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: Keefektifan Minyak Serai Wangi dan Minyak Cengkih terhadap Busuk Buah Kakao (Phytophthora palmivora Butl.)
Abstrak: Phytophthora palmivora merupakan patogen yang sering menginfeksi buah kakao dan menyebabkan kerugian pada pertanaman. Pengendalian yang biasa dilakukan adalah dengan menggunakan pestisida sintetik yang dapat menyebabkan dampak negatif pada lingkungan. Oleh karena itu diperlukan pestisida ramah lingkungan sebagai salah satu alternatif pengendalian. Minyak atsiri memiliki kelebihan yaitu tidak berdampak negatif pada lingkungan sehingga dapat dimanfaatkan sebagai salah satu alternatif pengendalian penyakit busuk buah kakao. Minyak atsiri yang berpotensi digunakan sebagai fungisida nabati diantaranya adalah minyak serai wangi dan cengkih. Tujuan studi pustaka ini sebagai informasi mengenai keefektifan minyak serai wangi dan minyak cengkih sebagai fungisida nabati dalam mengendalikan P. palmivora penyebab busuk buah kakao. Studi pustaka yang dilakukan dengan mengumpulkan berbagai data dan informasi dari beberapa literatur yang meneliti mengenai keefektifan minyak serai wangi dan minyak cengkih dalam mengendalikan penyakit busuk buah kakao, potensi serta kandungan minyak serai wangi dan minyak cengkih sebagai fungisida nabati. Data yang diperoleh dari berbagai pustaka meliputi data uji in vitro dan in vivo untuk dirangkum dan ditabulasi. Hasil yang diperoleh menunjukkan bahwa minyak serai wangi dan minyak serai mampu menghambat pertumbuhan P. palmivora secara in vitro maupun in vivo dengan faktor yang memengaruhi keefektifannya., Black pod disease caused by Phytophthora palmivora is a common disease that infected cacao’s pod that decrease the production of cacao planting. Common control strategy of cacao disease is by using synthetic pesticide which have negative impact to the environment, hence we need environmentally friendly pesticide as an alternative control. The essential oil have no negative effect for the environment, thus can be considered as alternative control of black pod disease. Citronella and clove oils have potential to serve as biological fungicide. The aim of the literature review to provide information regarding the effectiveness of citronella and clove oils as an inhibitor to P. palmivora as black pod pathogen. The information collected from literature which is discuss about effectiveness of citronella and clove oils as an inhibitor P. palmivora, potential and composition of citronella and clove oils as biological fungicide. The data collected from literature that include in vitro and in vivo tests prosessed to tabulation and summary for better understanding. The conclusion of this study give information that citronella and clove oils can inhibit growth of P. palmivora by in vitro and in vivo test with factors that affect the effectiveness.
Keyword: fungisida nabati, in vitro, in vivo, minyak atsiri.

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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