l99rl HALFPAPPAND STOREY:CANE WEEVIL BORER

Prinripes.35(4).1991. pp.199 207

Cane Weevil Borer. Rhabdoscelusobscurus (Coleoptera:Curculionidae), a Pest of Palms in Northern Queensland,Australia

K. H. HerrpAPP ANDR. I. Sronrv Department of Prinary Industries, P.O. Box 1O54, Mareeba, QId, 4880

AssrRecr land. Somebadly infestedfields in the South Johnstonedistrict had one in three stalks In recent years the cultivation of ornamental palms (Arecaceae) has increased markedly in northern affected,with populationsof over 250,000 Queensland. Consequently, several insects have larvae per hectare (Mungomery 1953). become important pests, particularly Rhabdoscelus Mungomery (1953) believed that R. obscurus (Boisduval),the cane weevil borer. The lar- obscurusonly reached its current negli- vae of this beetle feed on various species of palms, gible pest statusin the sugar industry when making the plants unsaleable.Death or lodging of the trees may also result. This paper documents its pest preharvest burning of the crop became status. derived from information in the literature and almost universal. This practice destroved from consultation with local growers. most emerging adults and milling kiiled most larvae and pupae. Although Rhabdoscelus obscurus The first enquiry we received about .lt. (Boisduval), the cane weevil borer, was obscurusas a pest of palms in northern originally describedfrom New Ireland the was related to an attack on original range of the speciesis unknown. Queensland coconutpalm in Cairnsin 1977. Sincethat Zimmerman (1968) believed thai R. time reports have gradually increased,with obscurus was probably native to the Pa- a large number being received over the puan area, and has since spread, its cur- last two years. Alihough this undoubtedly rent distribution ranging from the Celebes reflects an increasedinterest in growing in Indonesia through New Guinea, south palms in the area, long term enthusiasts and east to Polynesia, and Queensland, interviewed believed that there was a def- Micronesia and north to Hawaii. Its spread inite increase in weevil activity over the is almost certainly associated with the last 2 to 3 years.The purposeofthis paper transport of sugar cane by man. is to provide an information base on this Mungomery (1953) was of the opinion weevil and its importance to northern that R. obscurus first entered Queensland palm growers and to discuss in infested sugar cane directly from New Queensland the need or otherwise for further studies. Guinea about 1896. Jarvis (1927) stated that it was first noticed in the Mossman Life History and Johnstone River districts in 1907, spreadingrapidly as far south as Mackay Most literature on the life history of R. through unrestricted movement of seed obscurus relates to sugar cane, especially canebetween mill areas.By the mid 1930's from Hawaii where the weevil is still a R. obscuruswassecond only to canebeetle major pest. The following information is (Scarabaeidae:Lepidiota spp. and other largelyfrom Napompethet al. (1972). The genera)as a pest of sugar cane in Queens- adult female chews a cavity about 3 mm PRINCIPES lvor. 35 deep in the sugar cane stalk, usually in fall over and die. Damage mostly occurs adult feeding scars or cracks, sometimes up to I meter above the ground. at internodes or in leaf sheaths. A single egg is then laid, which hatchesin 3-7 days OverseasHosts (mean 4.6). The developinglarva (Fig. 2) R. is consideredto be pri- feedson the pith (not the fibers),tunnelling obscurus marily a cane, although Muir up and down the stalk, occasionallybreak- pest of sugar Swezey(1916) believedthat the orig- ing through to the surface leaving char- .and inal hosts were likely to have been palms acteristic windows.The larval stage,which and Napompeth et al. (1972) hasabout 6 instars,Iasts from 45-61 days bananas. Rauenala madagas- (mean 54.3). It then enters a prepupal listed corn, papaya, cariensis F. Gmel.(traveller's tree) and stage of about 7 days, finally pupating in J. Strelitzia reginae Banks (Birds-of-para- a cocoon made of a spirally woven mass as alternate hosts and Zimmerman of frbersand frass. After I7 -25 davs(mean dise) (1968) listed maize and other grasses, 2l) the adultsemerge. Adult beeiles(Fig. Erianthus spp. and Inocarpus l) are variable in color, with about 6 dis- "f"Stf", (Parkinson)Fosb. (as edulis & G. tinct patterns of light and dark markings. J. R. Each adult weevil is 10.0 + 3.0 mm in Forster). (1972) length and 3.5 + 1.1 mm in width, while Napompethet al. listed the fol- weightvaries from 2 I .3- I I8.2 mg (mean Iowing palms as hosts: Archontophoenix 66.1 in males, 67.8 in females).Adults alexandrae-alexandra pahn; Areca cat- are long lived, surviving up to 70 months echu-berel-nttt pahn; Caryota ur ens L.- wine palm; Cocosnucifera-coconut palm; furcaptivity, but probably less in the wild. Beetlesfly infrequently and are most active Metroxylon sagz Rottboel-sago palm; Pritchardia martii (Gaud.) H. A. around dawn and especially dusk. Van Wendl.-loulu palm; Ptychosperrna ele- Zwaluwenburgand Rosa(1940) found that Roystonea R. obscurus can move considerabledis- g'ans-solitaire palm; elata (Bart.) tances (mainly by flight), marked and Harper-royal palm; Sabal pal- metto (WaIter) Lodd. ex A. & H. releasedspecimens being taken up to 0.5 J. J. Schultes-cabbage palm. Lever (1969) km from releasesites. They concludedthat alsolisted Areca catechu wind was probably the main environmental Cocosnucifera, and.Metroxylon spp. as hosts. influence on field movement and that most infestationsin new fields came from adja- cent fields, rather than carrying over from AustralianHosts crop to crop. One female can lay up to The majority of available records in 176 eggs,90% of which are laid in the Australia are for sugar cane. Mungomery (laboratory first 25 weeks conditions).Eggs ( I 937) statedthat he knew of no authentic are not laid continuouslybut in short peri- record of R. obscurasfeeding on bananas ods of activity. in He did record Archonto- (1979) Queensland. Dharmarajuet al. discussedthe phoenix a,lexa,ndraeas a host,the cocoons weevil'slife history in coconut palms. Eggs being present in felled wild trees. are laid in the epidermis of 4=6 year old trees. Up to severalhundred larvae were NaturalEnemies found developing within the trunk of a single tree. Pink sap which exudes from A tachinidparasite of R. obscurus,Li*,- wounds attracts other adults. Cocoonsare ophaga sphenophori (Villeneuve) was found inside the tmnk, the weevilsleaving successfullyintroduced from Papua New exit holes as they emerge. Heavy infes- Guineaby Jarvis, working with the Hawai tations weakenthe trunk and the tree may ians,Muir and Kershaw,in I910. By l9lB leerl HALFPAPPAND STOREY:CANE WEEVIL BORER 201

