Incidence of the tussock moth attack: Issue, crop damages and management strategies to support sustainable oil palm plantation

The problem of insect pests in the palm oil industry has shown a considerable shift during the second decade of the twenty-first century due to ecosystem and technological changes. The interaction between palm oil as a host plant and the behaviour of insect pests undergoes an adaptation process. Defoliating insects of oil palm in Central Kalimantan, at certain times, experience explosions, such as the tussock moth species Dasychira inclusa (Walker, 1856) and Calliteara horsfieldii (Saunders, 1851). Several factors led to the tussock moth explosion, including environmental factors, human resources, and management strategies. The percentage of crop damage caused by the tussock moths from mild, moderate, severe to very severe categories was 43.48%, 15.57%, 21.74% and 10.87%. The tussock moth outbreak is giving rise to restoration efforts to keep the ecosystem balance in the landscape back to normal. Efforts to maintain ecosystem balance through regular and accurate monitoring, introducing and withdrawing beneficial insects, and planting proper plant vegetation. This action is one of the keys to dealing with small pest outbreaks or significant pests. Ultimately, a diversified ecosystem provides more crop protection opportunities.


Introduction
Palm oil is considered an essential commodity in encouraging the Indonesian economy.The increase in demand for palm oil globally impacts increasing production.According to data from the Indonesian Directorate General of Plantations, oil palm plantations in 2022 will cover 15.38 million hectares of land with a total production of 48.24 million tons [1].Palm oil is economical because its productivity per hectare is higher than other vegetable oils, contributing to 70% of total vegetable oil imports.[2].The Indonesian government has encouraged palm oil expansion by providing policy support to large and small-scale producers.The increasing plantation area every year will impact production; on the other hand, it will cause environmental problems, such as the emergence of new types of pests.The phenomenon of new pests can occur due to disturbance in the old habitat, so the pests look for new habitats to survive.This phenomenon will appear in plantations with a monoculture system, such as oil palm plantations.[3] Pests in oil palm plantations are still dominated by insect groups, especially from the order Lepidoptera [4].The tussock moth is one of the leaf-eating caterpillars and is a severe pest of oil palm [5].The tussock moth usually attacks oil palm plants in nurseries, from immature plants to mature plants.Wei et al. [6], reported that tussock moth attacks caused damage to oil palm leaves.Several researchers have previously reported the presence of tussock moths on oil palms.The tussock moth said to attack oil palm plants include Calliteara horsefieldii Saunders [5,7,8,9]; Pseudoresia desmierdechenoni [10]; Orygia sp.[11]; Dasychira inclusa Walker [7,12,1314]; and Dasychira mendosa [15].If pest monitoring activities do not go well, this caterpillar species population can increase fast because it has a short life cycle with high reproductive ability [16].
The loss estimation on the palm oil yields due to the above pests was 20%-30%, extending to three years after the attack [17].Leaf-eating caterpillar attacks cause long-lasting problems, with explosions 1346 (2024) 012014 IOP Publishing doi:10.1088/1755-1315/1346/1/012014 2 occurring from time to time.The impact of attacks by leaf-eating caterpillars causes up to 100% leaf damage on adult plants.In one year, the first attack will reduce production by 73%; in subsequent episodes, production could decrease by up to 93%.Pahan, 2008 in [18].In the first year, yield loss can occur due to a decrease in bunch weight, while in the second year, it is generally influenced by a higher ratio of male flowers [4].The tussock moth can also cause health problems in humans through inflammatory reactions that occur due to exposure to setae [19,20].
Management of the tussock moth in oil palm plantation ecosystems can be done by optimizing with implementation of an integrated pest management [21].Natural enemies are organisms found in oil palm plantation ecosystems whose presence can weaken, kill and reduce the reproductive phase of insect pests.Integrated Pest Management is an effective and environmentally sensitive approach to reducing tussock moth attacks, such as biological, physical, mechanical, and chemical controls, especially by spraying bioinsecticides Bacillus thuringiensis [22,19,23], and chemical insecticides, spray monocrotophos [6], carbaryl, permethrin, asephate [6,19].These synthetic chemicals have broad target effects that make them dangerous when applied to oil palm plantations.
In September 2022, there are indications of damage to oil palm plants caused by the tussock moth.The tussock moth occurs in palm oil plantations in the Manuhing sub-distric of Gunung Mas Regency, Central Kalimantan.There needs to be more information on explosion incidents, the extent of tussock moth damage to oil palms, and control in Indonesia.This research aims to identify the type, explosion occurrence, damage level, and tussock moth control in oil palm plantations by prioritizing ecosystem services in supporting the sustainability of the palm oil industry.

