Judul: Knowledge, Attitudes and Practices of Farmers in  the use of pesticides on Citrus Plantations in Simalungun Regency
Abstrak: Jeruk (Citrus spp.) merupakan tanaman tahunan yang tergolong kedalam famili Rutaceae. Serangan hama pada tanaman jeruk merupakan salah satu faktor penting yang harus diperhatikan untuk mempertahankan bahkan untuk meningkatkan hasil dengan kualitas dan kuantitas yang optimal. Penurunan produktivitas jeruk sering terjadi yang salah satunya diakibatkan oleh serangan organisme pengganggu tanaman (OPT). Pengendalian OPT baik hama maupun penyakit pada tanaman jeruk dilakukan oleh petani menggunakan pestisida. Penggunaan pestisida harus mengikuti rekomendasi yang telah ditentukan karena apabila tidak sesuai maka dapat menyebabkan berbagai dampak negatif. Penelitian ini bertujuan mempelajari pengetahuan, sikap dan tindakan petani dalam penggunaan pestisida untuk pengendalian OPT pada pertanaman jeruk di Kabupaten Simalungun, Sumatera Utara. Penelitian dilaksanakan pada bulan Mei hingga Agustus 2021 menggunakan metode survei langsung di lapangan dengan kuesioner terstruktur untuk mendapatkan data primer. Penentuan lokasi pengambilan contoh dilakukan secara terpilih (purposive) yang didasarkan pada populasi penduduk yang bekerja sebagai petani jeruk di tiga kecamatan yaitu Kecamatan Pematang Silimahuta, Purba, dan Silimakuta. Petani responden yang dipilih secara acak berjumlah 50 orang. Data yang diperoleh kemudian dianalisis secara deskriptif untuk mendeskripsikan tingkat pengetahuan, sikap dan tindakan petani dalam penggunaan pestisida. Secara umum petani responden memiliki pengetahuan, sikap dan tindakan yang cukup baik dalam penggunaan pestisida. Sebagian besar petani mengendalikan hama dan penyakit menggunakan pestisida sintetik dengan bahan aktif abamektin dan sipermetrin., Citrus (Citrus spp.) is an annual plant belonging to the Rutaceae family. Pest infestation on citrus plants is one of the important factors that must be considered in order to increase the high citrus production, both in quality and quantity. The decrease of citrus productivity often occurs due to plant pest and disease attacks. Generally farmers control the pests using synthetic pesticides. The use of synthetic pesticides is a common method used by farmers to control pests and diseases in citrus plants. The application of pesticides must follow the recommendations. However, the improper and exceesive uses of pesticides can cause various negative impacts, one of which is pesticide residues. This study aimed to study the knowledge, attitudes and practices of farmers in the use of pesticides in pest management of citrus plantations in Simalungun Regency, North Sumatra. The research was conducted from May to August 2021 using a direct survey method in the field using a structured questionnaire to obtain primary data. The respondents were selected using purposive sampling based on the population who worked as citrus farmers in the three selected sub-districts, namely Pematang Silimahuta, Purba, and Silimakuta sub-districts. The number of respondent farmers selected was 50 people. Data obtained were then descriptively analysis to describe the level of knowledge, attitudes, and practices of farmers in the use of pesticides. In general, respondents had good knowledge, attitudes and practices in the use of pesticides. Most farmers used synthetic pesticides with active ingredients of abamectin and cypermethrin in order to control the pests.
Keyword: negative impact, pesticide application, plant pests and diseases

Judul: Application of Pesticides in Pest and Disease Control and Harvest Product Management of Keprok Orange (Citrus reticulata L.) in Dau District, Malang Regency
Abstrak: Jeruk merupakan komoditas yang banyak digemari dan dikonsumsi oleh masyarakat di Indonesia. Jeruk keprok merupakan salah satu kultivar jeruk yang mudah dalam penanamannya, dapat tumbuh pada berbagai kondisi iklim dan dapat ditanam dimana saja, baik di dataran rendah maupun tinggi. Permasalahan yang sering dijumpai dalam setiap pertanaman yaitu adanya serangan hama dan penyakit. Penerapan sistem pengendalian OPT yang belum optimum menyebabkan penggunaan pestisida seringkali tidak tepat sasaran dan melebihi dosis anjuran sehingga berpengaruh pada keamanan konsumen buah jeruk. Penelitian ini bertujuan mengetahui pengetahuan, sikap, dan tindakan petani jeruk keprok dalam penggunaan pestisida, mengetahui hama dan penyakit utama, dan mengetahui tindakan yang dilakukan terhadap produk hasil panen. Penelitian dilakukan di Kecamatan Dau, Kabupaten Malang dengan metode survei langsung menggunakan kuisioner terstruktur. Responden ditentukan dengan menggunakan perpaduan metode purposive sampling dan snowball sampling. Sebanyak 50 petani responden (100%) menyatakan menggunakan pestisida sintetik untuk pertanaman jeruknya. Hama utama pada pertanaman jeruk keprok adalah lalat buah (Bactrocera spp.) (100%), kutu-kutuan (T. citricida, T. aurantii, A. gossypii) (92%), dan penyakit utama yaitu busuk pangkal batang yang disebabkan oleh P. nicotianae (86%). Pengetahuan, sikap, dan tindakan petani dalam penggunaan pestisida dipengaruhi oleh pengalaman bertani yang turun-temurun dan tingkat pendidikan. Jenis pestisida yang digunakan meliputi insektisida sistemik dan kontak, serta fungisida yang bersifat protektif. Organofosfat dan karbamat merupakan golongan pestisida yang paling banyak digunakan. Mayoritas responden (100%) langsung menjual hasil panennya yang menyebabkan kemungkinan adanya residu pada buah jeruk., Citrus is a perennial fruit plant that is consumed by many people of Indonesia. Keprok orange is one of the citrus cultivars that is easy to be cultivated, well grow in various climatic conditions and altitudes, either in the lowlands or in the highlands. Pests and diseases often cause the decrease of keprok orange quantitatively as well as qualitatively. The improper and exceed use of pesticides lead to negative effect citrus fruit consumers. This study aimed to determine the knowledge, attitudes, and practices in the application of pesticides, to determine the main pests and main diseases, and to determine the practice that taken on harvested products. The research was conducted in Dau District, Malang Regency through direct survey methods using structured questionnaires. Sampling of respondents used a combination of purposive sampling and snowball sampling methods. Based on the results of interviews, 50 respondent farmers (100%) used synthetic pesticides for their citrus plantations. The main pests of keprok orange plantations were fruit flies (Bactrocera spp.) (100%), aphids (Toxoptera citricida, T. aurantii, Aphis gossypii) (92%), and the main disease was stem rot caused by Phyrophthora nicotianae (86%). Farmer’s knowledge, attitudes, and practices in the use of pesticides are influenced by their experience and education level. The types of pesticides used include systemic and contact insecticides and protective fungicides. Organophosphates and carbamates are the most widely used pesticides. The majority of respondents (100%) directly sell their harvested products which led to the possibility of residue on citrus fruits.
Keyword: Keprok orange, Residues, Survey, Synthetic pesticide

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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