I. Adult Rhabdoscelusobscurus. 2. Mature larva of R. obscurus in trunk of young Archontophoenix alexandrae. 3. Damaged trunk of Archontophoenix alexandrae. Note jellyJike exudate from R. obscurus feeding hole. 4. Damage to potted Archontophoenix alexandrae by R- obscurus. PRINCIPES [Vor. 35 it waswell establishedin the Mossmanarea against C. sordidus. Like the histerid Plne- and was then reared in numbers at the sius jaaanus it failed to establish. Zim- Meringa laboratoriesof the Bureauof Sugar merman (1968) lists the elaterid, Conode- "various Experiment Stations and widely released rus exuL(Sharp) and ants,mites, between Proserpine and Cairns. Although firngi and some other predators and par- it was still present as late as 1952, Mun- asites" as affecting R. obscurus numbers. gomery (1952) statedthat parasitismrates Other agents are also recorded as par- rarely exceeded 5% which he attributed asitesor predators of R. obscurzs, includ- to the removal of available hosts by the ing rats which will eat the cocoons and yearly harvest. Wilson (1960) however, Bufo marinu.s L., the cane toad, which noted that L. sphenophori did exercise a commonly preys on R. obscuras adults high degreeof control of R. obscuruswhere (Wilson 1960). Wilson (1960) also conditions were favorable, such as the reported that the green muscardinefungus Tully-Mossman area. Metarrhiziurn anisopliae attacks R. In addition to L. sphenophori, Muir & obscurus in Queenslandand that the spe- Swezey(1916) (except where indicated) cies was consideredfor biological control listed the following as natural enemies of n 1923-24. He also reported the intro- R. obscurus: duction of an unspecified entomogenous Plaesius jaaanus Erichson (HISTER- fungus from the Philippines in 1928. h IDAE)-Larvae and adults of this large was then cultured on media and transmit- beetlelive inside weevil infested palms and ted to R. obscurus, but no further infor- bananas,feeding on weevil adults and lar- mation is available on its successor oth- vae, especially on Cosrnopolites and. erwise. Sphenophoru.s(other weevil generarelated R. in P. jauanus to obscurus) bananas. The CurrentSuruey was releasedin Cooran, southeastQueens- land to control Cosmopolites sord.idus Twenty-two growers were interviewed (Germar),the bananaweevil borer, in 1928 and their nurseriesexamined in late 1989 (Weddell L932). One Plaesiu,slarva can with regard to R. obscurus.For each nurs- consume up to 34 weevil larvae per day, ery, notes were taken on size of plantings, anadult averaging B per day. Waterhouse establishmentdates, range of palm species and Norris (1987) stated that despite sev- grown, and microhabitat. With respect to eral attempts to introduce this speciesinto R. obscurus.data were obtainedon amount southeast Queensland and New South and type of damage,palm speciesaffected, Wales from both Java and Fiji (where it age and situation (potted or field planted) had been successfullyintroduced), it failed of palms attacked, weather or seasonal to become established. effects noted by grower, and any control Platysoma abruptum Erichson (HIS- measuresemployed. These growers ranged TERIDAE)-This speciesis similar to P. from enthusiasts with an interest in palms, jaoanus but smaller. to commercial seedlingssuppliers and pro- Simodactylus sp. (ELATERIDAE)- ducers of larger plants for landscaping. Larvae feed on R. obscurus in palms, Large scale growers had trees in pots or especiallythe pupal stage. in the field numbering several hundred Chrysopilus sp. (RHAGIONIDAE)- thousandplants. The area coveredextends Larvae of these flies feed on beetle and from Cape Tribulation (I00 km north of other fly larvae in palms and bananas. Cairns) south to Bramston Beach on the Waterhouse and Norris (1987) noted the coast,plus Kuranda and Julatten at higher introduction into Australia in l92B of altitudes (300-400 m) on the Atherton Chrysopilus ferruginosus Wiedemann Tableland.(see Fig. 7). All but five of these l99ll HALFPAPPAND STOREY:CANE WEEVIL BORER

