Population and attack of bagworm pests in smallholder oil palm plantations in Tenggulun Sub District, Aceh Tamiang District, Aceh

Bagworms are leaf-eating insects that are quite greedy and difficult to control because these pests hide in their bags. This pest control needs to be done especially on immature plants. This research aims to determine the dynamics of bagworm populations in immature oil palm plants and the percentage of bagworm attacks in smallholder oil palm plantations with different management. This research was carried out by direct observation of bagworms on Smallholder Oil Palm Plantations in Selamat Village and Tenggulun Village. In each village, 2 observation locations were determined and 25 plant samples were selected from each observation location. Dead bagworms are collected to determine the cause of death. The results of the research found 3 species of bagworms at the research location (Mahasena corbetti, Metisa plana and Cremastopsyche pendula). The most commonly found bagworm species is Mahesa plana. Mahasena corbetti is a priority to control because its attack level is in the medium category. Furthermore, the percentage of bagworm attacks ranges from 38-76%. The bagworm population in Selamat Village is lower than in Tenggulun Village, this is because oil palm farmers in Selamat Village have implemented integrated pest control methods in managing their oil palm plants, (utilizing natural enemies/predators, manual eradication of bagworm pests and trunk injection.


Introduction
Oil palm (Elaeis guineensis Jacq) is a palm oil producing plant which is the main source of economic income for the community in Aceh Tamiang District.The area of smallholder oil palm plantations in Aceh Tamiang District in 2020 was 21,956 ha with a production of 251.09 thousand tonnes of Fresh Fruit Bunches (FFB) and productivity of 11.43 tons of FFB per hectare [1].If we look at the area of land with production, the productivity is very far from the total productivity that farmers should get, where under optimal conditions, oil palm productivity can reach 30.6 tons of FFB per hectare [2].
According to [1] the high need and competition in utilizing natural resources, forces humans to utilize these natural resources beyond their abilities without paying attention to conservation actions, causing damage to limited natural resources.Like during the rainy season, the water discharge will suddenly rise and cause the water to overflow.On the other hand, during the dry season, the water discharge decreases drastically resulting in water shortages.This is due to the large fluctuations in river discharge that vary during the rainy season and dry season.
One of the reasons for the low productivity of oil palm is because the plants are no longer productive.Oil palm productivity will decrease with age after approximately 18 years [3].To overcome this problem, since 2019, the Aceh Tamiang Regency Government, in collaboration with the Ministry of Agriculture of the Republic of Indonesia and the Palm Oil Plantation Fund Management Agency (BPDPKS) has launched programs People's Palm Oil Rejuvenation (PSR), partnership development and ISPO certification.
The implementation of this program is in partnership with several oil palm plantation cooperatives/farmer groups in Aceh Tamiang Regency.The registered PSR area will reach 9,624.15hectares by the end of 2022.Of this amount, 6,455 hectares have been replanted.Selamat and Tenggulun Villages, located in Tenggulun District, are one of the villages that receive assistance from the PSR Program.By 2022, the area of smallholder oil palm plantations that receive assistance will be 960 ha.
After the PSR program was running, a new problem emerged with the high number of pest attacks by Palm Oil Leaf Eating Caterpillars (UPDKS) consisting of fireworms, bagworms and hairworms which attacked the leaves of immature oil palm plants massively but did not directly cause death to the plants.Of the three types of UPDKS, bagworms are difficult to control because they have a defense structure in the form of a bag.The three main species of bagworms that are pests of oil palm are Metisa plana Walker, Pteroma pendula Joannis, and Mahasena corbetti Tams [4].
Damage to oil palm leaves by bagworm pests will disrupt the photosynthesis process so that the supply of assimilate for fruit development is reduced [5].Damage to the leaves can also cause stress in oil palm plants so that they tend to form male flowers [6].
In controlling bagworm pests, it is necessary to apply the principles of Integrated Pest Management (IPM) which are safe for the environment.The aspects considered in implementing IPM principles are the implementation of healthy cultivation, regular monitoring of pests and diseases, the use of natural enemies, and farmers as experts on their land.In order to successfully control bagworm pests, it is necessary to first study the type of bagworm that is attacking so that control measures can be determined to be taken.The aim of this research is to determine the dynamics of the bagworm population in the immature phase of oil palm and the factors causing their death.

