Biodiversity of herbivorous insects in rice organic and inorganic ecosystem

Since many years, presence and activities of herbivorous insect very crucial in the agricultural ecosystem. Purpose of the research is to study biodiversity of herbivorous insect in the rice organic and inorganic ecosystem. The research was conducted in Salassae village, Bulukumba Regency, South Sulawesi from June to August 2021. The herbivorous insect from organic and inorganic ecosystem was carried out and identified at the Pest Laboratory, Department of Plant Pest and Diseases, Faculty of Agriculture, Hasanuddin University Makassar. The places used in the research divided into organic and inorganic rice ecosystem, with measurement 25 m x 25 m, respectively. The insect samples collected used ubinan system methods with diagonal intersection applied for pitfall trap. The samples from organic and inorganic ecosystem analyzed by Shannon-Wiener Index Diversity. The result of Shannon-Wiener Index was showed the higher number of herbivorous insects in the inorganic rice ecosystem (H’ = 1.71) with population about 391 individual (51%). In contrast, result of organic ecosystem (H’ = 1.68) lower than inorganic. Conclusion of the research: 1) the higher number of herbivorous insects in the inorganic rice ecosystem (H’ = 1.71), the lowest result from organic ecosystem (H’ = 1.68); 2) the highest rice harvest higher the organic ecosystem (297 kg) and the lowest in the inorganic (279.2 kg).


Introduction
Rice is the very important crop in Asia and few countries around the world.About 90% of rice growth and consumption in many countries majority located at South-East Asia [1,2].Increasing number of people has strong relationship with demand of food, clean water, housing, education etc.The rice production in the world wide have been influencing by presenting of pests and plant diseases as the key factor caused harvest loss.Pest insects as the main problem in the rice ecosystem because they are faster develop, unpredictable moving to another areas and very destructive.In general, the human effort manage presence of insect pest insect using chemical pesticides as the famous methods and very effective for insect control around the world.The chemical or synthetic insecticides potential caused pest insect resistance, resurgence, poisoning in the environment as the way endangered status of natural enemies [3,4].This is the real fact of chemical compound applied in the environment, they are very dangerous as contribution source causing pollution to water and soil [4,5].
Organic farming as the method planting rice without contribution of chemical compound on the field.The methods focused on minimalize negative effect used chemical compound to the ecosystem.The characteristic of organic farming such as: commonly use the local variety, natural fertilizer and 1230 (2023) 012068 IOP Publishing doi:10.1088/1755-1315/1230/1/012068 2 pesticides for environment sustainability.Organic farming based on ecofriendly management because the methods improving healthy environment and giving benefit in the agricultural sector [5,6,7].Planting rice used organic technique giving more benefit to environment with easy material degradable into ecosystem.The development of organic farming contributing field and human resources.Type of field as the important things in the agricultural activity and indicator quality of environment.Evaluation of field resources need to know the suitable of field and their limiting factor of development.The criteria of organic based input for the soil and processes inside with ecofriendly methods.In contrast with organic farming, inorganic allowed apply of pesticides and input of chemical fertilizer [2,8,9].Purpose of the research is to study biodiversity of herbivorous insect in rice organic and inorganic ecosystem in South Sulawesi.

Methodology
The research was conducted in Salassae village, Bulukumba Regency, South Sulawesi, Indonesia from June to August 2021.The places used in the research divided into organic and inorganic rice ecosystem with measurement 25 m x 25 m, respectively.After tillage of the field, preparing rice for nursery.The research used rice seed Berlian variety.This variety is resistant for pest and disease based on farmer experiment.About 30 days after planting, in the inorganic ecosystem applied by chemical pesticides (insecticide, herbicide) based farmer schedule.Especially organic ecosystem free from chemical products.

