Investigation of termite attack, Macrotermes gilvus Hagen (Termitidae: Blattodea), to cocoa (Theobroma cacao)

Macrotermes gilvus is a major pest in the cocoa cultivation industry in Indonesia, with huge productivity. The success of a termite control technology is largely determined by the availability of information about the biology of termites which are pests. Investigating M. gilvus attacks was surveyed on polyculture cocoa plantations in Pidie, Aceh Tamiang, and Southeast Aceh Districts, Aceh Province. We found various levels of termite attacks characterized by mounds (nests) and galleries on the cocoa. The presence of nests and galleries damages the pith tissue and creates empty spaces, which are later filled with soil. Lack of land sanitation can trigger termite attacks on the plantations.


Introduction
Cocoa is one of the leading crop commodities that plays an essential role as a source of foreign exchange in Indonesia [1].This plant is very suitable for planted by the community, because it can flower and bear fruit throughout the year.Also, cocoa beans can be processed into chocolate raw materials providing high economic value [2].However, the potential of cocoa yield loss caused by termite as one of major insect pest becomes a highly-concerning issue [3].Among 3.105 species of termites, approximately 185 species have been identified as pests worldwide.[4].Termite attacks caused 50.66% of cocoa damage, from seed to adult [5].Termite attacks can disrupt plant metabolic processes by injuring tissue in roots and trunks.According to Djuideu et al., [6] indications of termite attacks on cocoa are characterized by the galleries in outside or inside bark, the soil around the tree, and the roots.In Africa, more than 90% of damage in agriculture is caused by termites of genus Macrotermes [7], which can reduce cocoa productivity [8].One termite species as a potential pest for cocoa plantations is Macrotermes gilvus.which has a wide distribution in Indonesia [9,10].Information regarding termites as pests for cocoa plants has been reported by Ollo et al. [11], Akpsee et al. [5], Djuideu et al. [6], as well as only information on the ecology of the termite Macrotemer gilvus has been reported [9,10,12].However, a special study regarding the existence of Macrotemer gilvus as a pest of cocoa plants in Indonesia has never been carried out.Therefore, the aim of this research is to investigate the presence and conditions of attack by this species on cocoa plantations, as a basic guideline for effective c to be implemented.

Study Site and Termite Collection
From 2021 to 2022, we surveyed termites on polyculture cocoa plantations in Pidie, Aceh Tamiang, and northeast Aceh (Aceh Province, Indonesia).Survey was conducted in 0,5 ha of cocoa plant for 10 study site.Biological and ecological data were recorded, and termites were preserved in 80% ethanol before transporting them to the laboratrium for identification.The identification for species level termites was undertaken in the Biosystematics Laboratory, Syiah Kuala University, Indonesia.

Sample Identification
Termites were identified using morphospecies characters of head, mandibles, thorax, and antennae for soldier and worker castes based on the references to [13][14][15] and termite specimen collection at Biosystematics Laboratory of Universitas Syiah Kuala.

Description and distribution of the termite Macrotermes gilvus
A total of 7 colonies were identified as attacks on cocoa by this species.This genus, Macrotermes, is famous for its large head size and dimorphism in the soldier caste, which is the existence of dimorphism soldier caste into major and minor soldiers.Major soldier termites, the capsule size reaches 4.2 mm, while in minor soldiers, it is 3.0 mm [16].
Major soldier: Head capsule dark reddish-brown; mandible black; thorax duller brown than the head, and tergite duller than thorax.The antennae and legs pale to yellowish brown.Postmentum reddish brown, like the color of the head capsule.Head subrectangular in shape, with the anterior part shorter than the posterior; a labrum at the anterior end dome-shaped and equipped with a small hyaline tip; small fontanel in the center of the head capsule.Mandibles slightly curved at the ends, thick, and shaped like a strong sword; inside of the left mandible crenulation at the bottom.Antenna 17 segments with uniform sizes.The potmentum five times as wide as it long, with a hexagonal anterior part that narrows in the middle and widens again at the bottom.The pronotum looks striking of a saddle shape (Figure 2).Minor Soldier: Head capsule reddish brown, with the anterior part containing the labrum slightly thicker.The mandibles blackish-dark brown.The color of the antennae, thorax, and tergite yellowish brown, paler than the color of the head.Postmentum is brown.Head shape subrectangular with a more rounded base, while the major soldier's head more faceted; fontanels absent, and hyaline faint; a coneshaped labrum present.Mandibles are long, thin, and curved at the ends.No marginals found on both sides of the mandible.Antenna 17 segments.The postmentum is twice as long as it is wide and not too narrow in the middle; the anterior part is hexagonal and does not widen at the bottom.Pronotum saddleshaped but more inconspicuous (Figure 2).M. gilvus is distributed in Indonesia (Figure 3.), especially in Sumatra Aceh, Java, Kalimantan, Sulawesi, and Maluku [13,[17][18][19][20][21].This termite has a wide distribution in Southeast Asia from 0-1000 meters above sea level, particularly in lowlands, urban areas, and plantations [13].).According to Aiki et al. [22], fungi gardens are the colony's primary food source.These components also function as thermoregulators in termite nests: fungi absorb excess moisture released when air humidity decreases and emit heat during growth.Abundant galleries on cocoa indicated high colony activity, and they use galleries for transporting food sources to the nests [24].We also found that the galleries are helpful for the termites to distribute their member to the neighboring cocoa plants.Besides that, the wooden supports farmers use to keep the cocoa trees sturdy have also become a medium for termite distribution from the ground to reach the upper parts of the plants (Figure 3).Hence, it is recommended that the choice of supporting wood must have high resistance to termite attacks, and the supporting wood is placed not directly adjacent to the ground but is given a base first to protect direct contact from the ground.
In several cases, we found that M. gilvus also collected from rotting tree trunks or logs.This species attacks the stem's pith and creates an empty space that will later be filled with soil.The outer bark of the tree trunk remains intact.The soldier caste is very agile and aggressive when the colony or part of the colony is disturbed by predators.Habitat on cocoa plantations is optimal for M. gilvus, this is related to the greater availability of organic material [12].
Planting cocoa in a polyculture system could trigger termites to attack cocoa by providing additional food sources and a medium for M. gilvus to construct galleries from infected cocoa to the surrounding plants and cocoa.This close planting distance results in the connection of galleries between one cocoa plant and another, both from nearby tree branches and galleries connected to the ground surface.The intensity of termite attacks is also influenced by its sanitation [24].Land maintenance, which includes pruning, sanitation, and pest control strategies.Intensive maintenance can reduce the amount of litter and bushes on the ground and provide cellulose for the termites.The effective use of termiticide for M. gilvus could be the last alternative if several biological control strategies were ineffective.Termite control strategies need more investigation research because termites have unique life strategies that construct secretive nests and galleries, making them difficult to detect.Eradicating deep nests and burrows in the summer before the rainy season to prevent new colony growth in the rainy season [25].Therefore, regular monitoring the plantations is critical to reduce termite attacks on the cocoa.

Conclusions
Macrotermes gilvus has been identified as a pest for the cocoa plantation by the existence of mounds (nests) and galleries.Detection of termite attachment at the early stage of plant is considered challenging because this insect starts to consume the wood material inside the plants.Therefore, it is necessary to have a strategy to control termites by clearing the land, using adequate wooden supports, pruning, removing unnecessary wood material on the ground, and applying several biological control strategies instead of using termiticides.

Figure 4 .
Figure 4. (A) An indicator of M. gilvus termite attack is a mound nest containing a fungus comb.(B) tree support wood as a medium for invasion by M. gilvus termites