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ISSN : 1598-5504(Print)
ISSN : 2383-8272(Online)
Journal of Agriculture & Life Science Vol.53 No.2 pp.153-162

Development of a Plum (Japanese Apricot) Seed Crusher to Control Harmful Larvae (Eurytoma maslovskii) in Plum Orchard

Mohammod Ali, Bok Seok Kim, Seong-Jin Park, Hyuck-Joo Kim*
Department of Industrial Machinery Engineering, College of Life Science and Natural Resources, Sunchon National University, Suncheon, 57922, Korea
Corresponding author: Hyuck-Joo Kim Tel: +82-61-750-3268 Fax: +82-61-750-3260 E-mail:
December 26, 2018 February 20, 2019 March 12, 2019


The Eurytoma maslovskii conduces the unexpected plum dropping. It stayed overwinter inside the pits of the dropped plums and able to oviposit on plum surface when the diameter of the plums are over 16 mm prior to endocarp hardening. To control this harmful pests is too much essential to plum orchard. Therefore, the plum seed crusher (PSC) was designed and developed according to the purpose of perishing the pests through destroying the dropped plums. The rocks and the weeds were removed from the plum orchard prior to the test. Manually operated plum seed crusher picked-up the dropped plums from the ground and crushed them. The performance of PSC was evaluated by applying 2.5 and 3.0 km/h travelling speeds, and controlling the gaps; 18, and 28 mm intervals between plum pick-up discs. The test result showed the plum pick-up rate was 98±2.0%, and 92±5.3% with the machine travelling speed of 3.0 km/h in laboratory. Further, it changed to 95±8.7%, and 93±5.8% when the travelling speed was used 2.5 km/h. In both cases of test plum pick-up discs were maintained 18 mm, and 28 mm gap intervals, respectively. Furthermore, in field conditions, pursuing to similar gap intervals, the plum pick-up rate was 94±4.0%, and 92±2.0% with the speed of 3.0 km/h albeit it showed 92±4.0%, and 90±3.5% when the speed was decreased to 2.5 km/h. The maximum plum pick-up rate was found at 18 mm disc intervals with 3.0 km/h travelling speeds. The crushing teeth were selected 8 mm in height by repeated test to destroy the plum seeds. The result showed 100% crushing efficiency was facilitated to entire tests at 280 RPM crushing speeds regardless of plum sizes and shapes. This machine is preferred for the farmers to control the damage of plums by preventing the propagation of the identified pests.


    Sunchon National University


    Plum (Prunus mume) is an Asian tree species, popular in worldwide as Japanese Apricot and Chinese plum. It’s widely cultivated in southern china, Japan, Korea, Taiwan and Vietnam (Fang et al., 2006). Korean name of this fruit is maesil. More or less plum tree grows in every provinces of South Korea, Jeollanamdo province cultivates plum about 45.7% of its total cultivated area and Gwangyang city of this province was produced 28% of the country’s total plum production (Lee et al., 2011).

    This deciduous plum tree starts flowering in the early spring and is harvested in late May to mid-June in South Korea. Plum exists in a wide varieties with different sizes and colors. The young Japanese apricot shell is light green and at the time of ripening it seems to yellowish with sour in tests. It is too healthy and economic fruit. Plum fleshes and seeds quietly help to prepare various kinds of post processed products that have highly monetary values (Ali et al., 2017). As a medicinal fruit it makes free from various diseases, like; fever, diabetes, fatigue, coughs, diarrhea, and effective at relieving blood fluidity (Chung et al., 2013).

    E. maslovskii attacking plums and creating a serious problem to plum orchard in Jeollanam-do province. It has been revealed the enormous damages of plum that ultimately reduced the maximum yield of plums. The plums were injured in this province except the coastal areas. The extreme damaging rate of plum was 67% in 2013 and 33.3% in 2014, respectively. The year-round life cycle of E. maslovskii are started after laying eggs in the nuclear tissue of Japanese apricot seeds. Before the ovary of nuclear appetite is formed, the caterpillar lay eggs and then transform into a mouth-mouth larvae, ingesting endosperm, turning into a pupa and wintering, and fascinating as an adult in the early spring of the following year (Choi et al., 2015).

