Efficacy of Chromafenozide Insecticide to Control Tirathaba rufivena and Its Impacts on Oil Palm Pollinator E. kamerunicus

Newly marketed insecticide known with active ingredient Chromafenozide claimed to be potent against various lepidopterous insects, but at the same time almost non-toxic to non-lepidopterous species, including pollinators, predators and parasitoids. This trial aim to evaluate the effectiveness of Chromafenozide insecticides to control population of Tirathaba rufivena in oil palm planted on peat soil and its impact on pollinator weevil, Elaedobius kamerunicus. The trial was divided into two parts which are field assessment of insecticides efficacy and laboratory assay to know the direct effect of insecticide application on E. kamerunicus. Besides Chromafenozide, insecticides used in this trial Cypermethrin and Bacillus thuringiensis var kurstaky as comparison. The results of efficacy test showed that Tirathaba infestation decreased significantly in the Cypermethrin, B. thuringiensis, and Chromafenozide treatments compared to control. However, among these treatments did not show a significant difference. Nevertheless, each of the tested insecticide caused significantly mortality to E. kamerunicus. E. kamerunicus mortality rate of each insecticide treatment showed that Chromafenozide was less detrimental as compared Cypermethrin, but significantly detrimental to B. thuringiensis. B. thuringiensis was not significantly different compared to control.


Introduction
In Indonesia, Tirathaba rufivena (Bunch moth) is one of common oil palm pest and can become pandemic, especially in young oil palm.T. rufivena moths laid eggs in the bunches, particularly those that are overripe or decaying bunchs, and in inflorescences.Hatched larvae feed on the surface of maturing fruit or bore into developing fruit.They can occasionally be seen tunelling into the base of a spear leaf.Larvae morphology are light to dark brown sized up to 4 cm, and pupate inside the bunch (Corley & Tinker, 2003) [1].The duration of a complete metamorphosis cycle of T. rufivena was about 51.63 ± 3.80 days.The most detrimental stage of the pest to oil palm is at larval stage, which took 33.90 ± 2.60 days before pupating (Ming, et.al., 2020) [2].
Tirathaba infestation are reported to negatively impacted palms especially those planted on peat age between 5-7 years old.The hot and humid condition of peat soils encouraged the spread of the Tirathaba bunch moth when the palms approach maturity.In severe infestations, it can cause > 50 % crop losses (Ming, 2020; Lim, 2012) [2] [3].The infestation is identified by the presence of long tubes of silk and frass which is built by the pest.The larvae stage of pest does most of the damage by feeding or scraping leaving holes on immature fruitlets.Larvae of early instar stage often attack on 1308 (2024) 012044 IOP Publishing doi:10.1088/1755-1315/1308/1/012044 2 male inflorescences while larvae of older instar stage attack on female inflorescences and bunch (Yaakop et al., 2012) [4].Young bunch was preferred by T. rufivena because this bunch had soft exocarp and mesocarp (Ming et al., 2016) [5].During this period, the fruitlets were susceptible to infestation of T. rufivena larvae.T. rufivena heavy infestation during young bunch stage can lead to the abortive process of the bunch.The abortion of young bunch eventually reduced the FFB quantity (Idrus et.al., 2018) [6].
However, the effectiveness of Chromafenozide for controlling lepidopterous pests, especially oil palm bunch moth, was not been reported yet.Therefore, the study was carried out to determine the effectiveness of Chromafenozide against T. rufivena and its impact to insect pollinator E. kameruicus.

Materials and methods
The trial was carried out from March to June 2021 on peat area with oil palm year of planting 2018 in PT Bhumireksa Nusasejati.The trial was laid out in randomized complete block design (RCBD) with 4 treatments.Each treatment was replicated 3 times with 10 measured palms.The treatments are shown below: Pre-treatment assessment was implemented for three days before treatment for all, 120 measured palms.
Each measured palm was confirmed to be infested by Tirathaba with visual symptom such as fresh frass on the surface of the bunch, then categorized according to its severity index (Table 2. Severity Index of Fruits Bunch Damaged).For each assessment within each replicate, the number of bunches with and without larval damage was recorded.

