil appearedmore abundant than the moth in May, and out of 25 plants examined, six wereinfested with the weevil and three with the moth. This may be due to parasitiza-tion of the moth, however.In a macadamia nut orchard infested with C. rotundus, the moths were muchmore plentiful than the weevil and continued breeding throughout the summermonths. It is difficult to say what factors play the leading role in the abundanceof these two insects. The extremes of temperature and moisture found in Hawaiioffer a good chance to study the effect of physical factors on the distribution ofthese insects.REPORTS OF HAWAIIAN NUTGRASS INSECTSA number of other insects have been reported feeding on C. rotundus in Hawaiiat one time or another and will be briefly discussed below. Most of these are notspecific to nutgrass.Two species of mealybugs, Dysmicoccus brevipes (Cockerell) and Geococcus radicumGreen have been reported on the roots of nutgrass, C. rotundus, in the HawaiianIslands. Both also attack pineapple.Two species of thrips, Taeniothrips cypraceae Bianchi and Haplothrips (Hindsi-ana) sakimurai Moulton have also been reported attacking C. rotundus in Hawaii.Both are found on other plants.The aphid Schizaphis cyperi (Van der Goot) was first found in the HawaiianIslands in 1939 and feeds on the above-ground portion of C. rotundus L. (Zimmerman, 1948).Several species of Lepidoptera have been reported feeding on C. rotundus inHawaii. These are Spodoptera mauritia Boisduval3 (Williams, 1931), Spodopteraexempta (Zimmerman, 1958), and Pseudaletia unipuncta (Zimmerman, 1958).Beardsley (1963) noted adults of Sphenophorus cariosus (Olivier) around theroots of nutgrass, C. rotundus, and observed adults feeding and ovipositing onthis plant under laboratory conditions.Insects associated with Nutgrass in HawaiiDuring this study in the summer of 1963, I came across the following insectsassociated with nutgrass. The aphid, Schizaphis cyperi, was collected on C. rotundusbehind the laboratory in Hilo, Hawaii. Its occurrence seems to depend on theactivity of ants which distribute the aphids from plant to plant. Most of theaphids were clustered on the basal stem portion of the plant.3 Owing to a misidentification, Hawaiian records of S. mauritia prior to 1938 should applyto S. exempta (see Proceedings 10:75, 1938).Vol. XVIII, No. 3, June, 1964 423Rhopalosiphum rufiabdominalis (Sasaki)4 is a very common aphid found on rootsof Cyperus esculentus in cane fields. Individuals of all sizes can be found on rootclusters just beneath the tuber, and they are frequently attacked by coccinellidTafvae. Their feeding often causes a general chlorotic condition of the plant.In one field, out of 50 plants of C. esculentus, 31 were infested with this aphid.Taeniothrips cyperi was common in the basal portion of the leaves in bothC. rotundus and C. esculentus. When in large numbers, their feeding produces ascarring effect on the leaves which then show a purplish cast.Specimens of Dysmicoccus brevipes (Cockerell)5 were feeding on the tubers ofboth C. rotundus and C. esculentus. Saissetia nigra (Nietner)5 was found on leavesof many C. rotundus plants at Hilo during July. Several specimens of Chorizococcus(=Trionymus) rostellum (Hoke)5 were discovered on the roots of C. esculentus atHilo, also during July.LITERATURE CITEDBeardsley, J. W. 1963. Billbugs on Nutgrass. Coop. Econ. Insect Rept. USDA. 13(10) :186.Bianchi, F. A. 1945. Notes on Hawaiian Thysanoptera with Description of a New Species.Proc. Hawaiian Ent. Soc. 12(2):279-286.Ghosh, C. C. 1921. Supplementary Observations on Borers in Sugarcane, Rice, etc. Rept.Proc. Fourth Entomological Meeting at Pusa, 105-136.Marshall, Guy A. K. 1928. New Injurious Curculionidae. Bull. Ent, Research 18(3):257-266, 5 figs.Meyrick, E. 1909. Descriptions of Indian Micro-Lepidoptera. X Eucosmidae. Jour. BombayNat. Hist. Soc. XIX, 3:582-607.Pemberton, C. E. 1948. Nutgrass Insects. Hawaiian Planters' Rec. 52(l):78-79-Swezey, O. H. 1926. Recent Introductions of Beneficial Insects in Hawaii. Jour. Econ.Ent. 19(5):7l4-720.Swezey, O. H. 1927-28. Entomology. Report Comm. Expt. Sta. Hawaiian Sugar PlantersAssociation. 19 and 16-17.Swezey, O. H. 1929. Nutgrass Borer {Bactratruculenta). Report Comm. Expt. Sta. HawaiianSugar Planters' Association. 18-19.Swezey, O. H. 1931. Nutgrass Borer {Bactratruculenta) Proc. of the Fiftieth Annual Meetingof the Hawaiian Sugar Planters' Assn. p. 427.Swezey, O. H. 1931a. Proc. of the Fiftieth Annual Meeting of the Hawaiian Sugar Planters'Association, p. 125.Swezey, O. H. 1935. Note. Proc. Hawaiian Ent. Soc. 9(1):32.Swezey, O. H. 1946. Note. Ibid. 12(3):475.Swezey, O. H. and Pemberton, C. E. 1931. Nutgrass Insects. Report Comm. Expt. Sta.,Hawaiian Sugar Planters' Assn. p. 23.Williams, Francis X. 1931. Handbook of the Insects and other Invertebrates ofHawaiian Sugar Cane Fields, p. 400. Hawaiian Sugar Planters' Assoc, Honolulu.Zimmerman, E. C. 1936. Note. Proc. Hawaiian Ent. Soc. 9(2): 116.Zimmerman, E. C. 1948. Insects of Hawaii 2:414, 445. Univ. of Hawaii Press, Honolulu.Zimmerman, E. C. 1948a. Insects of Hawaii 5:100. Univ. of Hawaii Press, Honolulu.Zimmerman, E. C. 1958. Insects of Hawaii 7:305, 336. Univ. of Hawaii Press, Honolulu.4 Determined by L. M. Russell, Entomology Research Division, Beltsville, Maryland.5 Determined by J. W. Beardsley, University of Hawaii, Honolulu.

Observations on Nutgrass Insects in Hawaii with Notes on the Host Range of Bactra truculenta Meyrick and Athesapeuta cyperi Marshall

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Observations on Nutgrass Insects in Hawaii with Notes on the Host Range of Bactra truculenta Meyrick and Athesapeuta cyperi Marshall

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