Studies on Rhabdionvirus oryctes: III. Incidence in the Oryctes rhinoceros population of Western Samoa

The viral pathogen Rhabdionvirus oryctes [ROV] was found to be widespread in the population of Oryctes rhinoceros in Western Samoa. About 3% of the larvae and 35% of the adults were infected with ROV. Larval breeding sites more frequently contained ROV-infected insects if the sites were occupied by two broods instead of one and if there was a high density of breeding in the area. Females infected with ROV visited the breeding sites less frequently for egg-laying than healthy females. The male adults, as they increased in age, were found to be more frequently infected with ROV, but the young female adults were more frequently infected than very young or old females. The ROV-infections in adults apparently play a more important role in suppressing the O. rhinoceros population than those of larvae.     

Introducing Baculovirus oryctes Huger into Oryctes monoceros Oliv. populations in Tanzania

A follow-up of a Baculovirus oryctes release into the population of Oryctes monoceros in coconut plantations in Tanzania has been made to clarify important points which were not fully considered in an earlier publication. The low recovery of virus-infected field-collected beetles (29%) suggested that the release of B. oryctes virus was not a suitable method for the control of O. monoceros. The relatively dry conditions in the coconut growing areas were partly contributory since the virus is non-occluded. No significant and sustainable reduction in frond damage was obtained after the virus had established itself in the natural O. monoceros population. The status of O. monoceros as a serious pest of coconut is also revised since the beetle affects young plantations more than older plantations and control methods can be directed at picking up feeding insects by hooking and disposal of breeding sites.     

The Oryctes virus: its detection, identification, and implementation in biological control of the coconut palm rhinoceros beetle, Oryctes rhinoceros (Coleoptera: Scarabaeidae)

In view of the increasing and devastating damage by rhinoceros beetle (Oryctes rhinoceros) to coconut palms in the middle of last century, many efforts were made to find an efficient natural control factor against this pest, which could not be controlled by pesticides. The basic procedures of these monitoring programmes are outlined together with the final detection of a virus disease in oil palm estates in Malaysia in 1963. In extensive laboratory studies, the virus was isolated and identified as the first non-occluded, rod-shaped insect virus, morphologically resembling the baculoviruses. Infection experiments clarified the pathology, histopathology, and virulence of the virus and demonstrated that the virus was extremely virulent to larvae after peroral application. These findings encouraged the first pilot release of virus in 1967 in coconut plantations of Western Samoa where breeding sites were contaminated with virus. Surprisingly, the virus became established in the Samoan rhinoceros beetle populations and spread autonomously throughout the Western Samoan islands. As a consequence, there was a drastic decline of the beetle populations followed by a conspicuous recovery of the badly damaged coconut stands. This unexpected phenomenon could only be explained after it was shown that the adult beetle itself is a very active virus vector and thus was responsible for the efficient autodissemination of the virus. The functioning of the beetle as a 'flying virus factory' is due to the unique cytopathic process developing in the midgut after peroral virus infection. Pathological details of this process are presented. Because of the long-term persistence of the virus in the populations, rhinoceros beetle control is maintained. Incorporation of virus into integrated control measures and successful virus releases in many other countries are recorded.     

Ecology of baculovirus-infected and healthy adults of Oryctes rhinoceros (Coleoptera: Scarabaeidae) on coconut palms in the Philippines

Abstract.

• 1 Males and females of Oryctes rhinoceros (L.), a serious pest of coconut palms, congregate in decaying coconut trunks to mate, oviposit and prepare the wood for the young larvae. A baculovirus disease is often transmitted from beetle to beetle in this environment and transmission to and from larvae probably also occurs.
• 2 Young beetles are mainly found feeding on palms, where they also frequently contract the virus disease, presumably through mating with diseased partners.
• 3 Monitoring beetle populations in the Philippines with attractant traps and by collections from palms showed seasonal fluctuations which were often inversely correlated with the incidence of the virus disease. Disease prevalence matched closely the proportion of females in the population. Possible explanations for this correlation and for the seasonality of the disease prevalence are outlined.

