E NTOMOLOGY V. Soroker et al. (2005) Phytoparasitica 33(1):97-106 Current Status of Red Palm Weevil Infestation in Date Palm Plantations in Israel V. Soroker,1,∗ D. Blumberg,1 A. Haberman,2 M. Hamburger-Rishard,2 S. Reneh,1 S. Talebaev,1 L. Anshelevich1 and A.R. Harari1 The red palm weevil Rhynchophorus ferrugineus (Olivier) (RPW) is the most serious pest of date palms in the Middle East. Weevil infestation was first detected in Israel in the summer of 1999 in date plantations in the Jordan Valley, on the west bank of the Jordan River and in the northern area of the Dead Sea. For 2 years following the discovery of the pest, prophylactic insecticide chemical treatments as well as adult weevil trapping were carried out over 450 ha of date palm plantations. Traps loaded with a commercial aggregation pheromone, ferrugineol, supplemented with ethyl acetate and a fermenting mixture of dates and sugarcane molasses, were posted in high trap density (approx. ten traps per ha) in order to monitor weevil infestation and reduce the RPW population by mass trapping. A significant decrease in number of trapped beetles and infested trees was observed in 2001 and continued in the following years. No infested trees have been found since 2002, indicating a decrease in RPW population. The sex ratio of trapped adults during 3 years of study was significantly female-biased (∼2.5:1). Therefore, mass trapping might have played a significant role in the suppression of RPW populations in date plantations. KEY WORDS: Red palm weevil; Rhynchophorus ferrugineus; adult mass trapping; sex ratio; date palm; aggregation pheromone. INTRODUCTION The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is a serious pest of various palm species including dates (6). The immature stages develop within the tree trunk, destroy its vascular system and eventually cause the collapse and death of the tree. The pest is widely distributed, occurring in Oceania, Asia, Africa, Europe (Spain) and the Middle East (6). It causes severe damage to coconuts in South East Asia and to date palms in the Middle East. The weevil appeared in the Middle East in the 1980s and has caused severe damage to date production by destroying thousands of trees (13). In Israel and Jordan, infestation was first reported in 1999. It is commonly accepted that the weevils are attracted to dying and damaged parts of palm. This, however, does not preclude attacks to undamaged palms as well. The weevils may fly relatively long distances, ∼ 1 km per day, in the daytime, and are active for most of the year (15). Mating in RPW is mediated by an aggregation pheromone produced by the male weevil. The aggregation pheromone is composed of two components: ferrugineol (4-methyl-5nonanol) – the major component, and 4-methyl-5-nonanone – the minor one (8,19). The Received Oct. 7, 2003; accepted Nov. 15, 2004; http://www.phytoparasitica.org posting Dec. 19, 2004. 1 Dept. of Entomology, ARO, The Volcani Center, Bet Dagan 50250, Israel. *Corresponding author [Fax: +9723-9683831; e-mail: sorokerv@agri.gov.il]. 2 Plant Protection & Inspection Services, Israel Ministry of Agriculture, Bet Dagan 50250, Israel. Phytoparasitica 33:1, 2005 97 activity of 4-methyl-5-nonanone was demonstrated for the first time by workers in Saudi Arabia and reported in the FAO by Oehlschlager (15). The adults were reported to be highly attracted by the combination of aggregation pheromone and the volatiles secreted by palm trees (7,8,10,22). The main methods employed to control adult weevils in date and coconut plantations worldwide consist of monitoring and mass trapping, using bucket traps loaded with the pheromone blend and food bait (9,12,16,17,26). This pheromone–food bait is often supplemented with pesticides to prevent weevils from escaping from the trap. In Israel intensive IPM measures were initiated in August 1999, following the first reports of weevils present in date palm plantations. The control measures taken included the use of pheromone traps for mass trapping and monitoring of adult weevils, repeated insecticide