Location dan Times
This research was conducted in Tenggulun sub-district, Aceh Tamiang Regency, Aceh Province.This research was carried out for three months (June to August 2023).

Bagworm Sampling
Observations were made in 2 villages (Selamat and Tenggulun ) on oil palm plants in the immature plant (TBM) phase.The Bagworm data collection is collected once every two weeks during the period June to August 2023.The sampling method is carried out by a survey using the Systemic Random Sampling Method, namely collection is carried out sequentially at certain intervals.Starting from the plants in the two outer rows as the starting point of sampling, then proceed to the next two rows by stepping over one row after the initial row of samples.For each observation period, 25 oil palm trees were randomly selected.Observations were made destructively by cutting the 9th and 17th fronds.

Species and Numbers of Bagworm Pests
Observations of the species and number of pests were carried out on oil palm plants that have symptoms of high bagworm attacks.The types and quantities of the calculated bagworm pests will be used as initial data is then collected to be made into one data piece, namely, data on the type and number of whole pests.

Attack Rate
The level of of bagworm attack was calculated based on the number of pests found on the stems of the sampled oil palm plants.The categories of bagworm attack levels on immature oil palm plants (TBM) can be seen in table 1.

Percentage of bagworm attacks
The percentage of bagworm attacks is the percentage of the number of plants attacked by bagworm pests over the total number of plants sampled.The percentage of bagworm attacks is calculated using the following formula: Based on the formula above, the P value represents Percentage of attacks by bagworm pests (%), the n value represents the number of plants attacked by bagworm pests and, the N value is the total plants observed.

Data analysis
Data analysis was carried out descriptively quantitatively on the number of trees attacked, number of pests, attack level categories and percentage of bagworm attacks at the research location.

Species of bagworm pests and number of trees attacked
As a result of observations of the types of bagworms, information was obtained that there were 3 types of bagworms that attack oil palms at the research location.These three types of pests were found in both villages at the observation locations (table 2).Description: SLM = Selamat Village; TGL = Tenggulun Village.
Based on table 2, it can be seen that the Metisa plana type pest mostly attacks oil palm plants at the research location.This can be seen from the high number of pests found during field observations.Of the 100 sample trees, 34 trees were found to be attacked by M. plana.Palm oil plantations in Tenggulun Village were attacked more by M. plana than in Selamat Village.
In Indonesia and Malaysia, several species, such as P. pendula Joannis, 1929), M. corbetti Tams, 1928, and M. plana Walker, 1855, were found to be important pests in oil palm and forestry crops [8; 9].M. plana is the most serious and dominant pest on oil palm plants, followed by Pteroma pendula and Mahasena corbetti.This attack results in huge economic losses [10; 11]

Attack rate
The results of observing the number and categories of bagworm pest attacks on samples of immature oil palm fronds (TBM) at the research location are presented in table 3. From table 3, it can be seen that in the two research location villages, M. plana pests were mostly found attacking immature oil palm plants.This pest eats the tops of the leaves, causing dry bite marks and holes.Observations of bagworm pests at 2 points in the same garden were carried out by counting the number of living larvae.The characteristics of live bagworm larvae can be seen from their feeding activities and larval movements.The bagworms found in each plant sample were dominated by late instars with bag sizes of around 2-4 cm.However, based on the attack category based on critical populations, the number of M. plana attacks is still in the light attack level category.On the other hand, although the number of M. corbetti that attacks immature oil palm plants in the research location is less, if seen from the level of attack, it is in the moderate to heavy category.
When the bagworm eggs hatch, it starts looking for food by scraping the top surface of oil palm leaves [12].The scratched surface dries out and forms a hole.As a result, severely damaged leaves cause the lower and middle crown to appear gray.Most of the leaf tissue is used for body maintenance and growth (66.8%) and the other 33.2% is used for making bags [13].
The bagworms found were in varying phases from early instar to late instar.This condition affects the presence of bagworms which are always present at all times.According to [14], bagworm pests do not have a specific breeding season, because this species can breed throughout the year.

