Damage Intensity and Geographic Distribution of Oryctes rhinoceros on Coconut in Rote-Ndao, East Nusa Tenggara Province, Indonesia

Oryctes rhinoceros poses a significant threat to coconut plants in several coconut-producing nations, including Rote Ndao District. Recognizing the distribution and severity of crop damage caused by this pest in Rote Ndao Regency is crucial for preemptively preventing pest outbreaks and evaluated the extent of the damage. This study aims estimate the damage intensity and to identify the geographic distribution of O. rhinoceros in the Rote Ndao District. Conducted through a mobile across central coconut production areas in every sub-district of Rote Ndao Regency, the study examined variables such as damage symptoms, damage intensity, and spatial data represented coordinate points. Analysis of damage intensity data involved calculating average values. These coordinates were then overlaid with administrative data for Ndao Regency to create a map illustrating the distribution of damage severity. The results showed that O. rhinoceros attack symptoms on coconut plants were in ninety-five villages in ten sub-districts in Rote Ndao Regency. This pest is categorized as a pest important because the damage intensity map was found in ten sub-districts in Rote Ndao Regency. Average damage intensity is 8.99%. Multiple approaches, including sanitation environmental, sex pheromones, and entomopathogenic fungi, are employed to manage this pest effectively.


Introduction
The coconut rhinoceros beetle (CRB), Oryctes rhinoceros (Linnaeus, 1758), is a scarab beetle that is a major pest of coconut (Cocos nucifera L.), oil palm (Elaeis guineensis Jacq.), and many other palm species Oryctes rhinoceros (Coleoptera: Scarabidae) known as the coconut weevil is an important pest on the coconut plant [1,2,3,4,5].The beetle is believed to be native to Southeastern Asia, but today has spread eastward to the Pacific and westward to India, islands in the Indian Ocean, and the tropical regions of Africa [6].In Indonesia, the coconut weevil is an important pest [7], on oil palm [3,8,9,10,11] and deep coconut.The damage caused by this pest can reach 5.5-9.1% [5] but under suitable.1346 (2024) 012015 IOP Publishing doi:10.1088/1755-1315/1346/1/012015 2 conditions the damage on leaves at all growth stages even the damage can reach 20-30% [12,13].This pest damages coconut leaves at all growth stages.In the India and Southeast Asia, this pest attack causes a yield loss of 10% [14], making the pest one of the most destructive pests of coconut and oil palm, especially where both palms are cultivated traditionally such as in Rote-Ndao District of the Province of East Nusa Tenggara (ENT) and most of other areas in Indonesia.
Rote-Ndao District consists of one medium-sized island of low elevation and many other surrounding small islands in the climatically driest province of Indonesia [15].In such dry conditions, coconut, together with borassus palm Borassus flabelifer, provides alternative staple food for local communities.In addition, coconut also serves as the source for animal feed and traditional cooking oil, as well as an importance source of income by selling copra, the dried coconut meat.However, copra production decreased 12.33% in 2018-2019, further decreased 11.60% in 1920-1920, and although much smaller, decreased by 1% in 1920-1921 [16].This decrease in copra production could be due to infestation by pests, most likely CRB, considering the dry climate of the district is suitable for the population growth of the beetle [17].Coconut has an even more far-reaching role as it is under its shade that the white sand beaches behind the clear water teeming with marine life and surfable waves that have made the district more attractive as one of the top tourist destinations in Indonesia [18].
Considering the beetle as the possible cause of the decrease in copra production as described above, a preliminary survey was carried out and found symptoms of damage caused by the beetle found in the villages of Nembrala and Batutua.Owing to the nature of the damage observed in the two villages, it was suspected that the beetle had spread to other villages in the district.The district's low elevation, high temperature, high wind speed, and high rainfall during the short rainy season facilitate the population growth and geographic expansion of the beetle [17], causing widespread damage on coconut in the island district where coconut is both an important source of both subsistent livelihoods and household income.Therefore, an extensive survey was conducted with aims to estimate the intensity of coconut damage and to determine the geographic distribution of the pest.

Research Method
The study was carried out in 2022 in ten sub-districts located in Rote-Ndao District, which represents the southernmost district and is located in the driest climate zona in Indonesia.In all districts, coconut is cultivated for different purposes by the local communities.The research methodology uses a combination of surveys and farmer interviews.The survey was conducted in all villages with have coconut plantations in each sub-district.In each sub-district, villages with large coconut plantations were sampled randomly.From each village, ten farmers were sampled for interviews.The assessment of damage to interviewee's coconut plants involved evaluating ten coconut plants per individuals.These coconuts were chosen randomly with a planting of 30-40 meters apart.