treatment as prophylactic applications, timely curative treatment of the infested palms, destruction of heavily damaged palm trees and, most important of all, applying strict quarantine regulations to prevent the trade and transport of palms and offshoots outside the infested area. This paper summarizes the results in Israel of using a mass trapping technique for monitoring and control of RPW, in addition to the other methods mentioned above, during the years 1999–2003. MATERIALS AND METHODS Survey Since the discovery of RPW in the Jordan Valley and northern Dead Sea area of Israel, all date plantations in the region have been inspected regularly, every 7–10 days, for trapped beetles and newly infected trees. Trees in areas of frequent trapping were inspected for characteristic symptoms of RPW infestation, such as oozing from the tree trunk or crown drying. Acoustic monitoring (23) as well as dogs trained to detect oozing were also employed (14). Monitoring Routine monitoring took place from August 1999 to September 2002, in the northern part of the Jordan Valley and along the Arava Valley. Traps were placed at a density of one trap per 3 ha. The total area of routine monitoring was ∼2200 ha. Mass trapping From August 1999 to September 2001, mass trapping was operated, as a control method, by placing 5000 traps at a density of ten traps per ha, over 450 ha of date palm plantations, parks and gardens along the Jordan River and north of the Dead Sea (about 70,000 trees). In addition, a detailed mass trap monitoring of weevils was conducted in the date plantations of Kibbutz Almog (32 ha) in the area north of the Dead Sea. In this area 420 traps were distributed, at a density of approximately one trap per 900 m 2 . In order to follow weevil spatial distribution, we arbitrarily divided the trapping area into distinct zones. A zone was defined as a group of plantations separated from other date-growing areas by more than 1 km. All traps were set next to the tree trunks at ground level. The traps consisted of a 10-l upright bucket baited with the male aggregation pheromone, ferrolure (ChemTica International, San José, Costa Rica), supplemented with ethyl acetate plus a fermenting mixture of dates and sugarcane molasses, as described by Zada et al. (29). The traps were inspected regularly once a week from April to November (at ambient high temperature) and once in 2 weeks during the months of low temperatures, from December to March. Water was added to the traps regularly to maintain the fermentation process. The fermenting 98 V. Soroker et al. Fig. 1. A map of the red palm weevil-infested area. Black dots indicate areas of tree infestations and intensive trapping. White dots indicate areas where trappings were recorded. 1, Tirat Zevi; 2, Bizat Argaman; 3, Zor 58; 4, Massua; 5, Fazael; 6, Zor 83; 7, Yitav; 8, Na’ama; 9, northern Dead Sea coast; 10, Elat. mixture was renewed once in 2 months. The pheromone was replaced every 2–3 months during summer and once during winter when it became exhausted. All together, four or five lure packs were used per year per trap. The trapped weevils were sexed according to gender-specific external characteristics of the rostrum according to Booth et al. (2). In males, the rostrum is almost four-fifths the length of the pronotum, covered on the apical part with dense erect setae, whereas in females no such setae are visible. To evaluate whether trapping removes young females with high egg-laying potential, trapped live females were taken to the laboratory, where they were provided with food and oviposition substrate, as described below. Egg laying and hatching larvae were recorded. In an attempt to monitor weevils when leaving the infested tree, three infested trees were caged individually in a mesh tent (1 mm mesh size) and one pheromone trap was set inside the cage, next to each tree. In September 2001, due to a decrease in weevil catches, only 20% of the traps (∼1,200 traps) were kept for mass trapping. Trap density was reduced to one trap per 0.7 ha in infested plantations and