Treatment Application
The insecticides used (Chromafenozide, Cypermethrin and B. thuringiensis) were sprayed onto inflorescences and bunches of selected palms due to those are the living site of the larvae.The insecticides were applied using a knapsack sprayer with a long lance to direct the solution spray onto the top and back of the infested bunches.Prior to application, calibration has been conducted to ensure uniform and accurate rate of treatments.Spraying was carried out top down, prioritized first on inflorescences then developing bunches to ripening bunches in the treated palms.Infested bunches must be sprayed thoroughly until wet estimated 1-1,5 L each palm.The application was carried out in the morning on sunny days.Treatments were conducted for two rounds application with 30 days interval.

Observation Parameters
The bunches with fresh frass coverage indicated the severity of T. rufivena infestation.All bunches (developing to ripening bunches) in each measured palm were observed visually at 3, 7, 14, and 30 Days After Treatment (DAT) for the 1 st round then 14 and 30 DAT for the 2 nd round.Bunch moth infestation data recorded then classify into 5 categories with scoring criteria below: The severity of Tirathaba damage then calculated using formula:

Laboratory Assay on Direct Effect of Insecticide Application on Elaedobius kamerunicus
This laboratory assay was conducted to find out effect of tested insecticide to E. kamerunicus population, e.g mortality rate.Laboratory assay procedures were as described by Prasetyo & Susanto (2019) [10].E. kamerunicus weevils were obtained from male inflorescences collected from the field.Various insecticide test as field assessment and plastic incubator jar (d=20 cm; h=22 cm) cover with muslin cloth were prepared.Each incubator jar contains one male inflorescence spikelet and 10 weevils consisted of 5 male & 5 females.Each insecticide dissolved with water as field assessment rate, then sprayed onto incubator at 10 ml/jar.Each treatment consisted of 10 incubators with 3 times replicates.The number of live and dead weevils were counted and recorded every day for 4 days consecutively.The percentages of weevil's mortality were calculated.On the last day of observation (day 4), the various efficacy values were calculated based on the Abbott formula (1925) as follow [11]: Corrected Mortality (%) = (X-Y)/X x 100 X = ∑number of weevil alive in control Y = ∑number of weevil alive in treatment

Statistical Data Analysis
The collected data were analyzed using Analysis of Variance (ANOVA) followed by Tukey test with 95% confidence level if there are significant different among treatment.

Field Assessment of Insecticides Efficacy
Tirathaba infestation at PT Bhumireksa Nusasejati was reported sporadically in several field and the infestiation was confirmed via census.The condition of Tirathaba infestation was indicated by the presence of frass and was significantly different from the unaffected fruit (figure 1).Tirathaba larvae frequently found behind the fresh frass (figure 2).As shown in table 3 the infestation rate per palm ranged from 45.3% up to 56.9%.Visual assessment on the percentage of frass coverage on the fruit bunches was used to determine the severity category.Then it could estimate the larvae present in bunch observed (Ming et.al, 2020) [5].In line with that, Idrus (2017) [12] state that young bunch with new frass and high infestation have the highest count of larvae.Location with high rotten bunches are having high Tirathaba infestation and larvae count.Besides, location with high rotten bunches also had low male inflorescence.During pre-treatment assessment period (three days prior to treatment commencement), the percentage of bunch moth infestation severity varied from 20,5% (light) to 27,7% (moderate).After the insecticide application, the percentage continuously decrease significantly for all treatment as compared to control (figure 2).Tirathaba bunch moth infestation severity on control was also declining attributed to the life cycle.However, decreased was not as steep as the plot sprayed with insecticides.a b

