Using mung bean as a trap crop and biopesticide for control of soybean pest

Many pests attack soybean plants and can cause high-yield losses. To reduce crop damage, using chemicals in the field can potentially cause harmful effects on the environment. Using traps-crops, and biopesticides will be tested as an effective and safe control method. The research was done in the dry season of the tidal land of Tumih Village South of Kalimantan. The design used was RCBD which consisted of six treatments and was repeated four times. The treatment tested were 1). Check, 2). Biopesticides 6 times, 3). Biopesticide 4 times, 4). Biopesticides 6 times + mung bean as trap crop 6%, 5). Biopesticides 4 times + mung bean as trap crop 6%, 6. Insecticides 6 times. The results indicated that armyworms Spodoptera litura and Lamprosema indicata were important pests. Armyworm attacks in the vegetative phase reached 82%. However, the yields obtained were around 2,069 to 2,463 t/ha. Soybean yields in treatment plots with 6% trap crop were 1,664 to 1,969 t/ha. Anjasmoro varietal is not recommended In endemic areas of the armyworm.


Introduction
Indonesia has a tidal area of 20.1 million ha [1].This land is spread across Sumatra, Kalimantan, Sulawesi, and Papua [2]; and is suitable for developing food crops, including soybeans.Soybean cultivation has various technical constraints, including the lack of availability of quality seeds in a sustainable manner, farmers not yet developed new superior varieties, pest and disease attacks, and limited land for development.Prices and low farmers' profits also affect the increase in soybean yield [3]; [4].Santosa [5] reported that "soybeans are more sensitive to climate change which can reduce production, both in El Nino (10.7%) and La Nina conditions (11.4%)".Nugraha et al. [6] also reported that "soybean competitiveness is relatively low compared to corn; it is also vulnerable to biotic and abiotic stresses".One of the constraints to developing soybeans in tidal swamps is the damage caused by insect pests.
Pests are one of the biotic stresses in the vegetative and generative phases of soybean cultivation and cause severe yield losses.In soybean cultivation, leaf-eating caterpillars (especially Spodoptera litura armyworms), pod eaters (fruit caterpillars, Helicoverpa armigera), pod borer (Etiella zinckenella), brown ladybugs (Riptortus linearis), green ladybugs (Nezara viridula) and pale green ladybugs (Piezodorus hybneri) are the main pests that are considered harmful [7], [8].The area of attack by these pests in the 2013 planting season reached 0.1% of the soybean planted area [9].Pests damage soybean leaves and pods and cause yield reductions of up to 25% [10].According to Rustam [11], every year, pest attacks cause a 15 to 20% loss in soybean production, both directly and IOP Publishing doi:10.1088/1755-1315/1312/1/012021 2 indirectly.Norris [12] stated that "pest attacks have an impact on decreasing the quantity and quality of crop yields, such as physical damage, chemical toxins, disease vectors, increased production costs, social and environmental costs, and consumer rejection".So effective, and safe pest control needs to be tested.
Until now, efforts to control soybean pests are still focused on chemical control.Excessive and unwise use of chemical pesticides can lead to the death of predators and parasitoids.In addition, it was also reported that there had been resistance to commonly used insecticides, so pests are difficult to control with chemical insecticides [13].Therefore, research is needed on alternative controls that combine several control components, such as plant extracts (vegetable insecticides), insect pathogens, trap plants, and resistant varieties that are relatively safe for the environment.Biopesticides involving Neem and Nuclear Polyhedrosis Virus (NPV).Indiati et al. [14] stated, "Both materials effectively suppress the population and severity of armyworm attacks on soybean plants in tidal swamps".Trap crops are a habitat management strategy that aims to reduce damage to primary crops by combining them with other desirable plants to attract insect pests [15].In Indonesia, the mung beans Merak variety has been used as a trap crop in controlling pod-sucking pests in soybean plants [16].
This research aimed to evaluate soybean pest control technology by combining neem seed powder (NSP) and Spodopteralitura Nuclear Polyhedrosis Virus (SlNPV) as a biopesticide and mung bean as a pod-sucking trap crop in tidal fields in South Kalimantan.