one trap per 3 ha in areas where no beetles had been previously caught. Phytoparasitica 33:1, 2005 99 Chemical control Pesticides were used in the infested areas both as preventive and curative treatments. Prophylactic methods which were taken from May 2000 to August 2001 to prevent weevil attack on offshoots, included trunk sprays (up to 2 m high) from May until July twice a month with azinphos-methyl 0.2% or with diazinon 0.3% along the northern coast of the Dead Sea, and chlorpyriphos 0.15% in the Jordan Valley (total of ∼1133 ha). Curative methods for RPW-infested trees included stem infusion with dichlorvos 100 (10%), or soil application of imidacloprid (Confidor, Bayer) at 5–10 cc per tree, three times at monthly intervals. In the case of an infested plantation, all the young, offshoot-bearing trees were treated. In August 2002, all trunk sprays were stopped. Phytosanitation Heavily infested trees (four trees) were uprooted and burned. The trunks of moderately infested trees were treated with the above mentioned curative treatments. Subsequently, trees were wrapped in dense plastic net (mesh 17–20), to prevent possible escape of adult weevils. Quarantine Quarantine regulations were enforced against transportation of offshoots out of the infested areas (total of ∼1133 ha). Laboratory culture Culture of RPW was established in the laboratory on freshly shredded sugarcane tissue that served both as food and oviposition medium according to Rahalkar et al. (20). RPW were kept individually, at 27–29◦ C, from the second larval stage to adult emergence. Upon emergence, adults were sexed according to the characteristics described above in order to determine the sex ratio of the adult population. RESULTS Since the initiation of mass trapping and monitoring of weevils in August 1999, a total of approximately 600 weevils had been trapped and about 60 trees were reported as infested. No new infested trees have been detected since 2002. Most of the trapping took place in several distinct zones in the Jordan Valley (Fig. 1). Infested trees were detected in three areas only: the northern coast of the Dead Sea, Zor 83 and Bizat Argaman. The highest number of trapped weevils was recorded during the summer of the first year of the study (1999) and in the following year (2000) (Fig. 2). Subsequently, the number of trapped weevils declined, with only a few individuals trapped during the summer of 2002 and even fewer in 2003. In these years two peaks of catches were observed, one during April–June and the other during August–October. The distribution of the trapped weevils changed during these years. Whereas in 1999–2000 weevils were trapped in 14 date plantations located in eight distinct zones (Fig. 3), in 2002 weevils were trapped only in eight plantations in four zones, and in 2003 only a few individuals were trapped – and those mainly in two zones. In the Jordan Valley, seven geographically separated infestation zones were defined. The minimum distance was between Bizat Argaman and Zor 58 (3.1 km) and the maximum was ∼30 km between Zor 58 and Tirat Zevi. The distance between the major trapping areas, the northern coast of the Dead Sea and Zor 83, is approximately 30 km. Local distribution pattern of weevils in the date plantation of Almog showed that during the high infestation periods, which occurred during 2000–2001, weevil distribution was clumped (CD=2.7 and 2.3, respectively) and weevils were caught in only ∼20% of traps. In fact, the highest number of adults were trapped in a few adjacent traps, whereas most other traps caught no weevils. In two cases, high trapping in a specific area led to detection of two 100 V. Soroker et al. infested trees which were successfully treated by pesticides as described in the Materials and Methods section. Monitoring weevils in traps in- and outside the three caged infested trees revealed more trapping in the trap within the cage rather than in the adjacent trap located outside of the cage. In 2002 the population decreased significantly and the pattern of the weevil population in