Diversity Of Insect Pests In Rice Plant (Oryza Sativa L) in The Rice Fields Of South Kualuh District, North Labuhanbatu

Eradicating rice pests in South Kualuh is difficult to do optimally, because most farmers do not understand the types of pests that attack their rice plants. The objective of this study was to obtain information about the type of pest insects in rice plants and to find out the diversity index of insect pests in rice plants. This research was conducted using trap method and collection of insects was done using a insect net. Observation data was analised using Shanon Wiener (H) diversity / diversity index. The result showed 13 types of pest insects which belongs to 10 families. That is Tettigonia sp.(Linnaeus, 1758), Sogatella furcifera (Horváth, 1899), Nephotettix virescens (Distant, 1908), Cofana spectra (Distant, 1908), Atractomorpha crenulata (Fabricius, 1793), Erotides sp.(Laporte, 1836), Leptocorisa acuta (Thunberg, 1783), Aulacophora indica (Gmelin, 1790), Chrysochus cobaltinus (LeConte, 1857), Silba capsicarum (McAlpine, 1956), Hercostomus germanus (Wiedemann, 1817), Cnaphalocrosis medinalis (Guenée, 1854), Scirpophaga incertulas (Walker, 1863). The diversity index of rice pest insects was categorized as moderate with a value of 2,35 and a dominance index of 0,108. This value indicates that the distribution of species is evenly distributed so that no

https://ijstm.inarah.co.id sample bottles, tweezers, labellingstickers, microscope, loup, petri dish, tape meter, thermometer, hygrometer, and cotton. While the material used in this study is alcohol 70%. The insectswere collectedusing the trap method which uses insect net as its main tool. The equipment used is insect nets, where the procedure is based on taking samples of insect pests caught by the insect nets by determining 3 observation locations in the rice fields. The insects were obtainedby using insect net footage on the rice field. This process was carried out at 3 different locations with each sampling location area of 200 m 2 The insects obtained from 3 locations were then taken to the laboratory to be observed based on the morphological characteristics and identified according to their species using an insect identification guidebook. The results obtained were analyzed using the Shannon-Wiener formula: H '= -∑pi ln pi; pi = ni / N. The magnitude of the dominance index value of each insect pest group is calculated using the formula from Simpson (1949): C = ∑ (ni / N) 2

