Judul: Inventarisasi Penyakit Tanaman Padi (Oryza sativa L.) di Kecamatan Lubuk Basung dan Tanjung Raya, Kabupaten Agam, Sumatra Barat
Abstrak: Tanaman padi merupakan salah satu komoditas pangan penting di dunia. Penurunan produksi padi di Indonesia dan khususnya Sumatra Barat disebabkan oleh beberapa faktor penyakit tanaman seperti cendawan, bakteri, virus, dan nematoda. Berbagai macam penyakit yang mengancam produksi komoditas tanaman pangan telah dilaporkan termasuk komoditas tanaman padi. Patogen dapat merusak bagian tertentu atau bahkan seluruh organ tanaman. Faktor lingkungan menjadi salah satu penyebab pemencaran penyakit pada tanaman padi. Tujuan dari penelitian ini mengamati dan melakukan penghitungan kejadian dan keparahan penyakit tanaman padi di Kecamatan Lubuk Basung dan Tanjung Raya, Kabupaten Agam, Sumatra Barat. Penelitian akan dilaksanakan dalam lima tahap yaitu wawancara petani, penentuan tanaman contoh, penghitungan insidensi dan keparahan penyakit, penghitungan produksi padi, serta analisis data. Penyakit tanaman padi yang ditemukan yaitu hawar daun bakteri (Xanthomonas oryzae pv oryzae), blas (Pyricularia oryzae), hawar daun pelepah (Rhizoctonia solani), pucuk putih (Aphelenchoides besseyi), bercak cokelat sempit (Cercospora oryzae), dan busuk bulir bakteri (Burkholderia glumae). Hasil penelitian menunjukkan bahwa seluruh lahan pengamatan ditemukan penyakit tanaman padi dengan lahan LB1, LB3, LB5, TR2, TR3, TR5 rata rata menunjukkan insidensi dan keparahan penyakit yang tinggi dibandingkan lahan pengamatan lainnya., Rice Plant is one of the most important food commodities in the world. The decline in rice production in Indonesia and especially West Sumatra is caused by several plant disease factors such as fungi, bacteria, viruses, and nematodes. Various diseases that threaten the production of food crop commodities have been reported, including rice commodities. Pathogens can damage certain parts or even entire plant organs. Environmental factors are one of the causes of the spread of disease in rice plants. The purpose of this study was to observe and calculate the incidence and severity of rice disease in Lubuk Basung and Tanjung Raya, Agam, West Sumatra. The research will be carried out in five stages, farmers interview, determining sample plants, calculating disease incidence and severity, calculating rice production, and analyzing data. Rice plant diseases found were bacterial leaf blight (Xanthomonas oryzae pv oryzae), blast (Pyricularia oryzae), sheath blight (Rhizoctonia solani), white tip (Aphelenchoides besseyi), narrow brown spot (Cercospora oryzae), and bacterial grain rot (Burkholderia glumae). The results showed that all of the observed rice plant diseases were found with LB1, LB3, LB5, TR2, TR3, TR5 fields on average showing a high incidence and severity of disease compared to other observation fields.
Keyword: dispersal, pathogen, rice production

Judul: National Rice Production and its Important Disease Intensity in Sukabumi District
Abstrak: Produksi beras sebagai sumber pangan pokok ditingkatkan untuk memenuhi kebutuhan masyarakat Indonesia yang jumlah penduduknya selalu meningkat. Produksi padi di Indonesia berfluktuasi karena berbagai faktor abiotik dan biotik, termasuk hama dan penyakit. Produksi beras nasional Indonesia meningkat selama periode 2011-2017, kemudian menurun secara signifikan pada 2018-2020. Penurunan produksi beras juga terjadi di lima provinsi penghasil beras terbesar yaitu Jawa Tengah, Jawa Timur, Jawa Barat, Sulawesi Selatan, dan Sumatera Selatan pada periode 2018-2021. Petani padi di Kecamatan Jampangkulon dan Cibitung Kabupaten Sukabumi menerapkan cara budidaya dan pengelolaan OPT secara konvensional, yaitu mengandalkan pupuk kimia dan pestisida sintetik. Penyakit penting yang ditemukan pada padi varietas lokal, Trisakti dan IR64 dari pengamatan lapangan di Kabupaten Sukabumi adalah bercak daun lonjong atau blas jamur oleh Pyricularia oryzae dan hawar daun bakteri oleh Xanthomonas oryzae pv. oryzae. Insidensi penyakit P. oryzae mencapai 100% pada ketiga varietas dengan tingkat severitas berkisar 60,7-66,7% pada daun dan 52,3-60% pada malai, sedangkan hawar bakteri menyebabkan insidensi 76,7-93,3% dan severitas 33,0- 64,4%. Varietas padi lokal paling tahan terhadap P. oryzae dibandingkan dua varietas lainnya, sedangkan Trisakti relatif lebih tahan penyakit hawar daun bakteri. Varietas IR64 paling rentan terhadap kedua penyakit tersebut dibandingkan dengan varietas lainnya. Berdasarkan analisis usahatani dan rasio keuntungan terhadap biaya (rasio B/C), varietas yang paling menguntungkan berturut-turut adalah lokal, IR64 dan Trisakti. Kata kunci: Rasio B/C, Xanthomonas oryzae pv. oryzae, Pyricularia oryzae, insidensi, severitas, fluktuasi produksi padi, Rice production as a staple food source is increased to meet the needs of the Indonesian people, whose population is always increasing. Rice production in Indonesia fluctuates due to various abiotic and biotic factors, including pests and diseases. Indonesia's national rice production increased during the 2011-2017 period, then decreased significantly in 2018-2020. The decline in rice production also occurred in the five largest rice producing provinces, namely Central Java, East Java, West Java, South Sulawesi and South Sumatra in the period 2018-2021. Rice farmers in Jampangkulon and Cibitung Subdistricts, Sukabumi Regency, apply conventional methods of cultivating and managing pests, which rely on chemical fertilizers and synthetic pesticides. The important diseases found in local rice varieties, Trisakti and IR64 from field observation in Sukabumi District were fungal oval leaf spot or blast by Pyricularia oryzae and bacterial leaf blight by Xanthomonas oryzae pv. oryzae. The incidence of disease by P. oryzae reached 100% in the three varieties with severity ranging from 60.7-66.7% on leaves and 52.3-60% on panicles, while bacterial blight caused incidence of 76.7-93.3% and severity 33.0-64.4%. The local rice variety was most resistant to P. oryzae than the other two varieties, while Trisakti was relatively most resistant to bacterial leaf blight. The IR64 variety was the most susceptible to both diseases compared to the other varieties. Based on the analysis of farming and benefit- cost ratio (B/C ratio), the most profitable varieties were local one, followed by IR64 and Trisakti, respectively. Keywords: B/C ratio, Xanthomonas oryzae pv. oryzae, Pyricularia oryzae, incidence, severity, rice production fluctuation
Keyword: B/C ratio, Xanthomonas oryzae pv. oryzae, Pyricularia oryzae, incidence, severity, rice production fluctuation

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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