Almog plantations approached random distribution (CD=0.98). TABLE 1. Cumulative numbers of red palm weevil from the trapped population and from laboratory culture Population Year In traps 2000 2001 2002 2003 In culture 2000–2003 ∗ Probability that sex ratio is 1:1. ∗∗ Binomial distribution. Females Males Total Ratio (F/M) 193 65 20 7 101 86 17 6 3 69 279 82 26 10 170 2.2 3.8 3.3 2.3 1.5 Probability∗ (x2 ) P<0.001 P<0.001 P<0.01 ∗∗ P=0.17 P<0.05 Fig. 2. Total number of adult red palm weevils captured per month between 1999 and 2003. ∗ Trapping in 1999 started in August. The sex ratio of trapped adults was consistently and significantly female-biased (72% of total catches were females), with 2.2 to 3.8 times more females than males captured in traps (Table 1). In comparison, the sex ratio of weevils in the lab culture was only 59% in favor of females. Phytoparasitica 33:1, 2005 101 Fig. 3. Annual distribution of red palm weevil trappings by location. DISCUSSION The date palm is one of the most economically important crops in Israel. It is a very intensive crop for both local consumption and for export, producing an income as high as approximately $3500 ha−1 . Therefore, the danger of RPW spread is of great importance, and increasing production costs by implementation of IPM along with quarantine measures has proved economically sustainable. Data collected in the last 4 years indicate that spread of the weevil population has been confined to the quarantine area (Fig. 1), and its size has been reduced significantly. Special emphasis was given to environmentally friendly control methods using pheromones. Pheromones have been implemented extensively in monitoring and control management of various pests and habitats (23). The use of pheromones for trapping of RPW seems to be an efficient means of monitoring the pest in date plantations in Israel. There are apparently two peaks of adult catches during the year, one in April–June and the other in August–October. The first peak is likely to represent the emergence of the first generation and agrees with findings in the Kingdom of Saudi Arabia (KSA), United Arab Emirates (UAE) and Egypt, which show highest capture rates in the spring, after the cold months (15). The following peak is likely to correspond to the emergence pattern of the second generation. The trapped adults and the location of the infested trees indicate a pattern of patchy distribution of RPW population at both the plantation and regional level. The aggregated distribution of RPW population was also detected in coconut plantations of Goa by Faleiro et al. (4). The aggregation pattern found in this species may be the result of (a) limited breeding sites, whereas females and males are attracted to specific trees, e.g. already 102 V. Soroker et al. damaged trees; and (b) females ovipositing a batch of eggs in one tree. In the present study, at the area level, two major spots of trappings were still maintained in 2003, in addition to a few weevils trapped elsewhere. We believe that the major trapping areas are correlated with the location of the infested trees. Since the two major trapping areas are separated by more than 30 km, a distance much greater (about 30 times) than the normal flight range of the weevil in a day (15), we suspect that the weevil has established at least two independent populations and that human activity, such as transport of the infested offshoots between plantations, is likely to have contributed to this pattern of pest distribution. However, it is also possible that during their lifetime the long-lived weevils could travel much larger distances. The flight pattern of the weevils in the date plantation is still unknown. Most of the trapped adults were concentrated in a few traps and in some cases an infested tree was later found in close vicinity to the active traps. These trapped weevils could have been caught on their way to the infected tree or away from it. The distance at which they perceive and react to their pheromone and to plant volatiles has not been determined and, whether