5. Damage by R. obsurus to trunk of Wodyetia bifurcata. Note cracking. 6. Damage to trunk of Chrysali- docarpus mad,agascariensisby R. obscurus.Note exudate from feeding hole and subsequentstaining.

had weevil problems ranging from mild to This could indicate that there are two gen- severe. The five negative cases included erations per year and this possibility was some very recently established plots or supportedby larval sizesencountered dur- those using heavy chemical control pro- ing the survey-either large or very small, grams which apparently kept the weevils with no intermediates.The dry seasonpeak in check. The climate is tropical monsoonal alsocoincides with the period of sugar cane with hot wet summersand warm dry win- harvest in northern Queensland,and bee- ters. tles could be moving into palms as this host Palm plantationsare grown in a variety disappears. Growers believed that beetle of habitat types ranging from rainforest to activity was not influenced by short term Melaleuca or Eucalyptus open forest, with weather patterns, but long term effects several on former sugar cane land. There such as a seriesof wet or dry years could appearsto be no correlation betweenwee- be expected to affect weevil numbers. vil activity and habitat type, all areasbeing Table I lists the speciesof palms found equally susceptible. to be hostsof R. obscurusat the time of R. obscurus is active throughout the the survey. Although most records were year in the region, although several grow- confirmed by the senior author, a few are ers believed there was increased activity speciesnoted by growers as susceptibleto in the wetter summer months. Others also attack. However, as adult and larval stages believedthere was an increasein activity of the insect and its damage are quite in the dry late winter,/early spring period. distinctive,the grower recordsare accepted 204 PRINCIPES [Vor. 35

