Judul: Incidence and Severity of Blast (Pyricularia oryzae) Disease in Sukajati Village, Haurgeulis District, Indramayu Regency, West Java
Abstrak: Padi (Oryza sativa) sebagai makanan pokok terus diproduksi di Indonesia. Namun penyakit tanaman seringkali menjadi kendala utama dalam budidaya padi. Pyricularia oryzae merupakan penyebab utama penyakit padi, yang dilaporkan menurunkan produksi padi di berbagai daerah. Patogen ini menginfeksi 1.285 juta hektar atau sekitar 12% dari total luas areal persawahan di Indonesia. Penelitian ini bertujuan untuk mengetahui insidensi dan keparahan penyakit blas pada persawahan di Desa Sukajati, Kecamatan Haurgeulis, Kabupaten Indramayu, Jawa Barat selama bulan Juni sampai Juli 2020. Metode yang dilakukan dalam penelitian ini adalah: (1) wawancara dengan petani, (2) pengumpulan data di lapangan dengan penentuan plot pada 5 sampel sawah berdasarkan budidaya padi, yaitu Mekongga 3 petak dan Ciherang 2 petak, (3) pengukuran insidensi dan keparahan penyakit, dan (4) analisis data. Rata-rata insidensi penyakit dan tingkat keparahan penyakit pada 8 minggu setelah tanam relatif lebih tinggi pada kultivar Mekongga dibandingkan dengan kultivar Ciherang. Insidensi penyakit di Mekongga dan Ciherang masing-masing mencapai 66.7% dan 20.0%, dan tingkat keparahan penyakit pada kedua kultivar tersebut masing-masing mencapai 18.7% dan 4.0%., Rice (Oryza sativa) as the staple food is produced continuously in Indonesia. However, plant diseases often become on of the main constrains in rice cultivation. Pyricularia oryzae on of the main rice disease causal agents, was reported to decrease rice production in many areas. This pathogen infects 1.285 million hectares or around 12% of the total area of rice cultivation in Indonesia. This study was aimed to observe the incidence and severity of blast disease in rice fields in Sukajati Village, Haurgeulis District, Indramayu Regency, West Java during June to July 2020. The methods conducted in this study were: (1) famers interview, (2) data collection in the field by determination of plots in 5 rice field samples based on the rice cultivar, i.e. Mekongga (3 plots) and Ciherang (2 plots), (3) measurement of disease incidence and severity, and (4) data analysis. The average of disease incidence and disease severity on 8week after transplanting was relatively higher on Mekongga cultivar compared to Ciherang cultivar. Disease incidence on Mekongga and Ciherang was up to 66.7% and 20.0%, respectively, and disease severity on those two cultivar was up to 18.7% and 4.0%, respectively
Keyword: Ciherang cultivar, Mekongga cultivar, Rice diseases

Judul: National Rice Production and Bacterial Leaf Blight Disease in District of Indramayu, West Java
Abstrak: Padi (Oryza sativa) merupakan tanaman pangan penting di berbagai negara di dunia termasuk Indonesia. Produksi padi Indonesia mengalami fluktuasi yang dipengaruhi oleh berbagai faktor seperti alih fungsi lahan, agro-klimat, dan organisme pengganggu tanaman. Salah satu penyakit penting padi adalah hawar daun bakteri (HDB) oleh Xanthomonas oryzae pv. oryzae. Upaya pengendalian penyakit tersebut antara lain penggunaan varietas tahan, kultur teknis, hayati dan kimiawi. Penelitian ini bertujuan menggambarkan produksi padi secara nasional dan intensitas penyakit HDB pada tanaman padi di Kabupaten Indramayu, Jawa Barat. Data produksi padi tingkat nasional, provinsi dan kabupaten diakses secara daring dari website Badan Pusat Statistik, kegiatan lapangan meliputi pengumpulan data usaha tani dan produksi padi melalui wawancara dengan petani, pengamatan gejala dan intensitas penyakit di petak sawah contoh milik petani. Produksi padi nasional pada periode tahun 2011-2021 menunjukkan peningkatan selama tujuh tahun pertama, kemudian menurun dalam tiga tahun terakhir secara nyata. Pada periode waktu yang sama Provinsi Jawa Barat sebagai produsen padi nasional terbesar ketiga juga menunjukkan penurunan produksi. Indramayu merupakan kabupaten penghasil padi utama di Jawa Barat juga memiliki produksi yang berfluktuasi yang dipengaruhi produksi tahunan di kecamatan-kecamatan utama. Penyakit HDB di lahan pengamatan contoh Kabupaten Indramayu menunjukkan intensitas beragam antar varietas padi. Insidensi penyakit pada padi varietas Ciherang adalah 79,4% yang lebih rendah daripada Mekongga (83%) dan varietas Kebo Putih (92%). Sementara itu, severitas penyakit dari yang terendah adalah varietas Ciherang, local dan Mekongga berturut-turut 24,07, 35,11 dan 83%. Varietas Ciherang memiliki tingkat ketahanan terhadap HDB lebih baik daripada dua varietas lainnya., Rice (Oryza sativa) is an important food crop in various countries in the world, including Indonesia. Indonesian rice production fluctuates, which is influenced by various factors such as land conversion, agro-climate, and plant pest organisms. One of the important diseases of rice is bacterial leaf blight (BLB) by Xanthomonas oryzae pv. oryzae. Efforts to manage the disease include the use of resistant varieties, technical, biological and chemical control techniques. This study aims to describe the national rice production and the intensity of HDB disease in rice plants in Indramayu Regency, West Java. Data on rice production at the national, provincial and district levels is accessed online from the website of the Central Statistics Agency (BPS), field activities include collecting data on farming and rice production through interviews with farmers, observing symptoms and intensity of disease in sample rice fields belonging to farmers. National rice production in the 2011-2021 period showed an increase for the first seven years, then decreased significantly in the last three years. In the same period of time, West Java Province as the third largest national rice producer also showed a decline in production. Indramayu is the main rice producing district in West Java and also has fluctuating production which is influenced by annual production in the main sub-districts. BLB disease in the sample observation area of Indramayu District showed varying intensity between rice varieties. The incidence of disease in Ciherang rice varieties was 79.4% which was lower than Mekongga (83%) and Kebo Putih varieties (92%). Meanwhile, the disease severity from the lowest was ‘Ciherang’, ‘local’ and Mekongga varieties, respectively 24.07, 35.11
Keyword: Disease incidence, disease severity, production fluctuation, variety resistence, Xanthomonas oryzae pv, oryzae

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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