Percentage of bagworm attacks
The highest percentage of bagworm attacks was found in Tenggulun Village at 76% (table 4).Late control of bagworm pests is the trigger for the high incidence of pest attacks.This can be seen from the large number of plants attacked and the number of bagworms found.Based on table 4, the low population of bagworms in Selamat Village is due to the presence of bagworm predators in the form of Oecophylla smaragdina, jumping spiders and Sycanus dichotomus.These three predators actively prey on oil palm leaf-eating caterpillar larvae, this makes them act as important predators that are able to kill and prey on almost all lepidoptera larvae in oil palm plantations.
Sykanus sp has a high ability to search for find prey, has a long imago lifespan (±2 months), and has a long rostrum making it easier to attack various larvae compared to other predatory insects [15].Predators such as Sycanus sp.requires a lot of prey in its life cycle to fulfill its nutrition.So one predator individual can kill more pests than one parasitoid individual.Predators, both female and male, and also in their immature phase can search for and obtain prey [16].
Then, oil palm farmers in Selamat Village have also implemented control using Trunk Injection.Trunk Injection is an effective application for controlling and monitoring bagworm disease in oil palm plantations.Finally, oil palm farmers in Selamat Village also control bagworms by collecting larvae and adult worms and then killing them by burning them.
The application of Trunk Injection in oil palm plantations turned out to give a good impression on controlling and monitoring bagworms in terms of plant growth and increasing yields.This method is used for heavy and medium category attacks with spot attack patterns and/or overlapping pest stages, including caterpillar, egg, imago phases) and/or for isolation.Trunk injection uses a drilling machine and systemic chemical insecticides.The insecticide used contains the active ingredient Acephate at a dose of 18g/tree.This method is relatively safe because it does not kill natural enemies and pollinate beetles.
They obtained this ability thanks to training in sustainable palm oil cultivation.Oil palm farmers in Selamat Village who join the Palma Lestari Cooperative receive a mentoring program initiated by a multi-stakeholder forum called the Center for Sustainable Plantation Excellence.This institution has started mentoring activities for independent palm oil farmers in Aceh Tamiang Regency since 2020.And in 2023, the Palm Oil farmer group in Selamat Village will become the first independent farmer group in Aceh Province to receive dual ISPO-RSPO certification.
According to [17] for oil palms, technique Trunk Injection has been applied without problems and with high efficiency against various pests.Its use is either to deal with abnormal pest breeding, or to implement an integrated pest control program where the main purpose of injection is preventative.With long-lasting insecticides, the number of treatments can be reduced significantly.Insecticides given by injection can protect palms with just two or even one treatment per year.

Conclussion
There are three species of bagworms that attack people's oil palm plants at the research location.The Mahesa plana is the most commonly found bagworm.Even though the number is the largest, in terms of the attack level category, the Mahasena corbetti is a bagworm pest whose attack level category is included in the medium category and is the first priority to be controlled.Furthermore, the percentage of bagworm attacks ranges from 38-76%.Of the three parameters assessed, Selamat Village is the location with the lowest level and percentage of bagworm attacks.This matter because farmers have received training and guidance regarding integrated pest control methods to control pests in oil palm plants.Farmers in this village have used chemical methods (Trunk Injection) to control bagworm pests.
P = n/N x 100% Description: P = Percentage of attacks by bagworm pests n = Number of plants attacked by bagworm pests N = Number of plants observed

Table 1 .
The categories of bagworm attack levels on immature oil palm plants (TBM).

Table 2 .
Results of observations of the type of bagworm and the number of oil palm

Table 3 .
The categories of bagworm attack levels on immature oil palm plants (TBM)

Table 4 .
Percentage of bagworm attacks