they are attracted or rejected by trees infested with conspecifics is yet to be studied. By using trees covered with a screen tent, we demonstrated that adults emerging from the infested tree are trapped in pheromone traps positioned nearby, but this does not exclude the possibility that weevils are attracted to the infested trees from remote areas. Indeed, a long-distance attraction to pheromone traps was demonstrated for R. palmarum. Since mass trapping of R. palmarum in oil palms is conducted with traps at a density of one trap per 5 ha, these related weevils must be able to perceive the pheromone traps from at least 100 m away (A.C. Oehlschlager, personal communication). Since the discovery of RPW infestation in Israel, in 1999, various methods of control have been implemented against this pest. The fact that the number of captured beetles has dropped significantly from 325 individuals in 2000 to fewer than 50 in 2002, and that no infested palm trees have been reported since 2002, indicates success in reduction of RPW population level. However, it is difficult to determine the contribution of each control method. An estimation of the relative contribution of spraying vs trapping can be obtained from a major study in the UAE between 1996 and 1998 that included 1,466 farms on which there were >349,000 palms (3). This study examined the effect of spraying alone and of spraying combined with pheromone trapping. A benefit of ∼30% less infestation has been derived from the combined use of spray and pheromone traps compared with spray alone. Mass trapping, as a part of an IPM program using aggregation pheromones, proved useful for the control of some insect pests (see ref. 24), among them some weevils such as the sweetpotato weevil Cylas formicarius (28), the West Indian cane weevil Metamasius hemipterus L. (1), the scarabs e.g. Anomala vitis and A. dubia (27), and the Melanesian rhinoceros beetle Scapanes australis (21). Studies in both the KSA and India indicate that mass trapping of RPW led to a subsequent reduction in adult trapping, suggesting a decline in the local pest population (4,25,26). In the KSA, a reduction in number of trapped individuals was correlated with a decrease in tree infestation (25,26). A similar decrease in capture rates was observed in Costa Rica for a related species, R. palmarum, in oil palm (16,18). The success of mass trapping of the above pests can be explained by the ability of the aggregation pheromone to attract both males and females, while being especially effective in trapping females. The proportion of females trapped in our study was 2–4 females per male and Hallett et Phytoparasitica 33:1, 2005 103 al. (9) found a sex ratio of 3–4 females per male. Since females are the primary target of trapping, it is often debated whether trapping removes young, virgin females with high egglaying potential or old mated females with low egg-laying potential. Our study showed that both virgin and mated females were found in traps. Falero et al. (5) reported further that in India young, gravid females with high egg-laying potential are captured in pheromone traps. Taken together, trapping is predicted to have a major effect on reproductive potential of the population. Male-emitted pheromones are known to attract both sexes (11). This phenomenon of preferential RPW female attraction to the bait requires further study. The differences in trapping can result from a number of factors. One possibility could be a differential response of the sexes to these complex chemical cues. Females attracted to the male and the food bait, gain access simultaneously to both potential mates and host plants. The latter can be used as food source and oviposition sites and as such may be more attractive to females than to males. Females might also be under greater pressure to disperse than males when they leave an infested trunk in a search for suitable food resources and oviposition sites. When the reasons for females outnumbering males in the trap are clarified, they will be used to reduce further the