Models of Traps for the Coconut Pests Rhyncophorus Bilineatus and Scapanes Australis and Their Trapping Efficiency in Papua New Guinea

MODELS OF TRAPS FOR THE COCONUT PESTS RHYNCOPHORUS BILINEATUS AND SCAPANES AUSTRALIS AND THEIR TRAPPING EFFICIENCY IN PAPUA NEW GUINEA

Titus Kakul 1/ , Dr. S. Laup2/, Mr. R. N. B. Prior 2/. Dr. Didier Rochat 4/, Dr. Jean Paul Morin,(3) ,P. Gende, S. Embupa(2) & Dr. L. Ollivier (3)

Abstract

The beetle pests Scapanes australis, Oryctes rhinocerous and Rhyncophorus bilineatus have been major constraints to coconut production in the Islands region of Papua New Guinea for the last 30 years. Efficient synthetic attractants able to lure and trap all three beetles have been developed. This paper describes several trap designs developed at the Cocoa and Coconut Research Institute and the results obtained for their trapping efficiency in the laboratory and the field. A modification of the “Titus Bucket” trap increased the number of R. bilineatus caught threefold and of female Scapanes twofold. PVC pipe traps caught more Scapanes than the modified “Titus Bucket” trap.

The importance of well design traps and their use for specific purposes are discussed.

Key words: Coconuts, Scapanes australis, Oryctes rhinoceros, R. bilineatus, traps, synergist.

______1/ Cocoa & Coconut Research Instutute (CCRI), P. O. Box 642, Madang, Papua New Guine.a Email: [email protected]; 2/ Cocoa & Coconut Research Institute (CCRI), P. O. Box 1846, Rabaul, Papua New Guinea; 3/ Centre International de Recherche Agronomique pour le Developpement (CIRAD-CP), TA 80/PS3, Bd de la Lironde 34398 , Montpellier Cedex 5, France; Email: : [email protected]; 4/ Institut National de la Recherche Agronomique (INRA) UR 258, 78026, Versailles Cedex, France. Email:

1 1. INTRODUCTION The attractant mixture used in all field trials consisted of the insect pheromone with host plant The Islands region is a major copra material as the co-attractant. The beetle producing area in Papua New Guinea (PNG). A pheromones were: number of beetle pests are a constraint to S. australis : 90:5 v/v of 2-butanol and acetone production. The boring into coconut crowns by (Rochat, et al, 2000); Scapanes australis Boisd (Col.,Scarab.) and R. bilineatus: 4-methyl-5-nonamal (Oehlschlager, Oryctes rhinoceros Linn (Col.,Scarab.) is usually et al., 1995); followed by damage from Rhynchophorus O. rhinoceros: Ethyl 4-methyloctanate (4-MOE) bilineatus Mont. (Col., Curcul.). They mainly (Hallet, et al., 1995, Morin, et al., 1996). attack and kill young coconut palms (Prior. et al., 2000) preventing new planting for rehabilitation of The host plant co-attractant was two pieces old coconut plantations. The damage from R. of split sugarcane stalk or two pieces of split bilineatus is often severe and palms may even die. coconut seedling crown.

Field experiments for trapping R. bilineatus Laboratory assay began in the PNG Cocoa and Coconut Research Institute, Rabaul (CCRI) in 1991 (Anon., 1991). The efficacy of four different trap designs However, after six years of trapping and many was first evaluated in the laboratory for their thousands of R. bilineatus lured into traps, there beetle retention. Three retention agents were was no reduction in pest damage levels (Anon., treatments for: 1) Control (no retention agent); 2) 1993). It was later observed that the traps used water only; and, 3) soapy water. The treatment were not efficient, catching only 10% of the combination was factorial giving twelve beetles that flew towards them (Anon, 1998). treatments. Each treatment was replicated three Therefore, this study was initiated to determine times and 10 BPW were placed in each trap. The trap designs and various attractants to increase number of weevils remaining in the traps was trapping efficiency in the field. counted daily for seven days.

