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: Disease Incidence and Severity of Blast (Pyricularia  oryzae) and Bacterial Leaf Blight (Xanthomonas oryzae pv. oryzae) on Rice  Plants in Gebang and Kuripan Villages, Pekalongan City, Central Java
Abstrak: Padi adalah sumber pangan penting bagi masyarakat di dunia terutama masyarakat Indonesia. Peningkatan produktivitas padi memiliki beberapa kendala seperti adanya penyakit tanaman. Terdapat dua penyakit penting padi di Indonesia yaitu blas (Pyricularia oryzae) dan hawar daun bakteri (Xanthomonas oryzae pv. oryzae). Penelitian ini bertujuan mengukur tingkat insidensi dan keparahan penyakit blas dan hawar daun bakteri pada tanaman padi di Kota Pekalongan, Jawa Tengah. Pengamatan di lapangan dilakukan pada 5 petak contoh di Desa Gebang dan 5 petak di Desa Kuripan. Pengamatan juga dilakukan terhadap bobot 1000 butir gabah kering panen dari tanaman contoh. Selain pengamatan di lapangan juga dilakukan wawancara dengan petani. Di Desa Gebang varietas yang ditanam adalah Varietas Inpari 43, sedangkan di Desa Kuripan ditanam varietas Inpari 42. Hasil penelitian menunjukkan bahwa serangan P. oryzae dan X. oryzae pv. oryzae ditemukan pada semua petak pengamatan. Keparahan penyakit blas pada lahan pengamatan di Desa Gebang relatif lebih tinggi (rata-rata 51.11%) dibandingkan dengan lahan pengamatan di Desa Kuripan (rata-rata 25.55%). Keparahan penyakit HDB pada lahan Desa Gebang juga relatif lebih tinggi (rata- rata 92%) dibandingkan dengan lahan pengamatan di Desa Kuripan (rata-rata 60.44%), Rice is an important crops as staple food in Indonesia. Increasing rice productivity has an important constraint such as plant diseases. Two important rice diseases in Indonesia are blast (Pyricularia oryzae) and bacterial leaf blight (Xanthomonas oryzae pv. oryzae). This study was aimed to measure the incidence and severity of blast and bacterial leaf blight diseases on rice plants in Pekalongan City, Central Java. As many as 5 sample plots of rice fields each in Gebang Village and Kuripan Village were observed. Observations were also carried out on the weight of 1000 dry-harvested grains from the sample plants. In Gebang plots were grown Inpari 43 variety, while in Kuripan plots were grown Inpari 42 variety. This study has shown that blast and bacterial leaf blight disease were observed in all observation plots. The severity of blast disease in the observation plots in Gebang Village was relatively higher (51.11%) than Kuripan Village (25.55%). Similarly BLB disease severity in Gebang Village was higher (92%) than in Kuripan Village (60.44%)
Keyword: Grain, Inpari 42, Inpari 43, Plots, 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.
Keyword: