Judul: Pengendalian Penyakit Phytophthora dengan Fungisida Asam Fosfit pada Tanaman Kakao melalui Metode Injeksi Batang, Penyemprotan Kulit Batang, dan Irigasi Tetes
Abstrak: Cocoa production has been declining due to factors such as plant age, poor planting materials, and high pest and disease attacks. Phytophthora palmivora Butl. is a hemibiotrophic phytopathogen that may infect a wide variety of hosts, including many agricultural crops across the globe. Phytophthora palmivora causes two types of disease in cocoa trees: pod rot and stem canker resulted in the reduction of the quality and quantity of cocoa beans, with losses up to 30%. This research was aimed to determine the effective and economically viable disease management through phosphonic application. This study was conducted on a 5-year-old cocoa plantation in South Sulawesi, Indonesia, using a trunk injection method, stem bark spray, and drip irrigation. All treatments resulted in a substantial reduction in lesion size and sporulation on inoculated sample with differing levels of effectiveness. Considering its effectiveness in suppressing Phytophthora disease development, 80 ml and 40 ml-injected tree and 40 ml-sprayed tree of phosphonic acid showed the best results. Although higher doses (80 ml/tree) provide better control of stem canker, the use of the lowest dose (20 ml/tree) was adequate to suppress lesion development, particularly in the injection method. While the economical analysis on 1 ha cocoa field showed that injection of 80 ml/tree and drip irrigation of 40 ml/tree produced the highest income per season of IDR 136 and 132 million., Produksi kakao terus mengalami penurunan signifikan yang diakibatkan oleh beberapa faktor seperti umur tanaman, bahan tanam yang rentan, dan tingginya serangan hama dan penyakit. Phytophthora palmivora Butl. merupakan cendawan hemibiotrofik yang dapat menginfeksi berbagai macam inang yang tersebar di seluruh dunia, termasuk kakao. Phytophthora palmivora menyebabkan dua jenis penyakit pada tanaman kakao yaitu penyakit busuk buah dan kanker batang yang mengakibatkan penurunan kualitas dan kuantitas biji kakao, dengan kerugian mencapai 30%. Penelitian ini bertujuan menentukan pengendalian penyakit yang efektif dan ekonomis melalui aplikasi asam fosfit. Penelitian ini dilakukan pada perkebunan kakao berumur 5 tahun di Sulawesi Selatan, Indonesia, dengan menggunakan metode injeksi batang, penyemprotan kulit batang, dan irigasi tetes. Berdasarkan hasil, aplikasi asam fosfit menunjukkan penurunan substansial dalam diameter lesi dan sporulasi pada sampel yang diinokulasi dengan tingkat efektivitas yang berbeda. Hasil pengamatan menunjukkan bahwa injeksi asam fosfit dengan dosis 80 dan 40 ml/pohon, penyemprotan pada dosis 40 ml/pohon, dan melalui irigasi tetes 40 ml/pohon merupakan hasil terbaik dalam menekan perkembangan penyakit phytophthora. Meskipun demikian, penggunaan dosis terendah (20 ml/pohon) telah mampu menekan perkembangan penyakit kanker batang, terutama pada metode injeksi. Sementara itu, analisis ekonomi pada lahan kakao seluas 1 ha menunjukkan bahwa injeksi 80 ml/pohon dan drip irrigation 40 ml/pohon menghasilkan pendapatan per musim tertinggi yaitu 136 dan 132 juta rupiah.
Keyword: cocoa pod rot, phosphonic acid, Phytophthora palmivora, stem canker

Judul: Black Pod Rot Disease (Phytophthora palmivora Butl.) Control Management on Cocoa (Theobroma cacao L.) at Jatirono Plantation, PT Perkebunan Nusantara XII (Persero), Banyuwangi, East Java
Abstrak: Kegiatan magang bertujuan mempelajari budidaya tanaman kakao baik secara teknis maupun manajerial. Kegiatan magang juga bertujuan mempelajari manajemen pengendalian Phytophthora palmivora secara kultur teknis, manual, dan kimiawi. Magang dilaksanakan di Kebun Jatirono, PT Perkebunan Nusantara XII, Banyuwangi, Jawa Timur yang berlangsung dari bulan Januari 2020 hingga April 2020. Pengendalian P. pamivora secara kultur teknis dilakukan melalui pemangkasan dan pemupukan. Hasil analisis menunjukkan areal kakao yang memiliki kelembaban rendah memiliki tingkat serangan P. palmivora yang lebih rendah jika dibandingkan dengan areal dengan kelembaban tinggi. Pengendalian P. palmivora secara mekanis dilakukan dengan kegiatan membuang buah busuk (B3) yaitu menurunkan buah yang terserang P. palmivora. Jumlah buah yang diturunkan kemudian dikonversi menggunakan pod index di Afdeling Sumber Baru yaitu sebesar 33 yang menandakan setiap kehilangan 33 buah berarti telah terjadi kehilangan hasil sebanyak 1 kg. Pengendalian secara kimiawi dilakukan menggunakan fungisida berbahan aktif mankozeb dengan konsentrasi 0.83 g l-1 dan fosfonat dengan konsentrasi 20 ml l-1 ., tion. In addition, the aim of the internships was to study the management control of Phytophthora palmivora on cocoa in technically, manually, and chemically. The internships conducted at Jatirono Plantations, PT Perkebunan Nusantara XII (Persero), Banyuwangi, East Java, from January to April 2020. P. palmivora control in technical culture is pruning,and fertilizing. Analysis results shows that areas of cocoa that had low humidity had a low attack rate of P. palmivora when compared with areas that had high humidity. P. palmivora control manually is doing by dispose a rot pod. The amount of reduced pod then converted with pod index in Jatirono Plantations is 33 which means that every loss of 33 pod means that has been loss of 1 kilograms of cocoa beans. Chemical control is doing by fungicide that contains active material mancozeb with 0.83 g l- 1 consentrations and phosphonate with 20 ml l-1 consentrations
Keyword: cocoa, manually, cultural technic, chemical, Phytophthora palmivora

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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