Methods
The research was carried out in September 2022 at the oil palm plantation in the Manuhing sub-district of Gunung Mas Regency, Central Kalimantan.The tussock moth was observed in a mature oil palm block with indicated tussock moth attack (± 29 Ha).

Sampling and Observation
The observation of attack incidents and crop damage due to attacks by the tussock moth by observing directly in oil palm plantations.The observation location on oil palm plantations attacked by tussock moths in the Manuhing sub-district.Observations were conducted on sample plants in systematic random sampling (following "Routine Detection" standards for leaf-eating caterpillars in oil palm plantations).Observations of the tussock moth population started from east to west, from row 3, then rows 13, 23, 33 and others, with intervals of ten rows of plants in the block.The first census line (line 3) determines three census points: the 5th, 15th and 25th trees or every ten trees out of 34 oil palm trees in one planting row.Next, in the second census line (line 13), three further census points are determined using the same pattern in every ten lines.And so on, determined systematically.Determination of frond samples at the enumeration point can be seen from the fronds that show the most severe damage symptoms due to tussock moth attacks.All the tussock moths found were counted and recorded in observation form.
Measuring the intensity of the tussock moth attacks by calculating the percentage of oil palm plants that were attacked, with symptoms of damage to the leaves.Next, observe the level of crop damage through "Special Detection" by purposive sampling in oil palm areas that show symptoms of leaf damage due to the tussock moth attacks.The scale for the level of oil palm damage follows the Natawigena method [24].The system for assessing plant damage due to tussock moth attacks was carried out visually using the assessment criteria in Table 1.Calculating the intensity of crop damage using the formula: (1) N Remarks: P = damage intensity (%), n = number of damaged crops N = number of crops observed Meanwhile, calculating the damage intensity of the leaves or leaf midrib using the following formula: (2) N x V Remarks: I = damage intensity (%), ni = number of the leaves damaged from each attack category vj = the scale of each attack category, Z = highest scale attack category N = number of the leaves observed

The tussock moth identification
We collected and placed tussock moth larvae in plastic containers and then identified them.Identification was carried out based on the character of the tussock moth (Lepidoptera: Erebidae), including tufts of hair called seta (seta, singularly) or tussocks along their bodies, which are their most distinctive feature.Some species have distinctive markings or patterns on their bodies as well.Observations and identify the morphological characteristics of pests.

Results
The results of field observations showed that two species of the tussock moth caused crop damage to oil palm plantations in the Manuhing sub-district of Gunung Mas Regency, Central Kalimantan, presented in Figure 1.Based on the results of measuring the intensity of the tussock moth attacks by calculating the percentage of oil palm plants that were attacked, with symptoms of damage to the leaves, can be seen in Figure 2. Plants in the healthy category were 4.35%.The percentage of leaf damage caused by the tussock moth attacks categories in the mild, moderate, severe and very severe types were 43.48%, 15.57%, 21.74% and 10.87%.  the tussock moth, this was confirmed to be Dasychira inclusa.The larva has two long black crests on the back of the head and grey lateral hairs along the body.This caterpillar grows to a length of 40 -50 mm.Females are more significant than the males.At night, they eat leaves from young shoots.If disturbed, they will expose urticarial hairs, which feel itchy if they touch the skin [25].These caterpillars hide in gaps in trees or bushes throughout the day, usually in groups.Based on observations in the field, the visible symptoms were holes in the leaves.This was how the caterpillars attack the inside of the leaves first.As a result of this insect attack, some or all of the leaves are damaged because they were eaten.Visually, the leaves appear to have holes or bite marks in the middle and edges of the leaves.If the damage is severe, the plant will lose its leaves.
The second type of tussock moth was identified as Calliteara horsfieldii (Saunders, 1851), the tussock moth species based on its morphological characteristics.The larvae have four pairs of long, pale yellow feathers on their backs and can reach 50 mm long.Larvae are generally located on the 25th midrib [26].Young caterpillars usually cluster around the egg-laying site and scrape the leaves starting from the oil palm leaf's lower surface, leaving the upper leaf's epidermis.Attack scars look like elongated windows on the leaves [27].Leaf damage caused by tussock moths will inhibit plant growth because photosynthesis does not occur [10]

