Plant extract as kairomone attractant to cocoa pod borer, Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae) in cocoa farm

In Southeast Asian countries, the cocoa pod borer (Conopomorpha cramerella) is a significant pest that can cause damage to cocoa production. A potential method for controlling this pest is to use kairomone attractants made from plant extracts. This study aimed to determine the attractiveness of Carrot Leaf Extract (ElCar) and Coffee Leaf Extract (ElCoff) to C. cramerella. Approximately one hectare of cocoa plants was used in the experiment, and observations were made with a three-day interval for two months. The findings demonstrated that the use of plant extracts as kairomone attractants was effective for attracting adult females. No adult male populations were captured during the period of observation. 116 female adults were captured in ElCar, 25 at 5% concentration, 27 at 10% concentration, and 64 at 15% concentration. 100 adult females were captured in ElCoff: 16 at 5% concentration, 51 at 10% concentration, and 33 at 15% concentration. Carrot extract at a concentration of 15% contained the highest percentage of attractant, putting it in the very high attractant category (86%). The percentage of high attractant in coffee extract was found to be 10%, which was in the very high category (80%).


Introduction
The presence of volatile compounds (semiochemicals) like pheromones and kairomones in nature causes chemodiversity, which affects how insects and plants communicate with each other [1].How plants interact with insects depends on the complexity of olfaction and the volatile compounds available in the environment.The olfactory apparatus is how insects use chemical compounds to find host plants, enemies, and places to lay eggs [2].In the integrate pest management (IPM) system, semiochemicals can be used to cut down on the use of synthetic insecticides [3].The most widely used semiochemicals in managing insect pests are pheromones and kairomones, both of which can be used for monitoring to keep insect pest populations below the threshold [4].
Insects need to be able to find their host plants, especially when they want to lay eggs.Chemical compounds in the plant help insects do this [5].The use of pheromone and kairomone attractants is considered an effort to reduce cocoa pod borer (CPB) populations [6].Attractant compounds have been used for a long time to control and monitor insect pests.The most frequently used compounds are pheromone and kairomone compounds from plants, which are widely used in the field to attract CPB male adults and reduce CPB populations [7].In addition to the use of pheromones, kairomone compounds produced by plants can be an alternative way to obtain attractant compounds for insect pests.Kairomones of plant origin can stimulate oviposition not only in insect pests but also attract natural enemies [8].
Many male CPB insects can be caught by the kairomone compound that is made from lychee fruit extract.This shows that CPB insects are not only attracted to pheromone compounds [9].Several types of plants have the potential to act as natural controls, and some of them can act as attractants for insects.The advantage of using attracting compounds for insect pests is that they can reduce the level of attack without leaving residues in nature.Laboratory test results showed that carrot leaf extract (ELCar) and coffee leaf extract (ELCoff) were attractive to CPB adult insects [10].Based on these laboratory tests, it is necessary to carry out field tests to evaluate ELCoff and ELCar as agents for CPB in the field.

Leaves sample from the field
The plant samples used for extraction were Robusta coffee leaves and carrot leaves.The Robusta coffee leaves were selected based on their dark green color and age and were located in the middle of the outer canopy.These leaves were sourced from Pinrang district in South Sulawesi.The carrot leaves used were freshly harvested and sourced from Kanreapia Malino Village in Gowa Regency, also located in South Sulawesi.

Plant extraction
The plant samples used in this study were old leaves of coffee and carrot.All the plant materials obtained was thoroughly washed after that cut into small pieces and air-dried for 2-3 days.The extraction process involved weighing the leaves and macerating them with 70% methanol solvent at a ratio of 4:1 (solvent: plant) for 7 days, on this method the dry leaves is not powdered.After 7 days, the ELCar was filtered and poured into a closed container.The ELCar and ELCoff liquid contained 70% methanol and needed to be evaporated using a rotary evaporator (RV-10) at a speed of 120 pm at a temperature of 50-55 °C.To obtain the crude extract, solvent evaporation was carried out using a water bath at a temperature of 60°C.After obtaining the ELCar and ELCoff extracts, the extracts were prepared in 3 concentrations for the treatment, namely 5%, 10%, and 15% for each extract (ELCar and ELCoff).

Trap model
The traps used in this study were white delta traps.Delta traps are the most widely used traps for trapping CPB adult insects due to their effectiveness in the field and ease of maintenance.Additionally, delta traps can be used multiple times [11].The delta trap is made of white impraboard which is waterresistant and protects the extract from direct sunlight.It is triangular in shape and has a laminated paper receptacle inside that has been coated with glue.

