Judul: Penyakit Busuk Buah Kopi (Colletotrichum sp.) terhadap Mutu dan Cita Rasa pada Kopi Arabika (Coffea arabica L.)
Abstrak: Kopi merupakan salah satu komoditas perkebunan yang memegang peranan penting di Indonesia, terutama dalam hal perekonomian. Penyakit busuk buah pada tanaman kopi telah menyebabkan kerugian yang besar bagi para petani kopi. Penyakit busuk buah menyebabkan kerugian serius telah dilaporkan pertama kali dari Kenya, sebesar 75% di beberapa perkebunan. Penyakit ini menyebabkan matinya tanaman kopi di beberapa daerah di Kenya dan Ethiopia. Di daerah lain, kerugian dapat mencapai 80%. Perkiraan konservatif lebih dari kerugian yang terjadi di Kenya adalah 20%. Gejala serangan penyakit busuk buah kopi dapat dilihat dari bercak hitam yang ada pada buah kopi. Hal ini menyebabkan buah kopi akan berubah warna menjadi hitam yang sebelumnya berwarna hijau. Jika buah kopi dibelah, maka seluruh dagingnya juga akan terlihat berwarna hitam. Kopi melalui berbagai rangkaian proses yang panjang mulai dari lahan hingga produk disajikan di dalam cangkir (from farm to cup). Setiap tahapan proses tersebut turut andil dalam cita rasa dan mutu produk yang dihasilkan. Produksi yang tinggi harus diikuti dengan kalitas dan citarasa yang baik, sehingga harga jual yang diperoleh petani atau perusahaan menjadi lebih tinggi. Penelitian ini bertujuan mengetahui penyakit busuk buah kopi (Colletotrichum sp.) terhadap mutu dan cita rasa pada kopi arabika (Coffea arabica L.). Pengamatan dilakukan pada empat petak perkebunan kopi. Tanaman contoh diamati sebanyak 20 tanaman di setiap petak, dengan metode pengambilan tanaman contoh secara diagonal. Pengamatan kejadian dan keparahan penyakit sebanyak empat kali dengan interval waktu satu minggu. Pengamatan busuk buah kopi diamati buah kopi yang terinfeksi. Wawancara dilakukan terhadap konsumen kopi. Wawancara berisi pertanyaan mengenai kesukaan terhadap rasa kopi. Data primer yang diperoleh dari pengamatan langsung di lapangan disajikan dalam Microsoft Excel 2013. Penyakit busuk buah kopi memberikan pengaruh terhadap mutu dan cita rasa kopi. Buah kopi yang terinfeksi Colletotrichum sp. menjadi cacat. Buah kopi yang terinfeksi dapat menghasilkan rasa pahit., Coffee is one of the plantation commodities that plays an important role in Indonesia, especially in terms of the economy. Coffee berry disease has caused great losses for coffee farmers. Coffee berry disease causing serious losses was first reported from Kenya, amounting to 75% on some plantations. This disease causes the death of coffee plants in some areas of Kenya and Ethiopia. In other areas, losses can be as high as 80%. A more conservative estimate of the losses incurred in Kenya is 20%. Symptoms of coffee berry disease can be seen from the black spots on the coffee cherries. This causes the coffee cherries to change color to black which was previously green. If the coffee cherries are split, the entire flesh will also look black. Coffee goes through a long series of processes starting from the farm to the product served in a cup (from farm to cup). Each stage of the process contributes to the taste and quality of the resulting product. High production must be followed by good quality and taste, so that the selling price obtained by farmers or companies becomes higher. The objective of this study is to observe the effect of coffee berry disease (Colletotrichum sp.) on the quality and taste in Arabica coffee (Coffea arabica L.).
Keyword: disease severity, pathogen, quality

Judul: Disease Incidence and Disease Severity of Coffee Leaf  Rust (Hemileia vastatrix) in Sangir District, South Solok Regency, West Sumatra  Province
Abstrak: Kopi merupakan salah satu komoditas perkebunan Indonesia yang banyak diproduksi dan diekspor. Salah satu penyakit penting yang menginfeksi tanaman kopi adalah penyakit karat daun kopi yang disebabkan oleh cendawan Hemileia vastatrix. Cendawan ini menginfeksi daun tanaman kopi sehingga fotosintesis tanaman dapat terganggu. Penelitian ini bertujuan mengetahui insidensi dan keparahan penyakit karat daun kopi pada tanaman kopi arabika di Kecamatan Sangir, Kabupaten Solok Selatan, Provinsi Sumatra Barat. Data mengenai penyakit, kondisi lahan, dan karakteristik petani, dikumpulkan dari 6 (enam) lahan pengamatan yang diberi nama: lahan A, B, C, D, E, dan F dengan cara menghitung skor insidensi dan skor keparahan penyakit serta wawancara petani. Sampel tanaman di masing-masing lahan (50 tanaman) dipilih menggunakan sistem diagonal. Data yang diperoleh ditabulasikan menggunakan aplikasi Microsoft Excel dan dianalisis dengan publikasi yang berasal dari buku, jurnal, dan buletin. Berdasarkan data yang telah diperoleh, pada minggu pertama pengamatan insidensi penyakit di lahan B, E, dan F sudah mencapai 100% sementara di lahan A, C, dan D masing-masing sebesar 40%, 88%, dan 52%. Insidensi penyakit pada minggu ke-5 pengamatan di lahan A, C, dan D masing- masing sebesar 78%, 90%, dan 78%. Persentase keparahan penyakit tertinggi pada minggu ke-5 pengamatan mencapai 72.89% pada lahan E sementara keparahan terendah mencapai 23.78% pada lahan A. Tidak ada pengendalian khusus yang dilakukan petani pada wilayah ini., Coffee is one of the Indonesia's plantation commodities which is widely produced and exported. One of the important diseases which is able to reduce the production is coffee leaf rust disease caused by the fungus Hemileia vastatrix. This fungus infects the leaves of the coffee plant so that the plant's photosynthesis can be disrupted. This study aims to determine the disease incidence and the disease severity of coffee leaf rust disease in arabica coffee plants in Sangir District, South Solok Regency, West Sumatera. Data of the disease, field condition, and farmers characteristics were collected from 6 observation plots which selected based on the possibility access, namely A, B, C, D, E, and F by calculating the disease incidence and disease severity scores and farmers interview. Sample plants in each plots (50 plants) were selected using diagonal system. Collected data were tabulated using the Microsoft Excel and be analyzed with published data from the books, journals, and newsletters. Based on the collected data, disease incidence at the 1st week on B, E, and F plots were already 100%, while on A, C, and D plots were up to 40, 88, and 52%, respectively. Disease incidence at the 5th week of observation on A, C, and D plots were up to 78, 90, and 78%, respectively. The highest percentage of disease severity at the 5th week of observation was up to 72.89% on E plot, while the lowest was up to 23.78% on A plot. There were no specific controls conducted by the farmers in this area.
Keyword: Coffeae arabica, C. robusta, Fungi, Integrated Pest Management

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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