Issues of the tussock moth and crop damage
The tussock moth attack occurred in one of the oil palm plantations in the Manuhing sub-distric of Gunung Mas Regency, Central Kalimantan, in September 2022.The tussock moth attack happened in the 2008 planting year area with an attack intensity of 17.24% (5 ha) Furthermore, after carrying out Special Detection at the location of the trees attacked by the tussock moth, the total number of oil palm trees sampled in the survey area was 46.The tussock moth attack occurred in one of the oil palm plantations in the Manuhing sub-distric of Gunung Mas Regency, Central Kalimantan, in September 2022.The tussock moth attack happened in the 2008 planting year area with an attack intensity of 17.24% (5 ha) Furthermore, after carrying out Special Detection at the location of the trees attacked by the tussock moth, the total number of oil palm trees sampled in the survey area was 46.The results of observations on all samples of oil palm plants showed that as many as forty-four plants (91.30%) experienced leaf damage due to tussock moth attacks.The detailed criteria were as follows: mild category to twenty plants (43.48%), medium to nine plants (19.57%), severe to ten plants (21.74%), and five plants (10.87%) with very severe category.While 2 (4.35%) trees were declared healthy.Most of the trees found to be attacked by the tussock moth are in specific rows, which indicate clean weeding treatment.The area affected by tussock moth attacks was in the 25 th row 25 to 45 th row.The tussock moth explosion was understandable because the location has lost vegetation cover and flowering plants.Azhar et al. [28], states that the amount of lower vegetation was positively correlated with the diversity of insect parasitoid.Flowering plants that grow around cultivated plants constitute landscape biodiversity.Flowering plants have the potential to be a source of food and shelter for insect parasitoid and predatory as natural enemies of insect pests [29].Many factors can influence interactions between pests, natural enemies, and plants, along with affecting the ability of natural enemies to suppress insect pest populations below economic thresholds.These factors include the type and number of natural enemies, the kind of flowering plant, the time of flowering plant bloom, intraguild predation, and the level of abundance of insect pests [30].The threshold level of the tussock moth is at ten larvae per frond.The explosion in the tussock moth population in this location was due to inaccuracy in implementing and reporting the results of pests monitoring.The absence of census officers during routine pest monitoring was usually by the rotation, namely once a month.Census officers only entered the location in the 3rd month or missed two wheels, so information on the existence of the tussock moth attack was not known early.
On the other hand, the ability of census officers to identify tussock moths in the larval stage was one of the main factors causing inaccurate data and information.In the initial attack phase, the symptoms of a tussock moth attack are often identified as nettle caterpillar attacks because the symptoms are very similar in the form of damage to the lower epidermis of the leaves.Apart from that, the small size of the early stages and missed observation rotations cause difficulties and missed information on the presence of early larval stages.Controlling pests using synthetic chemical insecticides, including controlling tussock moths IOP Publishing doi:10.1088/1755-1315/1346/1/0120146 using Deltamethrin 25 EC.Improving biological control mechanisms for problems in the field by conserving beneficial insects and planting flowering plants.On the other hand, the explosion of the tussock moth incident also shows the phenomenon of pest shifts at the location of the attack; nettle caterpillars dominated the previous pests.The population explosion of the tussock moth Pseudoresia desmierdechenoni, also at the location of the S. asigna attack [10]