     

Per cent emergent weight: A roadmap to adult rhinoceros beetle,Oryctes rhinoceros,behaviour

Adult rhinoceros beetles, Oryctes rhinoceros L., leave their pupal chambers, take their first flight, and die at well-defined ratios of their wet weight and their adult emergent weight. In addition, the beetles feed in a cyclical manner that is variable with time; however, each feeding event is well defined by a constant ratio of their weight just prior to feeding and their adult emergent weight. The ability to accurately estimate the emergent weight of field collected beetles, and therefore calculate the percentage emergent weight at the time of capture, makes these correlations useful in ecological studies and may be extended to other insects.     

Physical mapping of the genomic DNA of the Oryctes rhinoceros baculovirus, KI.

A non-occluded baculovirus, OBV-KI has been isolated from the insect pest, Oryctes rhinoceros. The viral genome is estimated to be 123 kb, with a G + C content of 43 mol% and no detectible methylated bases. A restriction map of the OBV-KI genome for BamHI, EcoRI, HindIII, PstI, SalI and XbaI has been constructed.     

二疣犀甲室内生物学特性及形态观察

【目的】 对二疣犀甲Oryctes rhinoceros室内生物学特性及形态进行系统观察。【方法】 在室内一定条件下（温度26±1℃, RH 75%~95%, 光周期10L∶14D）以牛粪和锯末混合物（4∶1, m/m）饲养二疣犀甲各虫态, 每6 h观察记录各虫态的形态学特征及其发育情况, 并测量各虫态的重要发育指标, 如体长、 体宽、 体重等。【结果】 二疣犀甲属于全变态昆虫, 一生经历4个虫态, 分别为卵、 幼虫、 蛹和成虫。二疣犀甲卵的发育历期平均为8.88 d, 整个幼虫期平均需156.82 d, 预蛹和蛹的平均发育历期分别为9.45 d和33.75 d, 二疣犀甲完成一个世代需要326~455 d。1龄幼虫体长为4.16 mm, 体重0.64 g, 之后随龄期迅速增加, 至3龄时, 体长为65.66 mm, 体重增加到12.14 g。蛹期平均体长为51.62 mm, 体重为9.72 g。早期羽化的成虫个体较晚期羽化的大, 表现为体长、 体宽、 角长及体重存在显著差异(P≤0.05)。二疣犀甲成虫具有雌雄二型现象, 子代性比(雌∶雄)为1.23∶1。【结论】 二疣犀甲O. rhinoceros是椰子等棕榈科植物的重要害虫, 基础生物学和形态学研究是防控技术研究的基础, 本研究结果可为生产上防治该虫提供理论依据。     

The epizootiology of the baculovirus of the coconut palm rhinoceros beetle (Oryctes rhinoceros) in Tonga

The incidence and distribution of the baculovirus of the coconut palm rhinoceros beetle was determined in Tongatapu, Tonga, 7 years after being first introduced. Surveys showed the virus to be spread throughout the beetle population, affecting 14.6% of breeding sites and over 84% of all adult beetles taken. Counts of damaged palms and of breeding site occupancy indicated that beetle numbers had remained at low levels. It appears that the virus has the potential for long-term control of beetle populations in these habitats.     