Materials and Methods
The study was done in the dry season of the tidal land of Tumih Village South of Kalimantan.Anjasmoro variety soybean seeds, neem seed powder (NSP), Spodopteralitura Nuclear Polyhedrosis Virus (SlNPV), alkyl aryl alkoxylate adhesives, synthetic insecticides Lambda-cyhalothrin and deltamethrin, urea fertilizer, SP36, and KCl were the substances utilized in the current study.The ILETRI Source Seed Procurement Unit in Malang produced the Anjasmoro soybean and Merak mung bean seeds.The Plant Fiber Institute and Sweetener is suppliers to NSP; NSP is produced by crushing or grinding 50 g of neem seeds, which are then dissolved in 1l of water (w/v).The mixture is then filtered, 0.5 ml/l of alkyl aryl alkoxylate adhesive is added, agitated, and it was ready for use.SLNPV was prepared at the ILETRI Entomology Laboratory; alkyl aryl alkoxylate adhesives, the synthetic insecticides cypermethrin, lambda-cyhalothrin, and deltamethrin, and fertilizers formed of urea, SP36, and KCl bought from nearby agricultural stands.Six treatments and four replications formed the RCBD design.Two to three Anjasmoro soybean seeds per hole were planted in 4 m × 30 m plots, with 40 cm x 15 cm spacing.After soil cultivating, dolomite as much as 1 t/ha is spread over the soil surface.Fertilization: given at planting, 50 kg each of urea, SP36, and KCl per hectare.The treatments included 1).Check, 2).Biopesticides (mixed NSP 50 g/l + SlNPV 2 g/l) (6 times at 21, 28, 35, 42, 49, and 63) days after planting (DAP), 3).Biopesticide (mixed NSP 50 g/l + SlNPV 2 g/l) (4 times at 21, 35, 56, and 70 DAP), 4).Biopesticides 6 times + mung bean as trap crop 6%, 5).Biopesticides 4 times + mung bean as trap crop 6%, 6. Insecticides (6 times at 21, 28, 35, 42, 49, and 63DAP).Mung bean variety "Merak" as a trap crop is grown simultaneously with soybeans.Observations were made of the following: 1) insect pest population densities at 45 and 60 DAP; 2) the severity of leaf-eating caterpillar attacks at 60 and 80 DAP; 3) the severity of pod borer and pod sucker attacks at harvest; and 4) grain yields at harvest.Five plant samples, taken diagonally, were examined for the severity of leaf-eating caterpillars.The attack intensity is calculated based on the score (1-4), then entered in the formula:

Data analysis
The F test assessed the data at a 5% level.Additionally, the lowest significant difference test (LSD) with a significance level of 95% was applied to identify changes between treatments.When the soybeans were 45 days old, the pests found included armyworms: instars 1 to 5, leaf roller caterpillars, and grasshoppers.The armyworm population was 2 larvae/40 m 2 ; the leaf roller population was 3 larvae/40 m 2 , while the highest grasshopper population was 4 insects/40 m 2 .Not significantly different between treatments (Figure 1).At the age of 60 DAP, the armyworm population increased, with a population density of between 6 to 27 larvae/40 m 2 (Figure 2); the highest population was found in the chemical insecticide-6x plots, while the armyworm population was lowest in the biopesticide based on the monitoring plots.

Population density of the pest
Besides the armyworm, a pod-sucking pest, Riptortus linearis has also been found on mung bean plants grown as pod-sucking traps (6% of the soybean area).The population of pods sucker on mung bean trap plants was high, with 85 insects/30m and 76 insects/30m at the monitoring and scheduled bioinsecticide treatment (Figure 3).

Pest attack intensity
The high armyworm population has a significant effect on crop damage.In Figure 4, it can be seen that crop damage to plants aged 60 DAP ranged from 40% to 62%; the lowest damage was in the biopesticide based on the monitoring plots, while the highest was in the check plot.At 80 DAP, the armyworm intensity continued to increase in the range of 70 to 82%, significantly different between the treatments tested (Table 1).The attack intensity of armyworms between biopesticides-6x, biopesticides-4x, and insecticides-6x was not significant; this attack intensity was lower than in the other treatments.
Seed damage caused by pod sucker attacks ranged from 8% to 17% (Table 1).The lowest attack occurred in the insecticides-6x plot and was not significantly different from treatment no. 4 (Biopes-(6x) + trap crop 6%), treatment no. 5 (Biopes-(4x) + trap crop 6%), and biopesticides-6x.Planting the green bean variety Merak with an area of 6% as a pod-sucking trap plant affected the low attack of pod-sucking in plots with trap plants.While the intensity of the attack by pod-sucking pests on trap bean plants was high, the yield of dry bean seeds attacked by sucking pests reached 270 g or the equivalent of 31% of the total weight of dry bean seeds produced from a single row plot 30 m long, while the weight of dry bean seeds healthy green 590 g (Figure 5).Seeds attacked by pod borers and pod eaters were relatively low, ranging from 0.5 to 2.3% and 1 to 5.5%, respectively (Table 1), so they had little effect on soybean yield.

Plant yield
Soybean harvested at 85 days.The number of soybean plants ranged from 104 to 137 plants/4m 2 ; soybean plants harvested at insecticides based on the monitoring treatments significantly differed from other treatments.The number of filled pods/plant varied from 27 to 43 pods/plant; Treatment number four (biopes 6x + mung bean trap crop) had the fewest filled pods and scheduled biotreatment had the most filled pods; the filled pods' number /plants between treatments was not significantly different.The range of dry seed weight was 21 to 30 g/3 holes, and between treatments was not significantly different.The dry soybean seed weight produced reached 1.664-2.463t/ha (Table 2).In the LSD test with an actual level of 95%, alignments followed by the same letter do not significantly.