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7. Map of study area with place names used in text. as valid. The most susceptible hosts are Metroxylon. At the Port Douglas site, 36 Carpentaria, Chrysa.lid,ocarpus,Roysto- weevil pupal.cells were closely examined nea alnd Wodyetia. However, this could for fly pupae. Of these, 2l were found to reflect the palms most popular with grow- be parasitizedoeach weevil pupal cell con- ers. One long'term palrn grower was of the taining I-7 fly pupae, with a mean of 2.4 opinion that there were few palms that R. fly pupae per parasitizedweevil pupa. This obscurus would not attack. high parasitism rate contrasts with the sit- The tachinid parasite Lixophaga uation in weevil infested sugar cane where sphenophori ryasfound to be active at two the parasiteis rarely encountered,possibly coastal sites, one at Port Douglas and the due to low host numbers and the unsuit- other at Cape Tribulation, Adult flies ability of sugar cane fields for survival and emerged from R. obscurus pupal cells in developmentof the fly (K. Chandler, pers. Carpentaria, Chrysalidocar.pus and comm.). The beetles Dactylosternum l99rl HALFPAPPAND STOREY:CANE WEEVIL BORER 205

Table 1. Palrn hosts o/Rhabdoscelusobscurus (BoisduuaQ in northern Queensland.

Native (N) or Exotic Species Common name (E)

Coryphoideae Licuala spp. Licuala Palms E Phoenix canariensis Hort. ex Chabaud Canary Island Date Palm E Calamoideae +Metroxylon salomonense(Warb.) Becc. Solomon Sago Palm E *Pigafetta f.larls (Giseke)Becc. Pigafetta Palm E Ceroxyloideae *Hyophorbe lagenicaulis (L. H. Bailey) H. E. Moore Bottle Palm Arecoideae Caryota mitis Low. Clustered Fishtail Palm E * Chrysalidocar pus madagascariensis Becc. Green Cane Palm E *Chrysalidocarpus lutescens H. A. Wendl. Golden Cane Palm E *Neodypsis decaryi H. ltnelle Triangle Palm E Phloga nodifera Noronha ex. Salomon E Dypsis sp. Dypsis Palms E Euterpe spp. Assari Palms E *Roystonea regia (Kunth) O. F. Cook Cuban Royal Palm E *Archontophoenix alexandrae (F. v. Mueller) H. A. Wendl. & Drude Alexandra Palm N * Archontophoenix cunninghamiana (H. A. Wendl.) H. A. Wendl. & Drude Bangalow Palm N *Carpentaria acuminata (H. A. Wendl. & Drude) Becc. Capentaria Palm N

*Normanbya normanbyi (W. HilD L. H. Bailey Black Palm N *Wodyetia bifurcata A. K. Irvine Foxtail Palm N *Ptychosperma elegans (R. Br.) Blume Solitaire Palm N *Areca catechu Ln. Betel-nut Palm E *Dictyosperna album (Bory) H. A. Wendl. & Drude ex Scheff. Princess Palm E *Cocos nucifera L. Coconut Palm E * Syagrus romanzffiana (Chamisso)Glassman Queen Palm E *Aiphanes caryotifolia (Kunth) H. A. Wendl. Coyure Palm E Bactris gasipaes Kunth Peach Palm E