Pitfall trap observation
The herbivorous insect samples collected used ubinan system methods with diagonal intersection applied for pitfall trap.The field observation of research was 8 times started when rice 14 days after planting.Pitfall traps were made from plastic glass (diameter = 7 cm, height = 10 cm), filled with water mixed liquid detergent.The distance among trap was one about 1 m.The pitfall installation in the soil was carried out in the morning (07.00am) at the organic and inorganic for 24 hours.The top of pitfall covered with banana trees to prevent rain water enter the traps.The observation has interval 7 days after planting until harvest.

Identify of herbivorous insect
The herbivorous insect collected from inorganic and organic ecosystem was carried out at the Pest Laboratory, Department of Plant Pest and Diseases, Faculty of Agriculture, Hasanuddin University.The samples from organic and inorganic analyzed used Shannon-Wiener Index Diversity (H').

Result
The result of Shannon-Wiener Index was showed the higher number of herbivore insects in the inorganic rice ecosystem (H' = 1.76) with population of herbivorous about 391 individual (51.2%).In contrast, result of organic ecosystem (H' = 1.68) lower than inorganic ecosystem.Also, population of herbivorous insect 372 individual (48.8%).After few weeks of observation, time of rice harvest was arrived.Rice harvest result from organic and inorganic ecosystem was showed in figure 1, the highest harvest from organic ecosystem (297.6 kg) and the lowest from inorganic (279.2 kg).

Discussion
Since many years ago, the presence and activities of herbivorous insect very crucial in the agricultural ecosystem.The result of Shannon-Wiener Index in this research was showed higher number of herbivore insects in the inorganic rice ecosystem (H' = 1.76).The dominant insect pest in the organic and inorganic ecosystem is Leptocorisa (Hemiptera: Alydidae).Oxya (Orthoptera: Acrididae), Nephotettix virescens (Hemiptera: Cicadellidae) and Scirpophaga (Lepidoptera: Crambidae).Commonly herbivorous insect living in the field before farmer started growing the new plant.The previous research [2,10] reported that insect pest has ability to survive in the alternative host such a grasses around the rice ecosystem.The highest population in inorganic ecosystem with applied of chemical insecticides indicated symptom resistance of insect.Chemical treatment in long time will be good stimulus of insect forming adaptability or survive to environment.Also, synthetic pesticides application will lead to killing natural enemies in the same ecosystem with the pest.Not only using chemical pesticide in field will impact to organisms, but chemical fertilizers will giving negative feed back to environment.The fertilizers will changed the soil structure, reduce number of beneficial microbes that useful for plant growth and lost of natural nutrition that original from the soil.The another researcher [8] reported the seed difficult growth on the soil contain many residue of chemical herbicides.The top root of young plant cannot penetrate deeply into the soil.It is possible causing plant growth in abnormal condition.
In contrast, result of organic ecosystem (H' = 1.68) lower than inorganic.The lower number of herbivorous insect in the organic ecosystem assumed many insect natural enemies working well in the habitat.The availability of insect pest in the organic ecosystem that free from pesticides as the best place living for arthropods.Previous research [2,4,6,10] reported that synthetic pesticides application will losing or killing of natural enemies as biological agents in the rice ecosystem.Biological control is very safety methods for serving the best agricultural product that increasing health of consumers and free from pollutant.Farmers can help more increasing number of biological agents with manage the flowering weeds as source of food and shelter of natural enemies.
The highest harvest from organic ecosystem around 297.6 kg and the lowest from inorganic (279.2 kg.The result of research showed that the activities of natural enemies controlled insect pest success in the organic ecosystem improving number of harvest in the organic ecosystem.The highest number of harvest meaning natural enemies success reduce number of insect pest attacked the rice plant.

Conclusion
Conclusion of the research: 1) the higher number of herbivore insects in the inorganic rice ecosystem (H' = 1.71).The lowest result from organic ecosystem (H' = 1.68); 2) the highest rice harvest higher the organic ecosystem (297 kg) and the lowest in the inorganic (279.2 kg).

Figure 1 .
Figure 1.Rice harvest result from organic and inorganic ecosystem.

Table 1 .
Shannon-Wiener index diversity (H') of herbivorous insect from rice organic and inorganic ecosystem.