III. RESULT AND DISCUSSION
Based on the results of research that has been carried out, there are3 observation locations, which are location I isat the adjacent to the highway, location II is in the middle of rice fields, location III is at the adjacent to residential areas, obtained 13 types, 10 families, and 5 insect pest orders on rice plants in Kualuh Selatan District. North Labuhanbatu Regency. The types of insects obtained are in table 1.  I there are 411 insects, 488 insects at location II, and 416 insects at location III. The highest number of insects found is at location II. Meanwhile, the least number of insects was found in location I. The highest number of individual insects is found in location II, because location II was in the middle of rice fields. This location is an ideal place for insects because it is not affected by the outside environment such as roads and residential areas. In addition, the humidity at location II is also https://ijstm.inarah.co.id more humid than the other two locations. Location I had the least number of insect pests due to the location of the location which is on the edge of the main road. The rate of human transportation activity and air pollution can affect the development of insects. According to Odum (1996), a polluted ecosystem environment will have diversity disturbances which can affect the reduced number of species diversity in the area.
Based on the results of research from three observation sites, 13 species of rice plant insects were found, including Leptocorisa acuta Thunberg, Aulacophora indica Gmelin, Cofana spectra Distant, Nephotettix virescens Distant, Sogatella furcifera Horvath, Silba capsicarum McAlpine, Scirpophaga interculas Walker, and Tettigonia sp. The insect pest species that had the highest number was Sogatella furcifera with a total of 244 individuals. Meanwhile, the insect pest species that had the least amount is Tettigonia sp. with a total of 18 individuals. The families found consisted of Tettigoniidae, Delphacidae, Cicadellidae, Pyromorphidae, Lycidae, Alydidae, Chrysomelidae, Lonchaeidae, Dolichopodidae, and Pyralidae. The family with the highest number of pests from the research results was the Cicadellidae with the types of Nephotettix virescens and Cofana spectra. The family that has the least number of pests in rice fields is the Tettigonidae family.
Rice is the perfect host for some herbivore species. All parts of the rice plant can be eaten by herbivorous insects, the parts that are mainly eaten are young rice grains, stems, roots and leaves (Jumar, 2000). The Tettigonidae family has the least number due to the low diversity of plants in the rice fields which affects the availability of food sources. In addition, the presence of predators also affects the pest population of this family. Overall at the three locations the same species were found, although the observation locations were different. This is presumably because the insects found are species that specifically get food from rice plants. According to Rismunandar (1986), there are similarities in the species of pests that attack rice plants, even though the areas are different because of their food supplies and distribution capabilities. There are pests that attack according to the phase of development of the rice plant, therefore pests are found from the beginning of growth to harvest of the crop. Diversity Index and Dominance Index Evennes Index(E) -0,91 Based on the results of data analysis, at location I, the index of insect pest diversity (H ') was 2.32 with a dominance index value (C) of 0.11. The value (H ') indicates that the insect pest diversity index at location I is classified as moderate. Odum (1996) explains that diversity is identical to the stability of an ecosystem, that is, if the diversity of an ecosystem is relatively large, the condition of the ecosystem tends to be normal. Ecosystem areas that have diversity constraints tend to be moderate, on the problematic ecosystem areas that are polluted usually have a decrease in the diversity of species.
Meanwhile, the dominance index (C) at that location is categorized as low. This case shows that there are no species that dominate in that location. This is in line with the opinion of Odum (1996), the dominance index <0.50 means that there are almost no species that dominate (low), the dominance index value> 0.50 -<0.75 means the dominance index is moderate, while> 0.75 to close to 1 means that the dominance index is high. -0,90 Based ontable 3, the calculation results show that the diversity index value (H ') at location II is 2.32. This value shows the diversity index value (H ') at location II of 2.32. This value shows that the diversity of insect pests in that location is categorized as medium. This matter is consistent with the opinion of Soegianto (1994) that a community has a large diversity of species if the community consists of many species, on the contrary, if the community is composed of a few species and only a few dominant species, then the species diversity is low. https://ijstm.inarah.co.id As for the dominance index (C) at that location, the value is 0.11. This value indicates that the dominance index (C) of rice insect pests in that location is low. Similar to location I, there are also no species that dominate at location II. This is because in the generative phase of crop, the farmers increase the application of pesticides to reduce the rate of insect populations in rice plants. According to Fitriani (2016), the use of pesticides can reduce the population of natural enemies and non-target creatures. This matter can cause a decrease in species diversity in the agricultural ecosystem.  Saragih (2008), there are 3 categories of species diversity index values, namely, if H '<1 then the diversity is categorized as low, if H' 1> 3 then the diversity is categorized as medium, if H '> 3 then the diversity is categorized as high. The dominance index (C) in that location is 0.10 which is classified as low.
The results of the calculation of the evenness index (E ') for the type of density in the location III is 0.93. According to Azis (2015), if E '<0.50, then the community is in a depressed state. If 0.50 <E '<0.75 then the community is in a stable condition while 0.75 <E' <1.00 then the community is in an unstable condition. The evenness index value (E ') shall describe the stability of a community. The smaller the value of E ', so that the spread of organisms in the community which is dominated by certain species is not comprehensive and the opposite is the greater the value of E' or closer to one, so that the organisms in the community will spread out as a whole.
The evenness index (E ') at location III has a value that is almost close to 1, which indicates that rice cultivation in location III has a slightly higher value than the other two locations. This means that the rice plants in location III have a higher and more even distribution of individual insect pests. This is related to the increasing number of nutrient sources and hosts around the observation field that can be used to sustain their life. Based on the data in table 4, the diversity index (H ') value of insect pests in rice plants at location III is https://ijstm.inarah.co.id 2.39. This value indicates that the diversity index at that location is moderate. According to Saragih (2008), there are 3 categories of species diversity index values, namely, if H '<1 then the diversity is categorized as low, if H' 1> 3 then the diversity is categorized as medium, if H '> 3 then the diversity is categorized as high. Meanwhile, the dominance index (C) in that location is 0.10 which is classified as low.
The results of the calculation of the evenness index (E ') for the type of insects in rice plants at location III were 0.93. According to Azis (2015), if E '<0.50 then the community is in a depressed state. If 0.50 <E '<0.75 then the community is in a stable condition while 0.75 <E' <1.00 then the community is in an unstable condition. The evenness index value (E ') can describe the stability of a community. The smaller the value of E ', so that the spread of organisms in the community which is dominated by certain species is not comprehensive and the opposite is the greater the value of E' or closer to one, so that the organisms in the community will spread out as a whole. The location of location I is a rice field which is directly adjacent to the main road. Dense human activity and the incessant speed of transportation near these locations have reduced the diversity of insect pests. The average value of the air temperature at that location is 29.3 ° C with an air humidity of 57.7%.

Environmental Physical Factors at Research Site
Location I has an average air humidity value that is lower than the other two locations. The low humidity of the air also affects the insect pest population. Humidity is an ecologicalaspect, which means that it affects the activities of organisms and prevents their spread. Insects need air humidity for their bodies which is usually obtained from the air and plants that have water (Mahmudah , 2018).
Location II is in the middle of rice fields. The average air temperature at that location is 30.3 ° C with an average humidity value of 60.6%. Air humidity at location II is the highest compared to the other two locations. This is because location II is in the middle of a rice field area so that it is not affected by the outside environment such as roads and residential areas. Temperature and humidity affect the diversity of insect pests. This matter is in accordance with Jumar (2000), which states that insects have a certain temperature range where they can live.
Location III is a rice field area directly adjacent to residential areas. The range of average air temperature at that location was 29.2 ° C followed by an average humidity value of 58.3%. Air humidity at location III is lower than location II. Temperature can influence insect activity and development. Humidity will affect the evaporation of insect body fluids, insect preferences for living and hiding places.
Based on the results of data analysis, from the three locations obtained a pest insect diversity index (H ') of 2.35 with a value of dominance (C) is 0.108. Value (H ') indicates that the diversity index in the research location is moderate. Meanwhile, the value (C) indicates that the dominance index in that location is low. Diversity index is included in a moderate condition due to the large number of insect species and their even distribution. Besides being influenced by environmental physicochemical factors, it is also caused by the presence of predatory insects. Another factor is the existence of a competition between insects that affects the diversity of insect species. Human activities such as applying insecticides can also affect the diversity of insects.
The abundance of species in insects is determined by their reproductive activities supported by an appropriate area and meeting the needs of food sources. Seasonal changes greatly affect food availability, reproductive activities and insect survival skills which directly affect abundance. The results of measurements of weather temperature at the research location ranged from 27-32 ° C. According to Jumar (2000), the efficient temperature range for insects is a minimum of 15 ° C, an optimum of 25 ° C, and a maximum of 45 ° C. This indicates that the air temperature at the location has not reached the maximum limit so that the insects can still breed well.