    The larvae of this caterpillar spawn on the plum and wintering from the plum ovary to the domesticated larvae. The survival rate was less than 30% after passing through the rainy season in July to August. To spray a control agent (2~3 times) in the beginning on mid-April at 5 days intervals could be the most effective method for controlling these pests (Choi et al., 2015). Although this methods has been used but being chemical agent it couldn’t properly fit to the environment. On the other hand, pupation of this mature pests took place between late March and late April. So, more than 90% of the adult wasps emerged between late April and early May. However, by observing the life cycle of the wasp, it is noticed that most of the damaged fruits would have fallen in the month of early June. It happened exactly before the plum harvesting period (Lee et al., 2014).

    Therefore, one of the way need to be developed to prevent these pests which have been causing massive damages since 2013 in the plum farms of Suncheon, Chunnam and Gwangyang areas. A proper developed plum seed crusher would be the suitable and permanent solution to combat with the pests without declination of environment. Therefore, the objective of this study is to develop a plum seed crusher to destroy the harmful larvae by collecting and crushing the drop-out plums at the ground in the plum orchard.

    Materials and Methods

    1 Design and descriptions of plum seed crusher (PSC)

    The plum seed crusher was designed and developed considering the weight and safety of the machine, size of plums and plum orchard, the working environment and convenience of workers. By calculating the needed power, a small two-stroke gasoline engine was selected as the power source for the developed machine. It can work in plum orchard mixed with flat and sloped lands. PSC was mainly assembled owing to multifunctional purposes that continuously collected and crushed the dropped plums and discharged the pulverized plums directly to the ground. The schematic diagrams of the plum seed crusher are shown in Fig. 1.

    2 Plum collector

    To collect the dropped plums an effective plum collecting system is prerequisite. Recently, a prototype jujube collector has been used in Suncheon jujube orchard. The Korean intellectual property office (KIPO) has already registered this simple jujube collector (Model No. 20-2012-0002298) which is available in the market (Fig. 2A). This type of collector was purchased from the market, modified and some components were further added owing to fabricate a plum seed crusher (PSC) machine.

    The modified plum collector was used for collecting the dropped plums in the plum orchard. The total width of plum collector was 330 mm. An attaching frame, pick-up discs, pick-up bars, and collecting buckets were the main components of plum collector (Fig. 1A). The pick-up bars were used as plum collector. It was made by resilient synthetic resin. The end portion of these pick-up bars were used to hold the dropped plums. They were attached to the pick-up discs. Eighteen pick-up discs were used for the test where every disc contained sixty three pick-up sticks (Fig. 2B).

    3 Plum crusher

    Plum crushing base frame consists of two support bars, support plate, crushing roller and pulley, timing pulley, baseplate, and a two-stroke gasoline engine (Fig. 1B). The engine was placed on the baseplate at the front of machine. Total weight of PSC could be reduced using lightweight steel. Plum collector and crushing unit were combined through steel rods (Fig. 1, Fig. 3).

    4 Working principle and operational control of plum seed crusher (PSC)

    The plum seed crusher accomplished the entire work through the plum collecting and crushing. Plum collector of PSC collected dropped plums by pick-up bars and gathered into the den of crusher. Then, crushing roller crushed the plums continuously. To crush the collected plums the roller of the crusher received the power from the loading engine through appropriate deceleration including gear reduction and chain power transmission systems. A 1.4 HP twostroke gasoline engine Tb-26 (Mitsubishi Co., ltd, Nagoya, Japan) was used as power source for plum seed crusher. The supplied power was sufficient to perform the operations of the machine. In order to drive the roller crusher, at first, engine crankshaft rotated and decelerated by a spur gear. Secondly, the engine power transmitted to the roll crusher through a chain sprocket and pulley. The power of the engine was set at about 6,000±1000 RPM and the reduction ratio was 25: 1. However, by this speed of engine and the reduction ratio, the final rolling crusher rotated into 200 to 280 RPM. After crushing, plum seed crusher discharged plum residues directly towards the ground and moved on without stoppage. It has been found that foreign substances such as rocks are coll- ectively collected at the time of collecting plums. Especially when the size of the rock is large, continuous operation is impossible due to the interruption of work, breakage of the crushed blade or scattering of the rocks. Therefore, the rocks and other unnecessary materials were removed from the plum orchard then crushing and discharging tests were conducted.

