Judul: Intensity of Leaf Blight Disease on Trembesi (Samanea saman (Jacq.) Merr.) in the Nursery of PT Indominco Mandiri
Abstrak: Kegiatan pertambangan harus melakukan reklamasi untuk memulihkan kerusakan akibat kerusakan lingkungan. Reklamasi memerlukan bibit bermutu baik, yang diperoleh di persemaian. Bibit di persemaian sering menghadapi masalah yaitu munculnya penyakit pada bibit. Oleh karena itu diperlukan tindakan pencegahan dan pengendalian yang tepat. Penelitian ini bertujuan untuk mengetahui intensitas serangan penyebab penyakit hawar daun pada semai trembesi di persemaian PT Indominco Mandiri. Metode penelitian meliputi survei penyakit hawar daun pada bibit trembesi berumur 4, 8, dan 10 bulan dengan menggunakan metode sampling diagonal dengan intensitas sampling 10% untuk mengamati kejadian dan intensitas penyakit. Sampel daun yang bergejala hawar daun diambil untuk diisolasi untuk mengetahui penyebab penyakitnya, kemudian dilakukan uji patogenisitas. Kejadian dan intensitas penyakit tertinggi yaitu pada petak 1 sebesar 71,00% dan 37,67%. Intensitas penyakit termasuk kedalam kategori rusak sedang (RS). Tidak ada perbedaan yang nyata dalam kejadian dan intensitas penyakit hawar daun antara petak-petak yang berbeda di persemaian. Uji patogenisitas menunjukkan semua isolat menyebabkan gejala penyakit dengan masa inkubasi 2-4 hari. Cendawan penyebab patogen hawar daun yang diisolasi dari daun trembesi mempunyai karakteristik seperti cendawan Diaporthe sp. Sa-1, Rhizoctonia sp. Sa-2, Cercospora sp. Sa-3, dan Colletotrichum sp. Sa-4., Mining activities must carry out reclamation to restore damage caused by environmental damage. Reclamation requires good quality seeds, which are obtained in nurseries. Germination in nurseries often faces obstacles, namely the emergence of diseases in seedlings. Therefore, appropriate preventive and control measures are needed. This study aims to determine the intensity of attacks that cause leaf blight disease on trembesi seedlings in PT Indominco Mandiri nursery. The research method includes a survey of leaf blight disease on trembesi seedlings aged 4, 8, and 10 months using the diagonal sampling method with sampling intensity of 10% to observe the incidence and intensity of the disease. Infected leaves were isolated to identify pathogens. The highest disease incidence (71,00%) and intensity (37.67%) were found in plot 1. The intensity of the disease is categorized as moderate damage (MD). There was no significant difference in the incidence and intensity of leaf blight disease between different plots in the nursery. The pathogenicity test showed that all isolates caused disease symptoms with an incubation period of 2-4 days. The fungi causing leaf spot disease isolated from trembesi leaves have characteristics such as Diaporthe sp. Sa-1, Rhizoctonia sp. Sa-2, Cercospora sp. Sa-3, and Colletotrichum sp. Sa-4.
Keyword: uji patogenisitas, hawar daun, trembesi, masa inkubasi

Judul: Identification and Pathogenicity Test of the Causes of Leaf Blight Disease in Teak at PT. Solusi Bangun Indonesia Nursery
Abstrak: Jati (Tectona grandis Linn) merupakan tanaman dari famili Verbenaceae yang digunakan sebagai tanaman revegetasi karena adaptif pada lahan kritis, tahan terhadap penyakit dan bernilai ekonomi tinggi. Permasalahan penyakit jati banyak terjadi di persemaian. Penelitian ini bertujuan untuk mengidentifikasi patogen penyebab penyakit hawar daun di Persemaian PT. SBI. Metode penelitian dilakukan dengan sensus di lapangan dan uji postulat Koch. Ditemukan hawar daun dengan luas serangan sebesar 93%, dengan ciri nekrosis. Empat isolat yang diberi kode S1, S2, S3, dan S4 didapatkan dengan uji postulat Koch. Hasil identifikasi cendawan menunjukkan bahwa isolat S1 dan S2 adalah Rhizoctonia sp. dengan ciri karakteristik hifa bersekat, sudut percabangan 90°, miselia sterilia dan memiliki struktur moniloid. Isolat S3 dan S4 adalah Curvularia sp. dengan ciri keberadaan hifa yang bersepta dan konidia yang terdiri atas 4-5 sel membentuk rantai., Teak (Tectona grandis Linn) is a plant from the Verbenaceae family used for revegetation due to its adaptability to critical lands, disease resistance, and high economic value. Problems with teak diseases frequently occur in nurseries. This study aims to identify the pathogens causing leaf blight disease in the nurseries of PT. SBI. The research methods included field surveys and Koch's postulates tests. Leaf blight with an attack rate of 93% was found, characterized by necrosis. Four isolates, coded S1, S2, S3, and S4, were obtained through Koch's postulates tests. Fungal identification results showed that isolates S1 and S2 were Rhizoctonia sp., characterized by septate hyphae, 90° branching angles, sterile mycelia, and monilioid structures. Isolates S3 and S4 were Curvularia sp., characterized by septate hyphae and conidia consisting of 4-5 cells forming chains.
Keyword: Agaricomycetes, Dothideomycetes, postulat Koch, patogenesitas, nekrosis

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: