Soybean is the main food crop after rice and corn, it has a high quality, balanced and complete protein. The increase in demand for soybeans in Indonesia in 2021 will reach 2.9 million tons/year, but domestic soybean production is only able to meet 40%, which means that 60% of market demand cannot be met by local producers at that time. The imbalance between market demand and soybean production is caused by many factors, one of which is the attack of plant pest such as armyworm (Spodoptera litura) [1].

Armyworm (Spodoptera litura) is a polyphagous pest capable of attacking soybean crops from the vegetative to generative phases. Yield loss due to S. litura attack can reach 85% and can even cause crop failure [2]. Farmers' efforts to control armyworms are still dominated by the application of chemical pesticides which are considered more effective and efficient in suppressing pest populations. As a result of the continuous application of chemical pesticides in plant cultivation practices, it can cause environmental damage. such as soil and water pollution, as well as disruption of ecosystem functions in cultivation areas, such as emergence of pest resurgence and resistance and death of natural enemies. The use of organic pesticides is an alternative that can be done because they come from natural ingredients that are easily decomposed so they do not cause environmental damage. Many plants have potential as pesticides, including papaya leaves (Carica papaya L.) and garlic bulbs (Allium sativum).

Papaya leaf are often used as an ingredient for organic pesticide it is also save for the enviroment because how easy for them to unravel. Papaya leaf contain papain enzymes and flavonoid compounds, alkaloids, saponins. Based on the research results of Siahaya and Rumthe [3], papaya leaf extract with a concentration of 40g/100ml is effective in controlling the Plutella xylostella on cabbage. Garlic plants (Allium sativum) especialy in their bulbs contain the compound Allicin which can interfere with the metabolism of insect pests according to some source. Based on research by Sabaruddin [4], garlic extract with a concentration of 120g/L can affect the intensity of damage by armyworm pests. The purpose of this study was to determine the effectiveness of papaya leaf extract and garlic against armyworm (S. litura).           

The research was conducted at the Plant Protection Laboratory, Faculty of Agriculture, East Java "Veteran" National Development University, it was conducted for 3 months from June 2022 to August 2022. This study used a Completely Randomized Design (CRD) with 7 treatments and repeated 4 times, in each repetition consisting of 10 test larvae. The treatment used is:

• P0: Control

• PP1: 10% (10ml papaya leaf extract solution + 90ml distilled water) 

• PP2: 20% (20ml papaya leaf extract solution + 80ml distilled water) 

• PB1: 10% (garlic bulb extract solution 10ml+90ml distilled water) 

• PB2: 20% (20ml+80ml garlic bulb extract solution)

• PPB1: 10% Combination 1:1 (5ml papaya leaf extract solution + 5ml garlic bulb extract solution + 90ml distilled water) 

• PPB2: 20% Combination 1:1 (10 ml papaya leaf extract solution + 10 ml garlic bulb extract solution + 80 ml distilled water)

Rearing S. litura

Rearing of S. litura was carried out to obtain uniform test insects, a cage measuring 50 x 60 x 70 cm that was covered in nylon thread was used as a breeding cage for the larvae and was fed castor or soybean leaves. The instar used was instar 2 and the number of test insects was 280.

Preparation of Papaya Leaf Extract and Garlic

The extraction of papaya leaves and garlic bulbs was carried out by providing raw materials which had been air-dried and oven- dried to obtain dry powder which would be macerated with 70% ethanol for 3 days. Extraction was carried out using a rotary evaporator with a temperature of 50oC then the extraction results were in a water bath so that the extraction could cool evenly.

Soybean Planting and Application of Organic Pesticides

Soybean seeds were planted in polybags of 21 clumps for 20 HST in the vegetative phase. Planting is done by preparing the planting medium in the form of planting soil and compost with a ratio of 3:1, the planting medium is distributed to 21 polybags with 1 polybag to be planted 3 soybean seeds. The soybean variety used is the Anjasmoro variety. The application of vegetable pesticides was carried out when S. litura was infested with 10 soybean plants (20 DAP) per treatment using a 100 ml sprayer.