    5 Selection test for effective crushing teeth

    The crushing roller designed with various symmetrical crushing teethes. The plum crushing rate and fracturing effects of crushing teeth depended on the clearance between the crushing teeth and the support plate (Fig. 1B). Therefore, a factorial test was executed with 1 kW single-phase motor (1700 RPM) as the power source in view to design the effective teeth height. However, different teeth height of crushing blade such as, 4 mm, 6 mm, 8 mm and 10 mm were selected for the test, respectively. Selected teeth height was designed and assembled with the crushing roller at regular intervals so that the plums can be effectively broken (Fig. 4).

    6 Performance test of PSC in laboratory and field condition

    Pick-up type plum seed crusher was tested using experimental plums. The length and width of selected plum diameters were around 22 to 38 mm. 300×40 cm area was chosen for laboratory and field test of PSC. Vinyl sheet was placed on the floor in the laboratory. The area was marked up and the plums were scattered inside the area (Fig. 5A). The plum seed crusher was manually operated. It maintained the selected travelling speeds and disc to disc distances. The calculating travelling speed was 2.5 and 3.0 km/h and the disc to disc distances 18 and 28 mm were used separately for each test. On the other hand, field test of PSC was carried out at Gyewol plum orchard under Suncheon city (Fig. 5B). Generally, plum orchards in this area being irregular shape in size and unclean from rocks and weeds. However, the plum orchard was needed to clean and marked up the testing area prior to the test. Therefore, large, medium and small rocks were collected from the farm field and removed the weeds using weed remover. After cleaning the experimented area, plums were outstretched on the ground and tested the machine performances. Plum pick-up and crushing test data was compiled, recorded and observed. In this test, pick-up ratio, plum crushing rate and travelling speed were identified as equation (1)-(3). Every test was conducted at least three times with one hundred and fifty samples. The field test based on travelling speeds and the disc to disc distances were similar to the laboratory test.

    The formula used in this study is as follows:

    Plum pick-up rate (%)= Number of picked up plum Total dropped plum ×100

    Plum crushing (%)= Number of crushed plum Total picked up plum ×100

    Travelling speed (km/h)= Distance Time

    Results and discussion

    1 Evaluation of crusher teeth for effective plum seed breakage

    The rotational effects of the crushing roller, the clearance between the crushing roller and the supporting plate, the size of the crushing blade and selections of their teeth height were experimentally observed. Fig. 6A is showing the relationship between the plum seed crusher used various sizes teeth to execute plum crushing rate. When the size of the crushing teeth was 4 mm, the collected plums were partially destroyed and the crushing rate was found below 40%. After increasing 2 mm height of teeth, it showed 60% crushing rate. In both cases many plums were passed without crushing due to more gap between the crushing rollers and supporting plate. The result showed 100% crushing rate was facilitated when the teeth height was in the range of 8 mm ~ 10 mm. For the developed plum seed crusher 10 mm height of teeth was the maximum size of the teeth and it was not perfect for crushing plum in this machine due to clearance fitting problem. In this situation the 8 mm teeth height was selected and considered to the effective crushing of plums. After setting the 8 mm height of crushing teeth, about 1.1 mm clearance found between the crushing teeth and the supporting plate of the machine. This little clearance helped to crush the plum seeds properly and destroyed Eurytoma maslovskii larvae (Fig. 6B).

    2 Performance test results of PSC in laboratory

    Experimental plums were used to evaluate the performances of plum seed crusher in the laboratory (Fig. 7). The results of the test are shown in table 1. When plum pick-up disc to disc distances were fixed at 18 mm, the plum seed crusher was able to pick-up 95±8.7% of plums in 2.5 km/h travelling speed whereas when the disc to disc distances were fixed at 28 mm, the pick-up rate was 93±5.8% in same travelling speeds. This result showed, when the disc to disc gap increased the performance of plum pick-up was decreased. At the same time, the crushing roller was turning into the speed of 280 RPM and all of the collected plum seeds were successfully broken using this speed. On the other hand, when the travelling speed of PSC was converted to 3.0 km/h, it showed 98±2.0% and 92±5.3% pick-up rate in the condition of 18 mm and 28 mm gap between two pick-up discs, respectively. About 6% collection of plum was reduced due to 10 mm extra gap among the discs, but 100% crushing rate was facilitated with same speeds of crushing roller (Table 1).