* Either adults, larvae or damage of R. obscurus seen by K.H.H. Palm classificationafter Uhl and Dransfield (1987). abdominale (Fabricius) (Hydrophilidae) and at the base of inflorescences. Adults andPlatysoma sp. (Histeridae)were found were not observed causing damage in the in weevil infested Metroxylon at Cape palms, although R. Goebel (pers. comm.) Tribulation, but it is not known if these reported numbers damaging the flowers of were actually preying on R. obscuruslar- coconut. Adult feeding scars are recorded on sugar cane. It is not known where the eggs are laid although it is suspected that Damage(Figs 3-6) they are mostly deposited in the leaf bases. Larval damage has been observed from Adult fi. obscurus were found shelter- just above and adjacent to the root mass ing under leaf basese.g., on Wodyetia, to two meters or more above the eround. 206 PRINCIPES lVoL. 35

In younger palms the larvae mine the cen- pest Sitophilus, and the bananapests Cos- tral portion of the stem, completely nl,opolites and Polytus. Severalother gen- destroying the plant. Damage extends up era are important palm pestsincluding the and down the stem for a number of cen- large Rhynchophorus spp. (up to 55 mm timeters from the initial point of entry. In in length) and the smaller Diocalandra older palms Iarvae mine the thicker leaf spp. (6-8 mm). Although the asiatic palm bases,e.g., Metroxylon and Pigafetta, as w eevil Rhyncho pho rus fer rugineus (Ohv- well as extending for a short distance into ier) has not yet been found in Australia, the trunk. Splitting occurred in specimens the four-spotted coconut weevil, Dioca- of Wodyetiawith a trunk diameterof about landr a frumenrl (Fabricius)is occasionally 100 millimeters. taken in coconutsin northern Queensland The obvious external symptoms of lar- where it seems to be secondary to R. val feeding in palms are listed below. The obscurus.Hill (I983) statedthat the pest "'windowing" which occurs in sugar cane status of D. frumenti was open to dispute. was not observed. It appears, from comments made by growers interviewed and by the numbers jellyJike in leaf (i) A exudate from holes of enquiries received, that the incidence (Fig. 3) basesandlor stems of R. obscurus in palms in northern or near the (ii) Splitting of the trunk at is increasing. There would seem (Figs. Queensland base and further up the trunk to be two factors contributing to this-the 4.5) dramatic increase in number and size of (iii) especiallyif the Staining of the trunk, plantings of palms for the nursery trade, of lar- palm sustainsa high population and the trend back to green cane harvest (Fig. vae 6) in the sugar cane industry. Although there of In young palms and older individuals is no direct evidence, we believe that R. decaryi and somespecies, e.g., Neodypsis obscurus infestationsin newly established sis,the Chry salido car pus madag ascarien nurseries primarily come from infested internal mining by larvae can causedeath plants received from older established at of the plant. Quite often a large area nurseries. Indeed this is backed up by the base of some specieswill be destroyed recent outbreaks in southern areas (Ham- leaving the palm susceptible to lodging. ilton Island and Southport in Queensland cause Holes and splitting of the trunk dis- and even into New South Wales) where figurement in older plants making them R. obscurushas not previouslybeen known unsuitable for sale. to occur. Once establishedin a nursery, spirally Pupation occurs in a case of populations build up giving the impression wovenfibers. In somespecies, e.g., Chry- that the problem is increasing. The long salidocarpus lutescensand Carpentaria term effect of the sugar cane industry acunxinata, large numbers of pupal cases returning to green harvest is not known. were observedprotruding through splits in Although unburnt fieldsfavor weevil devel- the trunk. These splits were presumed to opment, modern cane varieties are much Pupal be causedby extensivelarval feeding. harder