Mortality Rate of S. litura

The mortality rate of armyworm (S. litura) can be determined by observation of the number of larvae that died after treatments. Observations were made every 24 hours until the armyworm died or turned into a pupa. Picking armyworms is done by mechanical means, namely taking by hand and collected in a container. According to Rusdy the Mortality rate is calculated using the formula:

• Z: Mortality Rate
• a: Number of dead armyworms
• b: Number of total armyworms

Lethal Concentration 50 (LC50)

Lethal Concentration (LC50) is a term used to test the effectiveness of a type of pesticide in pest control which can kill 50% of the test pest insects on observation. Probit analysis was used to determine the LC50 value of each treatment. According to Hendri et al. the relationship between the logarithm of the concentration of the test material and the probit value of the percentage of mortality in the test animals is a linear regression function with the formula:

Information

• Y: Mortality profit value

• a: Constant

• b: Slope

• x: Logarithmic concentration of the test substance

Morphological change between larvae after it was givin the pesticide and the one that act as control (Non - treatment) showed a remarkable result. The treatment larvae have its body undergo changes based on its appearance and color, its body shriveled, shrunken and have a yellowy too brownish color this indicate body decomposition probably caused by the pesticide. According to Moniharapon et al. [5], plant based pesticide contain a substance called flavonoid that inhibits the insect respiratory, while Nani [6], stated that papaya leaves contain an enzyme called papain that can hydrolise the insect exoskeleton this explain why the treatment larvae have a soft and mushy texture.

Figure 1: Morphological change on (A) S. litura as control; (B) S. litura after treatment

The results of the analysis of variance (ANOVA) showed that the application of organic pesticides in the form of garlic bulb and papaya leaf extract and their combination at two different concentrations as a whole showed a significant difference compared to the control on the percentage of armyworm mortality (S. litura) for six observation day (Figure 2). The results of the multiple comparison analysis or follow- up test using BNJ 5% presented in fig 2. show that the treatment was able to increase the percentage of S. litura mortality compared to controls during the 6 days of observation. The best treatment was shown by PP2, namely a single application from papaya leaf extract at a concentration of 20%, with a mortality percentage in the 1st to 6th observation respectively of 6, 11, 12, 13.75, 14 and 14%.

The success of plant based pesticide is influenced by the type of raw material it used, test insects and environmental factors. Siregar et al. [7], stated that environmental factors are the main factors that influence environmental effectiveness because most organic pesticides use water as a solvent so they evaporate easily if given during the day. Siregar also stated that giving the pesticide is better used in the morning where the stomata The leaves of the plants open so that they can be absorbed into the leaves.

Irfan [8], states that organic pesticides have an effectiveness level that is almost the same as chemical pesticides but has a short storage time so they cannot be stored for too long and are disposable. Irfan also states that to achieve the same level of effectiveness as chemical pesticides it need a high level of concentration. Sadewo's research [9], showed that the results of 20% administration of breadfruit leaf extract (Artocarpus altilis) were able to control the fruit fly larvae population of Bactrocera sp. as much as 83.3%. A study by Suryadama et al. [10], showed that giving 10% plant based pesticide derived from different ingredients againts cabbage pest (Plutella xylostella) gave different results and the most effective was tobacco leaf extract.

The ability of pesticides to kill test insects can be done through various approaches, one of which is Lethal concentration (LC50) which is the concentration required for pesticides to kill 50% of test insects, in this case S. litura, which is measured based on its probit value. The LC50 of each organic pesticide from papaya leaf extract, garlic bulb and a combination of the two was 16.90%, 20% and 18.60%, respectively, while the correlation value (R) between pesticide ingredients on mortality showed a correlation value (R) close to 1 means the relationship between the two variables is very strong (Figure 2).

Figure 2: Mortality of S. litura on Each Treatment

Figure 3. Probit Analysis Graph Between Log10 of Concentration and Probit Value Againts S. litura

The efficiency of probit analysis is measured by the amount of raw materials used while its effectiveness is measured by the amount of mortality it produces, the main factor influencing probit analysis is the various insect cuticles. The cuticle is the outer layer of an insect which is composed of chitin. Putri et al. [11], stated that the cuticle on S. frugiperda was 0.2 – 0.5% on its first stage of development (1st–3rd instar). Probit results varied depending on the type of raw material and test insects used. Mutaali et al. research [12], showed that giving beluntas leaf extract (Pluchea indica) to S. litura resulted in an LC50 of 28%, research by Hasyim et al. [13], showed that administration of the entomopathogenic fungus Metarhizium anisopliae to S. exigua produced an LC50 of 1,189.83 ppm, Wangi et al.'s research, [14], showed administration of citronella essential oil extract (Cymbopogon nardus L.) to S. frugiperda produced LC50 by 8.6%.

Based on the results obtained from the above, it can be concluded that the application of vegetable pesticides based on papaya leaf extract, garlic bulb and the combination (papaya leaf + garlic bulb) can be used as an organic pesticide. The LC50 toxicity obtained was papaya leaf extract 16.90%, garlic extract 20% and a combination of papaya leaf extract + garlic 18.60%.

Acknowledgment

data The author expresses his gratitude to various parties for their invaluable assistance, guidance and advice, namely to Dr. Ir. Wiwin Windriyanti. MP. and Drh. Wiludjeng Widajati, MP as the author supervisor.

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