Management strategies.
The strategy for managing tussock moth populations in the field consists of efforts to prevent and control the insect pest population.One of the keys to preventing a population explosion is the implementation of accurate and consistent monitoring or census activities [31,32].Monitoring activities begin with increasing the scientific capacity of pest census officers through routine training.We are providing knowledge to pest observers about identifying a pest, introducing the pest cycle from the larval, pupa, and imago stages of tussock moths, and introducing other types of leaf-eating caterpillars, such as bagworms and nettle caterpillars.Provide knowledge of pest-based economic thresholds at the critical population threshold.The accuracy of observing and reporting leaf-eating caterpillars that attack oil palm plants intensely influences the control strategies that will be implemented by plantation management.
Steps that can be taken to manage oil palm landscapes due to tussock moth attacks include: (1) carrying out routine pest detection activities, (2) restoring plant vegetation lost due to blanket control, (3) prioritizing biological control, which is one of the strategies in integrated pest management, and (4) installing of beneficial plant conservation in the oil palm plantation landscape as an ecosystem service.The oil palm environment has abundant ecosystem services that are beneficial in controlling pests.Several previous researchers have identified and documented beneficial insects as natural enemies of leaf-eating caterpillars [33].Regular detection activities must be carried out to prevent pest population explosions.Early detection activities are carried out on a scheduled basis, with one rotation every month.Monitoring must be carried out accurately and consistently, including census blocks and representative sample trees, and accuracy in identifying pest types, including knowledge of the biology and ecology of insect pests and activity schedules.Monitoring activities include routine, global and practical censuses.Monitoring results, such as the type and density of pests that attack, have a significant impact on the control strategy that will be implemented, such as selecting the type of insecticide if necessary and the condition of the population above the economic threshold.Monitoring for oil palm leaf-eating caterpillars or other pests should be carried out regularly every month on predetermined sample trees.Monitoring techniques can be implemented following the global and effective census method [34,35] or other methods, such as selected row samples, also implemented in several oil palm plantations.On immature plants that can still be reached by hand, a caterpillar population census should be carried out without cutting the fronds by observing the three fronds with the heaviest symptoms of attack [35].Observe pests on mature plants by removing or cutting off one of the fronds that shows the most severe symptoms of pest attack.If the population calculation results show that the number of the tussock moth larvae is more than ten larvae per frond, then control measures must be taken.
Using natural enemies of pests as biological control is the best choice in line with increasing awareness of environmental safety.Biological control uses natural enemies of pests to maintain pest population densities at a lower average than if natural enemies were absent [36].The highest abundance of insect parasitoids was in locations adjacent to flowering plants Antigonon leptopus and Turnera spp.[37].Implement biological control if the tussock moth population is below the economic threshold by conserving predatory insects and parasitoids.Installing beneficial plants such as Turnera subulata, Turnera ulmifolia, Antigonon leptopus, Euphorbia heterophylla, and Cassia cobanensis is a strategy to attract beneficial insects.Allowing the ground cover composition to contain soft weeds, such as Asystasia intrusa or Nephrolepis biserrata, also helps the presence of beneficial insects in the landscape.The ground cover in the oil palm landscape mostly consists of ferns (Nephrolepis biserrata and Stenochlaena palustris).In general, predatory insects from the Reduviidae family and Callimerus arcufer like to live in ground-cover fern species [38].The beneficial plant C. cobanensis contributes to increasing the biodiversity of insect parasitoids in oil palm plantation landscapes because the intensity of sunlight is much less.In addition, biological control can be carried out by applying proven entomopathogens, such as Bacillus thuringiensis, effective against many leaf-eating caterpillars of oil palm species [39,40,41,42,43,44].Bacillus thuringiensis is a sustainable biological insecticide, generally not harmful to freshwater fish [45], humans, pet and insectivore [46].On the other hand, in conditions where there is an explosion in the tussock moth population, control using synthetic insecticides can be considered to reduce the caterpillar population quickly.Control of larvae populations in the tussock moth explosion areas uses the insecticide Deltamethrin 25 EC at the dose of 250 ml/ha.The larval death rate reached more than 90% seven days after spraying, but non-target beneficial insects were also killed.Other active ingredients that can be applied to control fire caterpillars, including tussock moths, include cypermethrin, lambda-cyhalothrin, acephate, diazinon [33] to green labelled insecticides with the active ingredients chlorantraniliprole or flubendiamide [47,48,49].Recommends using insecticides such as a green label with a slightly toxic level of toxicity, especially if applying fogging control, because they are relatively safer for insects.
To increase the role of ecosystem services, site managers need to install the bark of the Cratoxylum spp.(Hypericaceae) in wooden boxes with a height of 1 m in each hectare of oil palm plantations (Figure 3).The bark of Cratoxylum spp.will attract the predatory insect Sycanus dichotomus and other Reduviidae families, which function as natural enemies of oil palm leaf-eating caterpillars.The most potential predatory insects as natural enemies of oil palm leaf-eating caterpillars are Platynopus melacanthus and Cantheconidea furcellata (Hemiptera: Pentatomidae) and Sycanus dichotomus (Hemiptera: Reduviidae) [50,51].Furthermore, Hendarjanti [52] stated that planting and using the bark of plants from the Cratoxylum family can attract the presence of predatory insects from the Reduviidae family; conservation of this plant is an alternative approach to biological control and providing ecosystem services.Beneficial insects such as parasitoids on C. cobanensis belong to the Chalchididae family (Brachymeria lugubris and Brachymeria carinata) and the Braconidae family (Dolichogenidea metesae and Apanteles aluella).Predatory insects from Reduviidae and Cosmolestes pictceps are ecosystem service agents important in regulating the oil palm leaf-eating caterpillars below the critical population threshold.[44].Insect conservation is essential to better integrate with overall biodiversity preservation and climate change decrease.Furthermore, insect diversity that is able to survive in the future has broad benefits, including providing sustainable ecosystem services [53].