Field experiment
The research was done on a uniform cocoa farm with 12 meters between each trap.A line transect method was used to place the traps.The traps were hung in the cocoa canopy at a height of 1.7-2 meters from the ground.Observations of trapped adult CPBs (males and females) were conducted every 3 days for 10 weeks.The percentage of attraction data obtained was analyzed using the attractant formula proposed by Sighamony et al. (1984) [6].All data analyse by non-factorial randomized block design.

Result and discussion
The number of adult CPB insects caught in all of the treatment extracts was much higher than in the control, which shows that ELCar and ELCoff were attractive to CPB.During the 48-day observation period, 116 adult CPB insects were caught on ELCar, 100 on ELCoff, and only 16 on the control (Figure 1).From statistical analysis control and ELCar and ELCoff treatments is significant different while both ELCar and ELCoff is not significantly different for caught adult CPB.These results demonstrate that applying ELCar and ELCoff with certain concentrations on cocoa plantations can effectively attract CPB pests within a 48-day period.ELCar at a concentration of 15% attracted more CPB adult insects than ELCoff at the same concentration, whereas at a concentration of ELCoff of 10%, CPB adult insects were more attracted than ELCar at the same concentration (Figure 2).Statistically the result of ELCar 15% and ELCoff 10% shows not significant different but if compare to concentration ELCar and ELCoff 5% is significant different.These results indicate that the attractiveness of CPB adult insects to coffee and carrot extracts varies depending on the concentration level.Specifically, the concentration level of 15% for ELCar and 10% for ELCoff were found to be more attractive to the CPB adult insects.The attraction of adult CPB insects to ELCar and ELCoff extracts was due to the presence of chemical compounds in the form of attractive secondary metabolites.Chemical properties are important in the olfaction of insects, which will affect the interaction of plants and insects [12].Carrot and coffee leaf extracts contain phenolic compounds with a single aromatic ring known as phenolic acids.The main phenolic compound is chlorogenic acid [13].Carrot is rich in a phenolic compound known as Chlorogenic Acid (CGA), the esters of caffeic and quinic acids, which are biologically important phenolic compounds present in many plant species [14].Chlorogenic acid is found in several other plants, such as blueberries, grapes, pears, apples, sweet potatoes, cherries [15], and cocoa [16].
Chlorogenic acids are also present in cocoa pods that are 2-3 months old [17].That is why CPB insects lay their eggs on cocoa pods when they have a size of 7-9 cm, which is 2-3 months old [18].The differences in CPB responses at various concentrations of ELCar and ELCoff show that even though the two plants contain the same kairomone or chlorogenic acid compounds, the response of CPB pests to the two extracts is different depending on the concentration.The proportion of chemical compounds in a plant can affect the interaction of plants and insects [12].Figure 2 shows that the 15% concentration of carrot extract attracted more CPB pests than the 5% and 10% concentrations, while the coffee extract attracted the most CPB pests at a 10% concentration compared to the 5% and 15% concentrations.This shows that ELCoff and ELCar have different levels of interest at each concentration.Carrots contain more chlorogenic acids than coffee leaf extract [10].Chlorogenic acid found in cocoa pods acts as a stimulant for eggs [16].From the results of the identification of CPB adults trapped in each extract, it showed that 100% of the trapped CPB adults were female, which can be seen from the abdomen with the characteristics of having an ovipositor showing anal papillae, as shown in Figure 3.These results indicate that ELCar and ELCoff can be alternatives to pheromones as attractants for CPB female insects.With many adult female CPB insects attracted to these two extracts, there is enormous potential for developing formulas for use as kairomone attractants.Attracting adult female insects can help reduce the population of the next generation, and thus, it is hoped that damage to the cocoa pods in the field will be reduced.

Conclusion
The plant extracts from carrot (ELCar) and coffee (ELCoff) successfully attracted the CPB imago.ELCar attracted the most with 116 CPB imago, while ELCoff attracted 100 CPB imago.The effective concentration for attracting CPB was 15% for ELCar and 10% for ELCoff, which corresponds to the levels of very high attraction for CPB in ELCar 15% and ELCoff 10%.All the CPB trapped in this trial were female.

Acknowledgment
I am grateful to all the team members who worked to launch and make this research successful so that it can be completed.

Figure 1 .
Figure 1.Total number of CPB imago captured in ELCar, ELCoff and control in 48 days observation.

4 Figure 2 .
Figure 2. Total population CPB captured at each concentration during the observation.

Figure 3 .
Figure 3. Abdomen identification of CPB found in the trap showing ovipositor (A) and showing anal papillae (B).Based on the attraction percentage formula developed by Sighony et al. (1984), ELCar at 15% and ELCoff at 10% are classified as very high attraction (class 5), while ELCoff at 15%, ELCar at 10%, and ELCar at 5% are classified as high attraction (class 4).ELCoff at 5%, falls into the medium attraction category (class 2).

Table 1 .
Percentage of attraction of ELCoff and ELCar at each concentration.