The efficiency of TBT and the PDT, 2. MATERIALS AND METHODS designed to trap dynastids, were compared in the laboratory for the retention of Scapanes. The Four Designs Rhynchophorus trap (Figure 1) retention agents were water and soapy water were tested. Trap one was the Laup bamboo trap placed in the traps. The treatment combination (LBT) which consisted of one inter-node of giant was factorial giving four treatments. There were bamboo, with two entry holes (5 cm width and 10 ten replicates (ten traps) of each treatment and six cm height) on opposite sides, 20 cm from the (3 male and 3 female) adults of Scapanes placed bottom internode. The second trap was the inside each trap. The traps were hung in the Oehlschlager Palm Weevil Trap (OPWT) which is laboratory, and the Scapanes present in the trap made up of a 10-litre bucket with entry slots (2 cm were counted daily. in width, 5 cm length) in the sides and a lid (Oehlschlager. et al., 1993). Trap three, the Prior Field testing of traps Dynastid Trap (PDT), is made up of a 10-litre bucket with (two entry windows 13 x 7.5 cm cut in Field Trial sites the sides 15 cm above the base and two small slits about 5 cm up from the base, to allow excess water Trials 1 and 2 were carried out to drain out. Trap four is the Titus Compound consecutively under cocoa and young coconut Bucket Trap (TCBT) (Kakul. et al., 1999) that stands at block 12, Tavilo plantation, East New included a food container (height 19 cm, top Britain Province, Papua New Guinea in 1998. The diameter 21 cm and base diameter 16 cm) with traps were cleared on a weekly basis. Trial 3 was many small holes approximately 0.5 cm apart in it carried out at Kervera plantation, not far from for air circulation inside the PDT. Tavilo, in 2000. The plantation consists of inter- cropped cocoa and coconut. The field testing of Attractants Scapanes trap was carried out in a block of cocoa

2 and young coconut at Tokiala, plantation 600 3. RESULTS metres to the north of Tavilo. 3.1 Laboratory Test The traps were placed 50 metres apart. Bucket traps were either hung on a cocoa branch The results from laboratory assays showed or coconut leaf petiole 1.5 metres above the the use a of soapy water as a killing agent gave ground. The PVC traps were placed on the ground, absolute mortality in the Oeshlschlager and Titus supported with wooden pegs. traps (Figure 4). Retention was high (50%) in LBT traps compared to the other designs tested. With Field Trials the addition of pure water, the TBT and OWT traps retained more than 50% of the test insects. In Trial 1 the traps were modified by The best results were observed with the use of wrapping fibrous coconut leaf sheath (being soapy water which resulted in 100% mortality in referred to as bilas [BL]) (Figure 2) in a replicated the TBT and OWT, but only 83% in LBT traps. trial. The four treatments were as follows; 1. TBT, The detergent in soapy water lowers surface 2. LBT, 3. BL TBT, 4. BL LBT. The trial design tension and promotes wetting of beetles, resulting was a complete randomised block with 12 in drowning. replications. The laboratory test results for Scapanes In Trial 2 the relative efficiency of shelves indicated that TBT gave absolute retention even (S) attached to palm weevil traps as a landing without a killing agent (Figure 5). The TBT surface for the weevils was examined in a appeared to retain all the test insects, whereas the replicated experiment. The four treatments were as PDT was poor without a killing medium. Insect follows; 1) BL, OWT; 2) BL, OWT and S; 3) BL, mortality was high in both traps when soapy water OWT, S; and four live R. bilineatus weevils in was used, but was low without a killing agent. each trap (2 males and 2 females); and, 4) TBT. The trial design was a complete randomised block 3.2 Field Assays with 12 replications. The effect of modifying the traps by Field trial 3 examined the relative efficiency wrapping fibrous coconut pads to provide landing of the BL TBT in trapping the three beetle pests of surfaces and a visual cue for R. bilineatus adults coconut in Kervera plantation (100 metres south of was clearly demonstrated with highly significant Tavilo) in 1998. The TBT was designed to (P<0.01) increase in the number of weevils caught capture both the black palm weevil and the two in the modified traps than the standard traps. The dynastids and was thus chosen for further testing modified TBT (TBT BL) was catching in the field. The two treatments were: 1) BL TBT; significantly (p<0.01) more R. bilineatus adults and, 2) TBT. There were 25 replications (traps) than the other traps (Figure 6). The other traps, and the trial design was completely randomised. especially LBT trap, was shown to be poor in catching these weevils. No differences in catch Field trial 4 examined the efficacy of the were observed between the TBT and LBT BL. new Scapanes trap designs. A PVC tube was used In Trial 2 the effect of platform on trap to construct this trap (Figure 3) and the TBT was entrance as a landing surface was not significant used as a standard trap. The treatments were 1) (Figure 7). The effect of resident weevils on Titus Bucket Trap (TBT); 2) PVC Pipe Large retaining weevils captured was significant (PVCPL) 15 cm diameter X 200 cm length. 3) (P< 0.01). PVC Pipe Medium (PVCPM) 10-cm diameter X 200 cm length. There were twelve replications and The efficacy of TBT (Trial no. 3) in trapping the trial was a completely randomised design. The all three beetles showed that modified traps caught traps were placed 50 metres apart. significantly (P<0.01) more R. bilineatus than the standard trap (Figure 8). The modified trap also All the beetle count data were transformed caught significantly more female Scapanes and O. using the square root transformation and then rhinoceros than the standard traps. The number of subjected to ANOVA using the Microsoft Excel Scapanes caught in both trap types did not differ Data Analysis Function. significantly.