Figure 2. Effects of several insecticides active ingredient on the infestation severity of the bunch moth T. ruvifena
After three days after treatment, infestation severity of bunch moth decreased from moderate to light in all treatments.Cypermethrin (from 27,1% to 13,7%), then B. thuringiensis (from 21,6% to 11,5%), followed by Chromafenozide (from 20,5% to 11,7%) and control (from 25,6% to 20,7%) (Table 3.).Although the infestation rate was reduced, the tested insecticides did not show a significant effect compared to the control during the first week after 7 DAT, the effect of the tested insecticide application showed a significant difference compared to the control.Cypermethrin to 5,9%, Chromafenozide and Bacillus thuringiensis the infestation were at 6%, 8.2%, and 5.7% respectively.Further decreased reduction was recorded from 14 DAT for all insecticides  ).The value of severity percentage in all treatment including control are under 30% because the ratio between healthy bunches are higher than damaged bunch with various category from light to very severe.Based on this, Tirathaba infestation in trial site was categorized to light to moderate category.Larvae population in the trial site varied from 2 -10 larvae.Table 5. showed that percentage of continuous reduction of severity rate has significantly different (p=<0,01) at 7 DAT between Cypermethrin (77,7%) and untreated (13,4%) while B. thuringiensis (54,2%) and Chromafenozide (54,4%) are similar.Therefore, Chromafenozide and B. thuringiensis has slower effect compared to Cypermethrin.Numerically, B. thuringiensis showed the highest percentage on reducing the Tirathaba infestation severity at 14 and 30 DAT (first round) followed by Chromafenozide and Cypermethrin.After 30 DAT for second round, the result among treatments were not significantly different except for control.The highest reduction of severity rate was observed in B. thuringiensis treatment.
All the insecticides used have a different mode of action.Cypermethrin as a synthetic pyrethroid insecticide, it's mode of action is non-systemic and has knock-down effect.It only remains on the targeted site of the plant and must be in contact and absorbed by the insect.Cypermethrin also works as a stomach poison when consumed.Basically, Cypermethrin attacks the nervous system of the insects that can affecting the neuron function (Najwa et. al., 2020).Different from Cypermethrin, Chromafenozide is an insect growth regulator, act as ecdysone agonists at all stage of the insect's metamorphosis.It may disturb the molting process and interrupt the feeding behaviour of the larvae (Yanagi, 2009) [13].Meanwhile, B. thuringiensis is a well-known bioinsecticide with its endotoxin, an insecticidal crystal protein which are lethal when eaten by a susceptible insect.It's application for 2 rounds with 30 days interval could reduce the Tirathaba infestation severity up to 99,16%.Generally, all insecticide application significantly reduced the severity index compared to control.In 3 DAT, there were not significant different affect all insecticide compared to control.But at 7 DAT, Cypermethrin showed significantly reduce the severity highly.

Figure 1 .
Figure 1.Tirathaba-Infested bunch (a) and Tirathaba larvae (b) a 20,70 a 21,91 a 15,17 a 18,27 a 15,20 a 4,22 a Number in the same column followed by the same letter are not significantly different at P=0.05 based on Tukey Test T. ruvifena infestation severity categorized by the percentage of larval frass covered on the bunch surface.Ming et al, (2020), categorize larva population as follows: the mean number of larvae found in oil palm fruit bunches were 22 larvae in the severe category (frass coverage >50%), 10 larvae in moderate category (frass coverage between 25 -50 %), and 2 larvae in light category (frass coverage

Figure 3 .
Figure 3. Tirathaba infestation at 30 days after treatment of several insecticides

Table 1 .
Rates of insecticides for Tirathaba control trial.

Table 3 .
Severity (%) of oil palm fruit bunch damaged after application of several insecticides

Table 6
shows the mortality of E. kamerunicus after application of Cypermethrin, B. thuringiensis, and Chromafenozide.It shows all insecticides were significantly harmful for pollinator weevil E. kamerunicus.The use of Cypermethrin and Chromafenozide significantly caused higher mortality of E. kamerunicus as compared to B. thuringiensis.Direct application of insecticide against E. kamerunicus resulted that Chromafenozide was significantly safer than Cypermethrin, but significantly worse than B. thuringiensis.B. thuringiensis impact was not significantly different compared to control for mortality rate of oil palm pollinator E. kamerunicus

Table 5 .
(Ahmad et al., 2009;2012;eevil E. kamerunicus after insecticides applicationNumber in the same column followed by the same letter are not significantly different at P=0.05 based on Tukey Test.Application of Cypermethrin 5% at 2 ml/L showed maximum mortality rate at 100% mortality on a very first day after application corresponding toAhmad et al., (2009;2012)[14]; Yusdayati and Hamid (2015).Meanwhile, B. thuringiensis biopesticides based application are not toxic to the E. kamerunicus and also beneficial insects as compared to Cypermethrin(Ahmad et al., 2009;2012; Prasetyo et al.,  2015).Whereas, at 1 DAT Chromafenozide causing mortality rate 16.7% higher than B. thuringiensis at 1.3%.It increased at 4 DAT up to 100% for Cypermethrin, 38% for Chromafenozide, 15.7% for B. thuringiensis, and 11.5% for control.Analysis with corrected mortality rate resulted that B. thuringiensis application caused pollinator weevil's mortality at 8,8%, whereas Chromafenozide reach 49% while Cypermethrin at 100%.Therefore, B. thuringiensis is more friendly to E. kamerunicus as to application of agrochemical.