薇甘菊甲醇提取物对二疣犀甲生长发育的影响

【目的】探讨入侵杂草薇甘菊Mikania micrantha的利用价值, 及其在棕榈害虫二疣犀甲Oryctes rhinoceros生态防控中的应用前景。【方法】采用浸渍法和室内饲喂法, 研究了薇甘菊甲醇提取物对二疣犀甲取食量、 卵孵化、 化蛹、 羽化及幼虫发育等的影响。【结果】薇甘菊提取物对二疣犀甲具有很好的生长发育调节活性。拒食活性研究结果表明, 在不同供试浓度下, 其对二疣犀甲3龄幼虫均表现拒食活性, 且拒食率与处理浓度呈正相关。薇甘菊提取物处理二疣犀甲的卵后, 孵化率明显降低, 且孵化期延长, 10 mg/mL提取物处理后孵化率仅达66.66%, 孵化期比对照延迟3 d, 同时初孵幼虫死亡率也高达40.43%。采用添加薇甘菊提取物的饲料饲喂1龄幼虫后, 幼虫体重增长减缓, 在处理浓度为10和5 mg/g时, 处理后90 d体重增加量分别为3.83 g和4.53 g, 而对照组体重增加量达到6.87 g。薇甘菊提取物处理老熟幼虫后, 对其化蛹具有抑制作用, 造成化蛹率降低, 化蛹时间延长及蛹的畸形。经薇甘菊提取物处理二疣犀甲蛹后, 成虫羽化率降低, 羽化时间明显延长, 且畸形成虫数量增加, 主要表现为翅无法正常伸展、 虫体瘦小、 无法正常爬行等。【结论】薇甘菊具有开发为生物源昆虫生长调节剂、 并在二疣犀甲防控中应用的潜力。     

The effect of re-release of Oryctes rhinoceros baculovirus in the biological control of rhinoceros beetles in Western Samoa

The Rhinoceros Beetle Project in Western Samoa has developed and successfully applied biological methods to control the rhinoceros beetle, a serious pest of coconut palms, by using two specific pathogens, a baculovirus (Family Baculoviridae), and an entomopathogenic fungus, Metarhizium anisopliae. The application of virus particularly has markedly suppressed the beetle population and helped revive the copra industry. The virus disease had established itself in the wild beetle population several years after its introduction at a level between 30 and 50%. At the same time an increase in beetle numbers and damage to palm trees was experienced. Therefore, a continuous release of virus into beetle-infested areas was proposed. It was argued that, considering the relatively high level of “natural” virus incidence, further releases of virus into the population would be futile. In a combined research and control program, virus was again re-released into the wild beetle population which was already virus infected. The results show that through re-release the virus level can be raised and the number of beetles and consequently the damage can be reduced. The techniques of the control methods are described. The virus release is very easy and cheap; it requires no chemicals, no special equipment, and it is particularly recommended in situations where breeding places are inaccessible or other methods such as plantation sanitation are either impossible or economically impractical. Above all, the methods are absolutely safe from the standpoint of environmental protection.     

An Opportunistic Bacterial Pathogen, Pseudomonas alcaligenes , May Limit the Perpetuation of Oryctes Virus, a Biocontrol Agent of Oryctes rhinoceros L.

Pseudomonas alcaligenes was detected at a high concentration (10 9 -10 10 cells mL -1 ) in the haemolymph of some dead Oryctes rhinoceros grubs collected from its breeding sites in the three southern districts, viz. Alleppey, Quilon and Kottayam of Kerala State, India. In a laboratory colony maintained for production of Oryctes virus, an important biocontrol agent of this major coconut pest, approximately 52% of the grubs succumbed to septicaemia with similar symptoms. The bacterium was found to be a component of the gut microflora of healthy grubs. Occurrence of the viral infection naturally or when induced in the laboratory in the O. rhinoceros grubs, appeared to be one of the biotic stress factors for P.alcaligenes to become an opportunistic pathogen. A preponderance of this bacterial infection in field populations during the periods when natural viral infection in grubs was above average, agrees with this observation. This finding becomes significant as infection by the opportunistic bacterial pathogen, P. alcaligenes , reduces the production of Oryctes virus inoculum in nature and limits the field-perpetuation of this viral biocontrol agent.     