    3 Field test results of PSC in plum farm

    The actual harvesting rate of plum seed crusher was depended on the topography of the plum farm. The performance test of PSC was highly correlated with weed and rock management in plum field. It was considered as important factor, because of the weed condition under the plum tree and its size effect on the collecting and crushing rate. On the other hand, some foreign substances such as large rocks can create the problems during plum crushing (Fig. 8).

    The plum seed crusher successfully picked-up and crushed the dropped plums in the field condition (Fig. 8). Table 2 is showing the results of the performance test of the plum seed crusher in the field. The pick-up rates of PSC were changed in different speeds. When the disc to disc distances were fixed 18 mm, the pick-up rate of PSC was 94±4.0% in the speed of 3.0 km/h, which was the maximum pick-up rate in the field conditions. In the same disc arrangements, when the machine speed was reduced and fixed at 2.5 km/h, it showed 92±4.0% pick-up rate of fallen plums. On the other hand, when the disc distance was changed from 18 mm to 28 mm the pick-up rate was 92±2.0% and 90±3.5% for the speed of 3.0 and 2.5 km/h, respectively. In addition, the test result showed the field condition pickup rate was 3~4% less than laboratory conditions. It occurred due to the topography of the plum field soil. Some plums were put into the hole of soil surface and PSC failed to pick-up them, for that reasons the collecting rate of PSC was lower than laboratory. Although the crushing rate of both conditions were found 100%.

    As described above, there had been focused a problem for plum crushing period that was foreign substances such as rocks in the plum orchard. In period of test, different sizes rocks were found. Up to 70 mm in height and 50 mm in wide rocks classified as large in size. Also, around 40 mm height and 25 mm wide rocks marked up as medium size. Albeit the dimension less than 15 mm height and wide based small size rocks were disabled to make problems during the tests. On the other hand, the PSC failed to pick-up larger sized rocks due to their bulky sizes and weights. Only some of medium sized rocks length and width ranged below 28 mm had possibility to pick-up in the collecting bucket. Particularly, the rocks occurred the interruptions of the operation, had possibility to break the crushing blade and scatter of the rocks. However, the plum orchard needed to remove from weeds and rocks prior to the test for avoiding unexpected results. Although, when a rolling crusher found strong foreign matters such as rocks the usable engine could be automatically stopped. Thereby it helped to enhance the safety of the operator, prevent the impact of the roll crushing blade, and improve machine durability.

    The above results shows that the PSC were satisfactory for perishing the E. maslovskii larvae from the plum orchards. The developed plum seed crusher can effectively remove the harmful pests physically, which means it is possible to prevent the propagation of this pest. And, a wide use of PSC could ensure the maximum yield of plums that would help to hold their values among the plum farmers, traders and entrepreneurs.


    This work was supported by “Academic Research Support Program” of Sunchon National University, Republic of Korea.



    Schematic diagram of A: the main parts of plum collector; B: base frame of plum seed crusher; and C: the combinations of plum collector and crusher.


    A: Fallen plum collector purchased from the market; B: plum pick-up disc with pick-up bars.


    A-B: Two views of developed plum seed crusher (PSC).


    A: Crushing roller with symmetrical crushing teeth; B: photo of plum crushing test.


    Pictures of A: laboratory; and B: field testing process of plum seed crusher.


    A: Graphical representations of plum crushing rate (%) using various crusher teeth height (mm); B: picture of crushed seed.


    Pictures of PSC laboratory test; A: picked-up; and B: collected dropped plums.


    Pictures of field test; A: pick-up; B: collecting; and C: crushing test of dropped plums.


    Laboratory test results of plum pick-up and crushing rate in respect to pick-up discs gap and travelling speeds

    Field test results of plum pick-up and crushing rate in respect to pick-up discs gap and travelling speeds


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