Judul: Phenotypic and molecular characterizations of bacterial pathogen and epidemy of bacterial leaf blight on Acacia crassicarpa seedlings
Abstrak: Bacterial leaf blight (BLB) disease is a new and deadly disease on Acacia crassicarpa nursery in Pelelewan Riau and never been reported either in Indonesia or in other countries. This research was designed to study etiology of BLB disease on A. crassicarpa seedlings and other factors that triggered epidemy of BLB disease. The result showed that the first symptom of BLB appeared on 5-6 weeks-old seedlings and blight was formed within 1-2 weeks., Bacterial leaf blight (BLB) disease is a new and deadly disease on Acacia crassicarpa nursery in Pelelewan Riau and never been reported either in Indonesia or in other countries. This research was designed to study etiology of BLB disease on A. crassicarpa seedlings and other factors that triggered epidemy of BLB disease. The result showed that the first symptom of BLB appeared on 5-6 weeks-old seedlings and blight was formed within 1-2 weeks.
Keyword: molecular identification, epidemy of BLB, Xanthomonas campestris, disease symptom, Riau

Judul: Inventory Disease on Acacia crassicarpa Cunn Ex Benth at Kerinci Central Nursery 1 and Pelalawan Estate PT RAPP Pelalawan District Riau
Abstrak: Acacia crassicarpa merupakan salah satu tanaman berkayu yang digunakan untuk pembuatan pulp dan kertas. Hutan tanaman industri (HTI) PT. Riau Andalan Pulp and Paper (RAPP) merupakan salah satu HTI yang membudidayakan tanaman A. crassicarpa. A. crassicarpa dibudidayakan secara monokoltur dan tumbuh baik meskipun di lahan kritis. Penyakit tanaman merupakan salah satu masalah penting di perkebunan Akasia. Infeksi patogen dapat menyebabkan gangguan fisiologis yang mempengaruhi pertumbuhan tanaman dan kualitas kayu. Penelitian ini bertujuan untuk mengamati dan mengidentifikasi patogen yang menginfeksi A. crassicarpa di PT. RAPP. Pengamatan penyakit dilakukan di empat lahan selama 4 bulan, dimulai dari Januari sampai Mei 2022 di Kebun Pelalawan dan Sentral Pembibitan 1 PT RAPP Pangkalan Kerinci, Kabupaten Pelalawan, Provinsi Riau. Pengambilan sampel menggunakan metode purposive sampling. Tahap identifikasi penyakit dilakukan di laboratorium PT RAPP. Patogen penyebab diidentifikasi berdasarkan gejala visual dan bentuk mikroskopisnya. Penyakit bibit A. crassicarpa adalah layu daun yang disebabkan oleh Rhizoctonia sp., sedangkan penyakit pada tanaman adalah bercak daun yang disebabkan oleh Pestalotiopsis sp. dan Passalora perplexa, serta hawar daun yang disebabkan oleh Xanthomonas campestris pv. acaciae. Faktor yang mempengaruhi infeksi patogen di lapangan antara lain curah hujan, suhu, dan kelembaban., Acacia crassicarpa is a woody plant used for pulp and paper production. Industrial plantation forest (HTI) PT. Riau Andalan Pulp and Paper (RAPP) is one of the HTI plantations that cultivates A. crassicarpa plants. A. crassicarpa is cultivated in monoculture and grows well even on critical land. Plant disease is one of the important problems in Acacia plantations. Pathogenic infections can cause physiological disturbances that affect plant growth and wood quality. This study aims to observe and identify the pathogens that infect A. crassicarpa in PT. RAPP. Disease observations were carried out in four fields for 4 months, starting from January to May 2022 at the Pelalawan Garden and Central Nursery 1 PT RAPP Pangkalan Kerinci, Pelalawan Regency, Riau Province. Sampling using purposive sampling method. The disease identification proses was conducted at PT RAPP laboratory. The causative pathogen is identified based on its visual symptoms and microscopic appearance. Seedling disease of A. crassicarpa is leaf wilt caused by Rhizoctonia sp., while plant diseases were leaf spot caused by Pestalotiopsis sp. and Passalora perplexa, and leaf blight caused by Xanthomonas campestris pv. acaciae. Factors that affect disease infections in the field include rainfall, temperature, and humidity.
Keyword: Acacia crassicarpa, hutan tanaman industri, patogen, penyakit

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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