Conclusion
The explosion in the population of minor pests of oil palm leaf-eating caterpillars occurred due to a shift in the dominance of the main pests caused by several factors, such as the influence of the host plant, climate and pest population density.The tussock moth explosion incident on oil palm plants by Dasychira inclusa (Walker, 1856) and Calliteara horsfieldii (Saunders, 1851) occurred because: 1) Pest monitoring was not carried out routinely, so pest incidents were not detected, 2) Lack of knowledge of insect pests monitoring officers, which results in inaccurate monitoring results.Carrying out regular pest detection and accurate result information is the key to preventing pest outbreaks.Observation results will determine appropriate and effective control strategies.Conservation of natural enemies by planting flowering plants and placing bark on Cratoxylum spp. as an attraction for beneficial insects is one of the preventive efforts in providing ecosystem services.Control using synthetic insecticides can be considered when there is an explosion in the pest population above the critical threshold.It is recommended to use insecticides with a green label.Ecosystem services are available in oil palm plantation landscapes that can be useful for controlling insect pests and will support the sustainable management of oil palm leaf-eating caterpillars.

Figure 3 .
Figure 3. Improving ecosystem services will ensure better management of oil palm leaf-eating caterpillars: (a) Installation of a Cratoxylum spp.bark attractant box: 1 box/ha, (b) Visitation of insects predatory from the Reduviidae family in the attractant box, and (c) Insect predatory Sycanus dichotomus preying on the tussock moth Dasychira inclusa4.Discussion4.1.Species of the tussock moths found and symptoms of their attacksThe tussock moth species that attack oil palm plantations in the Manuhing sub-distric of Gunung Mas Regency, Central Kalimantan were identified as Dasychira inclusa Walker (Lepidoptera: Erebidae) and Calliteara horsfieldii Saunders (Lepidoptera: Erebidae).Based on the morphological characteristics of

Table 1 .
Leaf damage intensity scale