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: 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: 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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