In trial 4 the trap effect was highly The use of shelves or pads as landing significant (P = 0.01), with the two PVC Trap surfaces for the weevil resulted in a reduction in designs catching more beetles than the TBT the number of weevils caught. The platform may (Figure 9). Pieces of sugar cane were hung inside provide an opportunity for the beetles to alight and the PVC Traps as kairomones and this helped then fly off again. The resident weevil in traps improve insect catches. (treatment 3) did not enhance captures relative to the bilas trap (treatment 1), but their effect in retaining the weevils in the trap relative to bilas 4. DISCUSSION and shelves (treatment 2) was significant (p= 0.5). This implied that shelves are not a necessary part Preliminary screening of the various of the trap. Rhynchophorus traps in retaining weevils clearly demonstrated the importance of a well-designed Sole trapping of individual species is costly trap, which would minimise the number of beetles and inappropriate in the case of the coconut escaping. A low number of beetles present in the beetles as they share the same habitat and attack plantation can still cause economic damage to the same plant. A highly positive correlation of coconuts. The results obtained further suggested attack between the weevil and the two dynasties the importance of using appropriate trap and has been shown (Kakul, et al, in preparation). killing agents for specific uses. For instance, TBT However as the synergist plant material was not and OWT can be used in situations where the the same for Oryctes rhinoceros (Alfiler, 1999, objective of trapping is lure and kill. When the Sudharto. et al. 2001), this pest should be trapped objective of trapping is to release with a different trap combining 4-MOE and empty entomopathogens via traps then PDT and LBT are oil palm fruit bunch (EFB) (Morin. et al. 2001). If more appropriate as the insect can go into the trap, EFB is not available, rotting palm trunk can be get itself contaminated and then escape. The PDT used (Alfiler, 1999). For R. bilineatus and S. had been used successfully to spread the australis, the TBT was selected to be further tested Baculovirus among Oryctes rhinoceros in East in the field because the two insects use the same New Britain province in the past (Prior. Et. plant material synergist (fresh coconut bulb or Al.1995). pieces of sugarcane).

TBT gave complete retention for Scapanes even BL TBT caught more female Scapanes than without a retention agent. It is appropriate for the non BL TBT. The difference is huge in terms trapping Scapanes in tropical conditions where the of the ability of Scapanes to sustain its population liquid retention agents tend to dry up rapidly. Liquid retention agents are not necessary when the and continue to cause economic damage to the traps are intended to catch Scapanes. coconut cultivation. A coconut can die if it is attacked by a Scapanes and the wound is than Bilas Traps mimic the natural host of the infested by R. bilineatus. The Scapanes attack beetles where resident weevils in wounds of host coconuts for up to seven years and a female are inconspicuous and the emigrant insect would Scapanes lays an average of 52 eggs. have to crawl into the palms guided by chemical cues. The non-bilas trap used in the past did not The PVC trap can now be used to trap the lack attraction but failed to capture the weevils. three beetles. A synthetic synergist for the O. This was because the weevils require a landing rhinoceros beetle is not yet available and rotting surface to alight on and then crawl into the traps. It coconut wood parts can be used as a pheromone is possible that the pheromone could have drawn synergist and in the PVC trap. The PVC trap may in many more weevils from outside the immediate look like an old coconut trunk in the dark. The trapping area. This may explain why mass three beetles cannot escape once caught in the dark trapping of R. bilineatus in the past was not because of the limited space available for them to effective in reducing losses of coconuts (Anon, manoeuvre (rotting coconut trunk parts at the 1998). Bilas not only enhanced the efficacy of the bottom of the traps). The trap can remain in the traps but also increased the durability of the bucket field for at least two months as long as the traps by protecting them from direct solar radiation.