than those used earlier in the cen- caseswere also found at ground level within tury and are much less susceptibleto R. the remains of the trunks of dead plants. obscurus attack (K. Chandler, pers. comm.r. Discussion To control the weevil, most growers R. obscurus is a member of the weevil undertake routine crop hygiene, e.9., subfamily Rhynchophorinae which includes removal and destructionofdead fronds and many genera of economic importance, infected material. Chemical control mea- including the well known stored products sures are not yet approved by the Depart- l9erl HALFPAPPAND STOREY:CANE WEEVIL BORER 207 ment of Primary Industries in Queensland Hrr-1, D. S. 1983. Agricultural insects pests of the but would undoubtedly have a place in a tropics and their control. 2nd ed. Cambridge University Press. 746 pp. (1968) well managednursery. Zimmerman JARvIS,E. 1927. Notes on insects damaging sugar believed that satisfactory biocontrol of R. cane in Queensland.Qld. Bur. Sugar Exper. Sta. obscurus would be exceedingly difficult. Division of Entomology. Bull. 3: 13 15. The tachinid L. sphenophori has been LEVER,R. J. A. W. 1969. Pests of the coconut Agricultural StudiesNo. 77: l-19O. establishedin the area for 79 years and palm. FAO MuNcounRv, R. W. 1937. Progressreport of Sugar is unlikely to becomemore important than Cane Beetle Borer Investigations in North at present. Previous attempts (at least 5 Queensland.Proc. Qld. Soc. Sugar Cane Tech- between l92I-28) to introduce the his- nologists 8th Annual Confer. Cairns Qld: 49- terid P. jauanus have failed and it is 62. MUNcoMERY, R. W. 1953. The rise and fall of unlikely that regulations now in force would the Sugarcaneweevil borer Pest in Queensland. allow importation into Australia of such a Proc. Int. Society Sugar Cane Technologists8th general predator as a biocontrol agent. CongressJamaica: 586-593. Further work on the problem should MuIn, F. arl O. H. Swrznv. 1916. The cane involve studieson the biology of R. obscu- borer beetle in Hawaii and its control by natural enemies. Hawaiian Sugar Planters Assoc. Exp. nrs in palm hosts,including egg laying sites Sta. (Ento. Ser). Bull. 13: I-102. and host susceptibility(Zimmerman 1968) Nepouprrn, 8., T. Nrssroe, eNl W. C. Mrrcnrrr. felt that sick or injured palms were more 1972. Biology and rearing methods ofthe New prone to weevil attack). Trials of chemical Guinea Sugarcaneweevil, Rhabdoscelus obscu- rzs. Hawaii Agric. Exper. Sta. College of Trop- control measures, their usefulness, best ical Agric. U. of Hawaii Tech. Bull. 85: l-51. formulationsand applicationtechniques and Usr, N. W. eno J. Dnensrlnro. 1987. Genera timing would also be of benefit to the palm palmarum. A classification of palms based on nursery industry. the work of Harold E. Moore, Jr. Allen Press, Lawrence,Kansas. 6I0 pp. VeN Zwaruwsr,rsrnc. R. H. ANDJ. S. Rosa. I940. Acknowledgments Field movement of Sugar Cane Beetle borer adults. Hawaiian Planters Record. 44: 3-6, Thanks go to Maria Walford-Huggins, WernnHousr, D. F. eNo K. R. Nonnrs. 1987. Keith Chandler and Roger Goebel for Biological Control: Pacific Prospects. Inkata advice on palms, weevils and the sugar Press, Melbourne. 454 pp. industry. Karen Koch provided the pho- WILSoN, F. 1960. A review of the biologicalcontrol tograph for Figure l. Neil Goughand Brian of insects and weedsin Australia and Australian New Guinea. CommonwealthInstitute of Biolog- Cantrell read and commented on the ical Control, Technical communication No. I: manuscript. This paper would not have 7-to2. been possible without the cooperation of Wrooen, J. A. 1932. The BananaWeevil Borer. the many palm growers interviewed. Brief notes on Plaesiusjavanus Er,, The Histerid Predator.Queensland Agri. Jour. 38;24-29. Zturrtrnuan, E. C. 1968. Rhynchophorinae of LttnRetuRn CIrnn South eastern Polynesia. Pacific Insects l0 (l): 47-77. DHARMARAJU,E., A. BERGER,M. Urupaco, aNn E. AUPAAII. 1979. The sugar cane weevil on Coconuts. Alafua Aeric. Bull. 4: 8-9.