pest reproductive potential in date palms. The present results indicate that pheromone-based mass trapping may provide a tool for controlling RPW females. Controlling females is of special importance in pest control programs and particularly in the case of date palm pests, where breeding sites are difficult to access, females are long-lived and the individual reproductive potential is large. By persevering with the integrated pest management efforts, we expect the pest to be maintained below damage levels in the future. Our studies further suggest that mass trapping as a part of IPM not only reduces the pest population but also assists in the detection of infested trees. However, trap operation is an extremely costly and timeconsuming procedure. Efforts are required to bring down the cost of labor for trapping by further optimizing bait composition, trap design and their spatial distribution. ACKNOWLEDGMENTS We thank Dr. Amos Navon and Mr. Uri Landau for critical comments on this manuscript, Mrs. Shlomit Levsky and Mrs. Miriam Eliahu for maintaining the laboratory population of weevils, Mrs. Dvora Gordon, Mr. Yaakov Nakash, Dany Lavi and Izhak Shema for assistance with weevil monitoring, Mr. Shimon Biton for supervision of chemical control and the late Renéh Modiano for editorial comments. This research was supported by the Israel Ministry of Agriculture Chief Scientist Foundation Grant No. 131-1127-01; and Israeli Palm Growers Association Grant No. 463-0232. This manuscript is contribution 505/03 from The Volcani Center, Bet Dagan, Israel. REFERENCES 1. Alpizar, D., Fallas, M., Oehlschlager, A.C., Gonzalez, L.M., Chinchilla, C.M. and Bulgarelli, J. (2002) Pheromone mass trapping of the West Indian sugarcane weevil and the American palm weevil (Coleoptera: Curculionidae) in palmito palm. Fla. Entomol. 85:426-430. 2. Booth, R.G., Cox, M.L. and Madge, R.B. (1990) IIE Guides to Insects of Importance to Man. 3. New Guinea Records of Economically Important Beetles (Coleoptera). Coleoptera. CABI Publishing, Wallingford, UK. 3. El Ezaby, F.A., Khalifa, O. and El Assal, A. (1998) Integrated pest management for the control of red palm weevil Rhynchophorus ferrugineus Oliv. in the United Arab Emirates, Eastern Region, Al Ain. in: RahmanAl Afifi, M.A. and Al-Sherif Al-Badawy, A. [Eds.] Proc. First International Conference on Date Palms (Al-Ain, UAE), pp. 269-281. 4. Faleiro, J.R., Kumar, P.A. and Rangnekar, P.A. (2002) Spatial distribution of red palm weevil Rhynchophorus ferrugineus Oliv. (Coleoptera: Curculionidae) in coconut plantation. Crop Prot. 21:171-176. 104 V. Soroker et al. 5. Faleiro, J.R., Rangnekar, P.A. and Satarkar, V.R. (2003) Age and fecundity of female red palm weevils Rhynchophorus ferrugineus (Olivier) (Coleoptera: Rhynchophoridae) captured by pheromone traps in coconut plantations of India. Crop Prot. 22:999-1002. 6. Giblin-Davis, R.M. (2001) Borers of palms. in: Howard, F.W., Moore, D., Giblin-Davis, R.M. and Abad, R.G. [Eds.] Insects on Palms. CABI Publishing, Wallingford, UK. pp. 267-305. 7. Giblin-Davis, R.M., Oehlschlager, A.C., Perez, A., Gries, G., Gries, R., Weissling, T.J. et al. (1996) Chemical and behavioral ecology of palm weevils (Curculionidae: Rhynchophorinae). Fla. Entomol. 79:153-167. 8. Hallett, R.H., Gries, G., Gries, R., Borden, J.H., Czyzewska, E., Oehlschlager, A.C. et al. (l993) Aggregation pheromones of two Asian palm weevils Rhynchophorus ferrugineus and R. vulneratus. Naturwissenschaften 80:328-331. 9. Hallett, R.H., Oehlschlager, A.C. and Borden, J.H. (1999) Pheromone trapping protocols for the Asian palm weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae). Int. J. Pest Manag. 45:231-237. 10. Hallett, R.H., Oehlschlager, A.C., Gries, G., Angerilli, N.P.D., Al Sharequi, R.K., Gassouma, M.S. et al. (l993) Field Testing of Aggregation Pheromones of Two Asian Palm Weevils. Palm Oil Research Institute of Malaysia International Palm Oil Congress (Kuala Lumpur, Malaysia), p. A660. 11. Landolt, P.J. (1997) Sex attractant and aggregation pheromones of male phytophagous insects. Am. Entomol. 