4 attractants do not run out. Killing agents such as Kakul, T. K., Laup, S., Stathers, T., Beaudoin- water or insecticides are not necessary in this trap. Ollivier, L., Morin, J. P., and Rochat, D. (1999). Trapping and disruption of the The cost of PVCL was (US $12), three times mating activity of Scapanes australis the cost of TBT (US $4) and twice the cost of using live male as bait in Papua New PVCM (US $6). However, the PVC pipes traps are Guinea. CORD 15 (2), 131 –145. more durable than the bucket traps. The correct dimensions of PVCM traps were not followed Kakul, T.K., Laup, S., Prior, R.N.B. Rochat, D., when making the traps. Manufacturing the PVCM Morin, J.P., Embupa, S., Gende, P., and, trap using the right measurements will increase the Ollivier, L.; The Impact of Olfactory beetle catches to the same level as PVCL, thus Trapping Scapanes australis: A major pest further reducing the cost of PVC traps. of coconut in Papua New Guinea (In preparation)

ACKNOWLEDGEMENTS Morin, J.P, Sudharto, P.S., Purba, R, Desmier de Chenon, T. Kakul, S Laup, L. Beaudoin- R. Minana and entomology section labourers Ollivier and, Rochat, D.; 2001. A new for persistent commitment to field trapping and type of trap for capturing Oryctes assessment. Coconut Products Limited and rhinoceros (Scarabaeidae, Dynastinae), the main pest in young oil palm and NewMark Plantation Management Ltd. for coconut plantings. CORD, 17(2): 13-21. allowing us to use Gunanur and Tokiala plantations, thus providing the necessary coconut Morin, J.P., Rochat, D., Malosse, C., Lettere, M., field experimental sites. This paper is published Desmier de Chenon, R., Wibowo H., and, with the permission of the Directors of PNG Descoins, C. (1996). Ethyl 4- CCRI. We are also indebted to the European methyloctanoate, major component of Union for funding under INCO project Number Oryctes rhinoceros (L.) (Coleoptera, RB-IC 18CT970199 and Dr. Y. Efron, Dr. L. Dynastidae) pheromone. C.R. Acad. Sci. Kuniata, Mr. M. Powell for comments on the Paris, Sciences de la vie. 319: 595-602. manuscript. Sudharto, P.S., Purba, R.Y., Rochat, D., and, References cited Morin J.P. (2001). Synergy between empty oil palm fruit bunch and synthetic Alfiler, A. R. R. (1999). Increased attraction of aggregation pheromone (Ethyl 4- Oryctes aggregation pheromone, Ethyl 4 – methyloctanoate) for mass trapping of methyloctanoate, with coconut wood, Oryctes rhinoceros beetles in the oil palm CORD 15(2): 106-114. plantation in Indonesia. PORIM International Palm Oil Congress, Kuala Lumpur, Malaysia, Aug. 20-23. Anon. 1991. Annual Report of the Papua New Guinea Cocoa and Coconut Research Institute. Oehlschlager, A.C., Prior, R.N.B., Perez, A.L., Gries, R., Gries, G., Pierce, H.D. Jr., and, Laup, S. (1995). Structure, chirality, and Anon. 1998. Annual Report of the Papua New field testing of a male-produced Guinea Cocoa and Coconut Research aggregation pheromone of Asian palm Institute. weevil Rhynchophorus bilineatus (Montr) (Coleoptera: Curculionidae). J. Chem. Hallet, R.H., Perez, A.L., Gries, G., Gries, R., Eco. 21: 1619-1629. Pierce, H.D. Jr., Yue, J., Oehlschlager, A. C., Gonzalez, L.M., Borden, J.H., (1995). Rochat, D., Ramirez-Lucas, P. Malosse, C., Aggregation pheromone of the coconut Aldana, R., Kakul, T., and, Morin, J. rhinoceros beetles Oryctes rhinoceros (L) (2000). Role of solid phase micro- (Coleoptera: Scarab). J. Chem. Ecol. 21: extraction in the identification of highly 1549-1570. volatile pheromone of two Rhinoceros

5 Beetles Scapanes australis and Strategus aloeus (Col., Scarabaeidae, Dynastinae). J. Chrom. A. 885: 433-444.

Prior, R. N. B., Morin, J. P., Rochat, D., Beaudoin- Ollivier, L., Stathers, T., Kakul, T., Embupa, S., Naguai, R. (2000). New aspects of the Biology of the Melanesian Rhinoceros beetle Scapanes australis (Col: Dynastidae) and Evidence for field attraction to males. J. Appl. Entomol. 124: 41-50.