Data Collection
Interviews were conducted to obtain data on the age and varieties of coconut owned, cultivation practices, and pest management carried out by each interviewee.Symptoms of damage caused by CRB was observed on mature as well as young individuals on open leaves, growing points, and trunks, respectively.However, the damage intensity of each coconut individual was estimated visually in the form of the percentage of damaged by visually assessing in the plant coconut.Spatial data were taken along with the attribute data by taking altitude and longitude coordinates using a GPS receiver.
Photographs was taken to document symptoms of damage on each part of the observed coconut individual and on the egg, larva, and adult of CRB found.Search for eggs, larva, and adult CRB was carried out on the around coconut plantations.Samples of eggs, larva, and adults of CRB found were collected by placing in jars containing HCN for further drying and macroscopic observations in the laboratory.

Data Analysis
Data on the intensity of damage to coconut plants is calculated using the non-absolute damage formula, namely: Information: I = damage intensity; n = number of plants in category v; v = the scale value of each attack category; Z = the scale value of the highest category; N = the number of coconut plants observed.Attack category scores and attack criteria are presented in Tables 1 and 2. The average value of damage intensity data is calculated and then interpreted descriptively.Attack symptoms are shown in pictures and described.The results of field coordinate data collection were then overlaid with data from the administrative area of Rote Ndao Regency to illustrate a map of the distribution of attack intensity.

General description of coconut plantations in Rote Ndao District
The observation results show that ten sub-districts in within Rote Ndao Regency engage in the cultivation of coconuts trees.Among these sub-districts South Rote, Southwest Rote, West Rote, Southwest Rote, Northwest Rote, Central Rote, and Ndao Nuse.Nearly all the villages in thesesubdistrict have coconut plants.
Typically, coconuts are grown in residential yards, gardens, and along the coastline, with a spacing of 1.5-3 meters between trees.The coconut variety predominantly cultivated is the tall variety, by characterized by its vibrant green leaves, a height ranging from four to seven meters above the ground, and green-hued fruit.In general, these trees are more than two decades old and continue to bear fruit.Our observations and conversations with the local community suggest that there hasn't been any effort to rejuvenation of these coconut crops, despite the fact that they remain a source of income through copra production.
Agronomic practices such as fertilization and irrigation are seldom carried out by farmers, because this coconut variety does not demand extensive water.Pest control measures like sanitation, pruning, and pesticide application are infrequently undertaken.Pruning was never done because this variety has a plant height of more than two meters.Adult O. rhinoceros attack primarily on young shoots, unopened leaves, and the base of coconut leaves (Figure 1a), particularly in the case of young coconut plants (Figure 1b), and leading to Vdamage on coconut trees (Figure 1c).The mandible of O. rhinoceros make hole in the coconut trunk trees (Figure 1d).Both imago and larval form of the insect were discovered in heaps of soil around the coconut plantations (Figure 2a and Figure 2b).Infested coconut trees serve breeding ground for O. rhinoceros (Figure 2c).Male and female adults are distinguished by their mandibles.The mandibles of the male adult move forward from the mouthparts.
Distinguished between male and female adult coconut beetles can be accomplished by examining their mandible.In males, the mandibles feature a snout-like shape (Figure 3a).The snout is sturdy and strong, enabling it to create openings coconut trunks, excavate the soil, and accumulate litter as a substrate for egg-laying and larval development.On the other hand, mandible female does not shape a snout-like (Figure 3b).Elytra black, Additionally, their elytra are black.The mobile monitoring result conducted in the coconut plantations within the Rote Ndao District revealed the presence of symptoms indicating an infestation by the coconut beetle O. rhinoceros.The average level of damage was measured at 8.89%, falling into the category of a mild attack (Figure 4 and Table 3).This pest was found to be widespread across ten subdistricts in Rote Ndao District, namely South Rote, Northwest Rote, Central Rote, Pantai Baru, East Rote, Southwest Rote, West Rote, Landu Leko, Ndao Nuse, and Lobalain.In Figure 4, one village in Northwest Rote District, the attack intensity was classified as a moderate category, with average damage intensity for coconut plants reaching 32.22%.[13,19,20,21,22].Coconut beetles damage coconut plants by tunnelling into coconut leaves, thus diminishing the photosynthesis process, ultimately resulting in stunted plant growth.If the growing point is damaged, it can lead to the demise of plant, thereby reducing production [13] Intensity of damage to coconut plants caused by adult coconut beetles in East Rote and Central Rote Districts is relatively lower compared to other sub-districts.The average intensity of damage in these districts stands at 3.17% and 2.59% (Table 3).This suggests that the adult population is likely lower, as their capacity to inflict damage is limited due to the lower number of host plants.Observations reveal that the population of coconut plants does not exceed ten trees around the sampling coordinate, and the planting distance exceeds twenty meters.Another study has demonstrated that low coconut plantations also result in a reduced coconut beetle population [23], consequently reducing the number of infested plants and lowering the intensity of damage.
In South Rote, West Rote, Northwest Rote, Southwest Rote, Ndao Nuse, and Lobalain, the intensity of damage to coconut plants ranged from 8% to 15%.This area has a high population of coconut plants, there are more than forty trees around the sampling location, with a planting distance is approximately 2 to 3 meters.This indicates the presence of a larger adult population in the ecosystem.With a more abundant host plant population, the number of piles of coconut litter increases, providing a suitable environment for larvae and pupae to develop and take shelter.This coconut plant is located close to the coastline, close to residential areas, close to close to horticultural fields, and there is a buildup of inorganic and organic waste around it, making it a potential breeding ground for female insects to lay eggs.Adult insects usually deposit their eggs near decaying organic material such as sticks, piles of rubbish, garbage, or sawdust [24,25].This environment also functions as a place for larvae and pupae to complete their life cycle until adulthood.
Other potential breeding sites for coconut beetles included piles of cow and goat manure, as well as various organic materials.At the time of observation, the research team also found many goats at almost all observation points, especially in the Districts of West Rote, South Rote, Northwest Rote, and Southwest Rote.It is suspected that piles of goat droppings serve as a suitable medium for adult beetles to lay eggs, enabling larvae and pupae to develop within these heaps.Oryctes rhinoceros were discovered in these piles, with instar three larvae constituting 72.39% of the population [7].
While are no dedicated coconut plantations in Rote Ndao District, the local community cultivates coconuts trees in various locations, including their yards, along the coastline, and around horticultural crops, totaling over fifty plants.With a significant number of coconut plants and inadequate sanitation practises within the ecosystem, improperly managed household waste becomes a potential source for coconut beetles to complete their life cycle.Additionally, decaying palm tree trunk can also serve as a medium for adult beetles to lay eggs and for other stages of their life cycle progress.
Other hosts of this pest are banana plants and yellow flamboyant (Peltophorum pterocarpum) [23,26] and several other species of plants such as pineapple and sugar cane [26], areca nut, snakefruit, ornamental coconut, papaya, sugar apple, and taro [27].In India, rhinoceros beetles have damaged banana plants and damage caused can reach 4-20% of coconut plants intercropped with banana plants [22].
During observations, no symptoms of O. rhinoceros attack were found on banana plants, but it is suspected to be a breeding medium for the larval and pupal stages around the banana plants, there are lots of piles of organic material.Pupae that succeed in becoming imago will most likely migrate to nearby coconut plants.In general, residents of Rote Island cultivate bananas between coconut plants.
Another host of O. rhinoceros is Borassus flabellifer L. The same attack symptoms are also found in this plant.This commodity is also a superior commodity for the people of Rote Ndao because it is the raw material for palm sugar and plate sugar as a substitute for granulated sugar.Therefore, we need to be careful of this pest so that there is no explosion in the pest population which causes severe damage or puso to superior commodities such as coconuts, palm leaves, and bananas.The three plnats become hots for O. rhinoceros found in the field, so it is recommended that coconuts, palm trees, and bananas not be planted on the same ecosystem.
The population development of O. rhinoceros is also supported by the influence of climate change.Predictions suggest that by 2080, due to climate change (e.g., an average air temperature increase of 26,81%; a diurnal range increase of 11.33%, and an elevation increase of 4.49%), this pest will pose a significant threat to economically valuable host plants [28].With the increasing adult population of O. rhinoceros, the damage to coconut fruit production will decrease [25].Therefore, monitoring needs to be carried out regularly by farmers and observers of Plant Destruction Organisme to obtain information on the development of the intensity of damaged O. rhinoceros and the factors that influence it.This information becomes a reference for preventative and pest control measures.Control of O. rhinoceros is achieved through various technologies, including the use application of insecticides, sanitation of the surrounding environment, and the of biological control agents such as Metarhizium anisopliae and Oryctes rhinoceros nudivirus (OrNV) [14].Larvae can be controlled using seed extract Azadiracta indica and Annona squamosa flour [29,30].