Discussion
The high population of armyworms has an impact on crop damage.Severe crop damage is caused by biopesticides and chemical pesticides that were sprayed and washed away by rain, so there is little visible effort to control them.However, the addition of adhesive is always provided during application.Heavy rain always falls after spraying, which occurs several times as long as the armyworm population in the field is high.Based on observations, the Anjasmoro variety is susceptible to attack by armyworms if compared to the Argomulya variety, which is currently also planted among oil palm plantations in the tidal areas of South Kalimantan.The effectiveness of biopesticides (NSP and NPV) to control armyworm attacks is comparable to that of chemical insecticides.At heavy armyworm attack intensity, chemical insecticides and biopesticides are less able to suppress plant damage; the crop damage intensity is still high (> 70%), moreover, the soybean variety planted was Anjasmoro which was susceptible to armyworms.One solution to this problem is planting resistant soybean varieties combined with other control technologies.Based on the reports, the role of armyworm-resistant varietal is very high in reducing crop damage.The suppression level of Degra 1 (candidate of resistant variety) on the attack intensity of armyworm reached 26%.The effectiveness of armyworm control increased to 35% when Degra 1 was combined with NPV bioinsecticides and was not significantly different from the combination of Degra 1 with chemical insecticides [17].Based on the information that in the area of South Kalimantan for the last two years, the population and attack rates of armyworms are very high, so to cultivate soybeans in that area, it is better to plant armyworm-resistant soybean varieties such as the Argomulyo soybean variety which is more resistant to armyworm attack than the Anjasmoro variety [14].
The effectiveness of controlling pods sucker with trap crops may be increased by planting trap crops with an area of 12 %, 6% of which was at the same time as planting soybeans, and the remaining 6% was seven days after planting soybeans.Increasing the planting area of trap crops by 6% and delaying planting time will provide an opportunity to increase the number of pod-sucking pests concentrated on trap crops.So, it is expected that damage to soybean plants due to attack by pod sucking can be suppressed as low as possible.Trap crops are grown in a limited area to attract insect pests in the planting area to protect the main crops from attack by these pests [18].The trap crop planting technique selects plant species with age variations (early, medium, or deep) that are the same or different from the main crop.Planting trap crops will reduce the frequency and amount of insecticide used.In Indonesia, the planting of mung beans of the Merak variety has been used as a trap crop for soybean pod-sucking pests [16].This technology only uses 6 to 12% of the soybean planting area.This action reduces insecticides by up to 90% because control is only carried out in the trap crop area.Nibouche [19], [20] reported that "Erianthus arundinaceus is a trap crop for the sugarcane stem borer Chilo sakharifagus (Bojer)"."Mung bean (Vigna radiatus L.) is a trap crop of Apolygus lucorum (Meyer-Dur.) to protect Bt-cotton" [21]; "velvet leaf Abutilon theophrasti (Medicus) can be used to trap Bemisia tabaci (Gennadius) and Sylepta derogata (Fabricius)" [22].In China, Bt-maize is proven as a trap crop for S. frugiperda control in agricultural systems, because it is preferred as an oviposition site.At the same time, plant damage is low, compared to conventional maize, millet, sorghum, soybean, wheat, and cotton crops [23].The highest seed dry weight was achieved in treatment no. 2 (Biopesticides-6x), but not significantly different from treatment no. 6 (Insecticides-6x) and no. 3 (Biopesticides-4x).The lowest seed weight was found in treatment no. 5 (Biopesticides-4x + mung bean trap crop), but not significantly different from treatment no. 4 (Biopesticides-6x + mung bean trap crop) and check, which is suspected to be due to the high armyworm attack so that it indirectly has an impact on the low dry weight of soybean seeds.

Conclusions
Leaf-eating caterpillars are important pests in soybean plants' vegetative growth phase, dominated by armyworms S. litura and leaf rollers L. indicata.
The critical phase of soybean plants against leaf-eating caterpillars is between the ages of 50 to 65 DAP.
The attack of leaf-eating caterpillars in the vegetative phase was very high, reaching 82%, but did not attack the pods.Bioinsecticides have equivalent efficacy to chemical insecticides in controlling leaf-eating caterpillars.Planting mung bean as a trap crop effectively in controlling the pod-sucking bug R. linearis on soybean pods.Dry soybean seed weight produced ranged from 2.069 to 2.463 t/ha, whereas in plots with trap crops, it ranged from 1.664 to 1.969 t/ha.

Figure 5 .
Figure 5. Percentage of dry mung bean seed weight affected by pod sucking and healthy at harvest.Tumih, Wanaraya District, Barito Kuala Regency, South Kalimantan.

Table 1 .
Attack intensity of armyworms, pod suckers, pod borers, and pod eaters in the seeds at 80 DAP.Tumih, Wanaraya District, Barito Kuala Regency, South Kalimantan.In the LSD test with an actual level of 95%, alignments followed by the same letter do not significantly.

Table 2 .
The number of harvested plants, the number of filled pods/plants, and the weight of dry soybean seeds at harvest.Tumih, Wanaraya District, Barito Kuala Regency, South Kalimantan.