Ecological methods for adult populations of Oryctes rhinoceros (Coleoptera, Scarabaeidae)

ABSTRACT. 1. For comparing assessment methods, O.rhinoceros (L.) populations were monitored in five 30–50 ha plots in southern Luzon, Philippines. No consistent correlations were found between number of beetles caught in traps, amount of palm damage and number of breeding sites. Apparently, plots were too small to account for fast dispersal of beetles.
2. Coconut cap traps baited with ethylchrysanthemumate attracted O.rhinoceros adults searching for breeding sites. Several factors were identified influencing catches but trapping was found to be unsuitable for accurately assessing pest populations.
3. A new method which gives estimates on the monthly number of O.rhinoceros attacks on coconut palms, was tested in the Maldives. Palms are climbed about once a year and the sequence of fronds, the number and the position of beetle cuts are recorded.
4. Reduction with age of the length of three teeth on the fore tibia of O. rhinoceros adults was studied in the Philippines. The data was insufficient to obtain a clear correlation between age and length of teeth.
5. The observations indicated that in the Philippines after leaving their site of pupation, O.rhinoceros adults spend about 5 weeks feeding on coconut palms. This is followed by a period of about 7 weeks in breeding sites and, on occasion, additional visits to palms. With these estimates it was possible to relate palm damage records with numbers of feeding adults.     

Exploration of proteomic biomarkers and digital imaging analysis for Oryctes rhinoceros nudivirus infection

Oryctes rhinoceros nudivirus (OrNV) infects the larval stage of many coleopteran insects; however, the underlying mechanisms and biomarkers of infection are not fully characterised. In this study, an optimal culture condition was developed for OrNV replication and proteomic biomarkers were identified using comparative proteomic analysis. The highest level of viral copy number was observed in Sf9 cells treated with 450 μM of H₂O₂ and 2% foetal bovine serum (FBS). Among the 48 identified proteins, 14 proteins were significantly modulated in 2% FBS and H₂O₂- treated OrNV-infected cells (F2V) as compared with 10% FBS treated non-infected cells (F10M). Network analysis revealed that SLC25A5, VDAC3, PHB2, and ANXA1 act as signature proteins for OrNV replication. Moreover, viral envelope glycoproteins, GRBNV_gp28-like and GrBNV_gp62-like proteins could be used as sensitive diagnostic signatures for OrNV infection. Furthermore, to conveniently identify the OrNV-infection in Allomyrina dichotoma larvae, an image classification model was trained by Google Teachable Machine, which distinguished images with accuracy rates of 91% and 86% for infected and non-infected larvae, respectively, at a learning rate of 0.001. This study demonstrated that Sf9 cell medium treated with 2% FBS and 450 μM H₂O₂ is a permissible culture condition for OrNV replication. Proteomic signatures may be involved in the progression of viral infection. Additionally, a low-cost and non-invasive machine learning-derived digital imaging analysis may improve the prediction of OrNV infection in larvae.     

Structure and function of antennal pore plate sensilla of oryctes rhinoceros (L.) (Coleoptera : Dynastidae)

The antennae of the rhinoceros beetle, Oryctes rhinoceros (Coleoptera : Dynastidae), comprise 4 parts : the scape, the pedicel, a funicle, and a club of 3 lamellate segments. The inner surfaces of the lamellate club segments carry one type of trichoid sensilla, 2 types of sensilla coeloconica, and 3 types of multiporous pore plate sensilla. The total surface occupied by the sensilla on the antenna is 5.2±0.4 mm² in males (mean±SD) and 5.4±0.5 mm² in females. With a measured density of 8665±1254 sensilla per mm² in males and 8952±1642 sensilla per mm² in females, the total number of pore plate sensilla was estimated to be between 45,000 and 50,000. The structure of the 3 types of pore plate sensilla is described. SP1 are the most abundant type of placoid sensilla. They show a convex and rugged plate whose infoldings form a circle of irregular cavities. SP2 sensilla are characterised by a smooth and convex plate, surrounded by a furrow with a ridge. SP2 are localised on a wide band situated along the straight side of the lamella. The plate of SP3 is nearly flat and there is no furrow. SP3 are confined within a narrow margin along the convex edge of lamellae. The 3 types of pore plate sensilla house 2 neurones whose dendrites branch repeatedly under a plate of thin (0.2 μm) cuticle, which is pitted with numerous pores, 40 nm in diameter. Single sensillum recordings with tungsten microelectrodes revealed the firing activity of 2 neurones. These receptor neurones responded specifically to olfactory stimulus. Olfactory receptor neurones tuned to the male pheromone compound, ethyl 4-methyl octanoate, were found in male and female antennae. Other receptor neurones responded to plant volatiles. Morphological and electrophysiological data suggest the absence of a sexual dimorphism in the olfactory organs. The functional organisation of the olfactory organs is discussed in terms of their adaptation to the ecology of O. rhinoceros.     