Conclusion
Oryctes rhinoceros is a significant pest in coconut plantations within Rote Ndao Regency, as 95 villages in 10 subdistrict have been observed exhibiting symptoms of attacks by this pest.The average damage intensity is 8.99%, categorizing it as a minor attack.It is imperative to address this to prevent potential outbreaks, particularly since it serves as a source of food, shelter, and breeding grounds for larvae, pupae, and adult stages.

Figure 4 .
Figure 4. Distribution map of damage to coconut plants caused by Oryctes rhinoceros.

Table 1 .
Coconut crop damage scores caused by Oryctes rhynoceros Tabel 2. Category of Oryctes rhynoceros attack on coconut Attack intensity (

%) Attack criteria
Symptoms of Attack and Distribution Map of Intensity Damage to Coconut Plants by Oryctes rhinoceros

Table 3 .
Damage intensity of Oryctes rhinoceros on coconut plants in Rote NdaoOryctes rhinoceros is regarded as an important pest in Rote Ndao Regency, as it was detected at all observation sites.The damage inflicted by this pest was generally categorized as mild across all villages, except for Modosinal Village in North West Rote District, where the intensity of O.rhinoceros infestation was considered moderate.In several countries, this pest is recognized as a noteworthy and widespread issue concerning coconut plants, necessitating vigilant monitoring