16:1015-1037. 12. Muralidhadaran, C.M., Vaghasia, U.R. and Sodagar, N.N. (1999) Population, food preference and trapping using aggregation pheromone (ferrugineol) on red palm weevil (Rhynchophorus ferrugineus). Indian J. Agric. Sci. 69:602-604. 13. Murphy, S.T. and Briscoe, B.R. (1999) The red palm weevil as an alien invasive: biology and prospects for biological control as a component of IPM. Biocontrol News Inf. 20:35-45. 14. Nakash, J., Osem, Y. and Kehat, M. (2000) A suggestion to use dogs for detecting red palm weevil (Rhynchophorus ferrugineus) infestation in date palms in Israel. Phytoparasitica 28:153-155. 15. Oehlschlager, A.C. (1998) Trapping of the Date Palm Weevil. Proc. FAO Conference Workshop on Date Palm Weevil (Rhynchophorus ferrugineus) and Its Control (Cairo, Egypt). 16. Oehlschlager, A.C., Chinchilla, C.M., Castilo, G. and Gonzalez, L. (2002) Control of red ring disease by mass trapping of Rhynchophorus palmarum (Coleoptera: Curculionidae). Fla. Entomol. 85:507-513. 17. Oehlschlager, A.C., Chinchilla, C.M., Jiron, L.F., Morgan, B. and Mexzon, R.G. (1993) Development of an effective pheromone based trapping system for the American palm weevil, Rhynchophorus palmarum, in oil palm plantations. J. Econ. Entomol. 86:1381-1392. 18. Oehlschlager, A.C., McDonald, R.S., Chinchilla, C.M. and Patschke, S.N. (1995) Influence of a pheromonebased mass trapping system on the distribution of Rhynchophorus palmarum (L.) and the incidence of red ring disease in oil palm. Environ. Entomol. 24:1004-1012. 19. Perez, A.L., Hallett, R.H., Gries, R., Gries, G., Oehlschlager, A.C. and Borden, J.H. (1996) Pheromone chirality of Asian palm weevils, Rhynchophorus ferrugineus (Oliv.) and R. vulneratus (Panz.) (Coleoptera: Curculionidae). J. Chem. Ecol. 22:357-368. 20. Rahalkar, G.W., Harwalkar, M.R., Rananavare, H.O., Tamhankar, A.J. and Shanthram, K. (1985) Rhynchophorus ferrugineus. in: Pritam Singh and Moore, R.F. [Eds.] Handbook of Insect Rearing. Vol. 1. Elsevier, Amsterdam, the Netherlands. pp. 279-286. 21. Rochat, D., Morin, J.-P., Kakul, T., Beaudoin-Ollivier, L., Prior, R., Renou, M. et al. (2002) Activity of male pheromone of Melanesian rhinoceros beetle Scapanes australis. J. Chem. Ecol. 28:479-500. 22. Rochat, D., Nagnan-Le Meillour, P., Esteban-Duran, J.R., Malosse, C., Perthuis, B., Morin, J-.P. et al. (2000) Identification of pheromone synergists in American palm weevil, Rhynchophorus palmarum, and attraction of related Dynamis borassi. J. Chem. Ecol. 26:155-187. 23. Soroker, V., Nakache, Y., Landau, U., Mizrach, A., Hetzroni, A. and Gerling, D. (2004) Utilization of sounding methodology to detect infestation by Rhynchophorus ferrugineus on palm offshoots. Phytoparasitica 32:6-8. 24. Suckling, D.M. and Karg, G. (2000) Pheromones and other semiochemicals. in: Rechcigl, J.E. and Rechcigl, N.A. [Eds.] Biological and Biotechnological Control of Insect Pests. Lewis Publishers / CRC Press, Boca Raton, FL, USA. pp. 63-101. 25. Vidyasagar, P.S.P.V., Al Saihati, A.A., Al Mohanna, O.E., Subbei, A.I. and Al Abdul Mohsin, A.M. (2000) Management of red palm weevil. J. Plantat. Crops 28:35-43. 26. Vidyasagar, P.S.P.V., Hagi, M., Abozuhairah, R.A., Al Mohanna, O.E. and Al Saihati, AA. (2000) Impact of mass pheromone trapping on red palm weevil: adult population and infestation level in date palm gardens of Saudi Arabia. Planter, Kuala Lumpur 76:347-355. 27. Voight, E. and Toth, M. (2002) Perimeter trapping: A new means of mass trapping with sex attractant of Anomala scarabs. Acta Zool. Acad. Sci. Hung. 48:297-303. Phytoparasitica 33:1, 2005 105 28. Yasuda, K. (1995) Mass trapping of the sweet-potato weevil Cylas formicarius (Fabricius) (Coleoptera, Brentidae) with synthetic sex pheromone. Appl. Entomol. Zool. 30:31-36. 29. Zada, A., Soroker, V., Harel, M., Nakache, J. and Dunkelblum, E. (2002) Quantitative GC analysis of secondary alcohol pheromones: Determination of release rate of the red palm weevil, Rhynchophorus ferrugineus, pheromone from lures. J. Chem. Ecol. 28:2299-2306. 106 V. Soroker et al.