Structural basis for new pattern of conserved amino acid residues related to chitin-binding in the antifungal peptide from the coconut rhinoceros beetle Oryctes rhinoceros

Scarabaecin isolated from hemolymph of the coconut rhinoceros beetle Oryctes rhinoceros is a 36-residue polypeptide that has antifungal activity. The solution structure of scarabaecin has been determined from twodimensional 1H NMR spectroscopic data and hybrid distance geometry-simulated annealing protocol calculation. Based on 492 interproton and 10 hydrogen-bonding distance restraints and 36 dihedral angle restraints, we obtained 20 structures. The average backbone root-mean-square deviation for residues 4-35 is 0.728 +/- 0.217 A from the mean structure. The solution structure consists of a two-stranded antiparallel beta-sheet connected by a type-I beta-turn after a short helical turn. All secondary structures and a conserved disulfide bond are located in the C-terminal half of the peptide, residues 18-36. Overall folding is stabilized by a combination of a disulfide bond, seven hydrogen bonds, and numerous hydrophobic interactions. The structural motif of the C-terminal half shares a significant tertiary structural similarity with chitin-binding domains of plant and invertebrate chitin-binding proteins, even though scarabaecin has no overall sequence similarity to other peptide/polypeptides including chitin-binding proteins. The length of its primary structure, the number of disulfide bonds, and the pattern of conserved functional residues binding to chitin in scarabaecin differ from those of chitin-binding proteins in other invertebrates and plants, suggesting that scarabaecin does not share a common ancestor with them. These results are thought to provide further strong experimental evidence to the hypothesis that chitin-binding proteins of invertebrates and plants are correlated by a convergent evolution process.     

The Effects of Mortality and Influence of Pheromone Trapping on the Infestation of Oryctes rhinoceros in an Oil Palm Plantation

The infestation levels of O. rhinoceros were investigated in the oil palm trunk heaps in three replanting blocks (Blocks A, B and C) at Sepang, Selangor, Malaysia. These blocks had different densities of pheromone trapping: high (11 traps per ha, Block B), normal (1 trap per 2 ha, Block C), while no pheromone trapping was conducted in (Block A. Without pheromone trapping, the infestation levels of O. rhinoceros can reach a maximum density of between 25 to 50 individuals per m² (IPMS). The O. rhinoceros population was still detected in the heaps up to more than two years (at 26 months after replanting). With high density trapping, infestation levels were maintained below 10 IPMS and was not detected in the heaps after a period of 16 months of replanting. In the normal trapping density, the population was also maintained below 10 IPMS but had sustained itself in the heaps for up to 24 months. The mortality factors associated with the larval stages sampled within these replanting blocks was determined by visual symptoms with subsequent verification with microbial analysis. The analysis was narrowed down to detect only bacteria (Bacillus thuringiensis and B. popillae), virus (Oryctes virus) and fungus (Metarhizium). In Block A, the population of O. rhinoceros in the trunks was reduced drastically at 14 months after replanting (MAR), which could be due to the high mortality (88%) of the third instar larvae, 3 months earlier. In Block B, the percentage mortality for the larval stage was always highest at the third instars (between 21–82%). In Block C however, the mortality of the third instars was low, never exceeding 35%. In these sampling blocks, the infection of Metarhizium seem to be less dominant compared to virus or bacteria The k factor analysis indicates density dependence among the third instar larvae had contributed to the change in its population density in Block A. Therefore, with proper manipulation of pheromone traps and targeted application of disease agents (i.e virus, fungus and bacteria), the population of O. rhinoceros can be managed more effectively in an oil palm replanting.