Judul: Inventory of Parasitic Nematodes of Chrysanthemum  Plants in the Kebun Mandiri Florist, Cidahu District, Bogor Regency, West Java
Abstrak: Krisan (Chrysanthemum spp.) merupakan komoditas florikultura dengan produksi dan volume ekspor tertinggi dari tanaman hias lainnya di Indonesia. Hama dan penyakit tanaman menjadi faktor penghambat utama dalam budidaya krisan, salah satunya adalah nematoda parasit (fitonematoda). Penelitian bertujuan menginventarisasi dan mengidentifikasi fitonematoda yang berasosiasi dengan tanaman krisan di Kebun Mandiri Florist. Pengambilan sampel tanah dan akar dilakukan pada umur 13, 15, dan 16 MST (minggu setelah tanam). Nematoda diekstraksi dari sampel tanah dengan metode flotasi-sentrifugasi dan sampel akar dengan metode pengabutan (mist chamber). Identifikasi morfologi nematoda berdasarkan pada karakteristik anterior (bentuk mulut dan stilet), posterior (bentuk ekor dan organ reproduksi), serta anulasi tubuh nematoda. Pengukuran karakter morfometrik dilakukan mengacu pada formula J G De Man. Data morfometrik nematoda ditabulasikan dengan Microsoft Excel 2019. Empat genus yang diidentifikasi, yaitu Pratylenchus, Rotylenchulus, Tylenchus, dan Coslenchus. Fitonematoda yang dominan pada krisan adalah Pratylenchus dengan populasi absolut mencapai 9737,78/4 g akar dan frekuensi absolut 100% pada semua umur dan derajat kesehatan tanaman., Chrysanthemum (Chrysanthemum spp.) is the flower with the highest production and export volume compared to other types of flowers in Indonesia. Pests and diseases are the causes of sub-optimal flower production, one of which is plant parasitic nematodes. The research aimed to make an inventory and identify plant-parasitic nematodes associated with chrysanthemum plants in Kebun Mandiri Florist. Soil and root samples were collected at 13, 15, and 16 WAP (weeks after planting). Nematodes were extracted from soil samples using the flotation centrifugation method, and from root samples using the mist chamber method. The morphological identification of nematodes was based on anterior characteristics (mouth and stylet shape), posterior characteristics (tail shape and reproductive organs), and body annulation. Measurements of morphometric characters were carried out in reference to the J G De Man formula. Nematode morphometric data was tabulated with Microsoft Excel 2019. Four genera were identified: that are Pratylenchus, Rotylenchulus, Tylenchus, and Coslenchus. The dominant phytomatode in chrysanthemums was Pratylenchus with an absolute population reaching 9737,78/4 g of roots and an abolute frequency of 100% at all ages and degrees of plant health.
Keyword: frekuensi absolut, morfologi, morfometri, absolute frequency, morphology, morphometry

Judul: Penyakit Pada Tanaman Krisan (Chrysanthemum morifolium) di PT Natalia Nursery Bogor
Abstrak: Krisan merupakan tanaman hias yang banyak diminati karena keindahannya. Penurunan produksi bunga krisan di Indonesia, khususnya di Jawa Barat, disebabkan oleh beberapa faktor termasuk patogen. Penelitian ini bertujuan untuk mendapatkan informasi mengenai intensitas penyakit dan mengidentifikasi patogen yang menginfeksi tanaman krisan di PT Natalia Nursery Bogor. Pengamatan meliputi jenis gejala, insidensi penyakit dan tingkat keparahan, serta hasil produksi. Pengamatan dilakukan setiap minggu selama lima kali pada tiga petak tanaman yang berbeda. Identifikasi patogen penyebab dilakukan dengan pengamatan mikroskopis dan dikonfirmasi dengan studi literatur. Berdasarkan hasil penelitian, ada lima penyakit yang ditemukan yaitu karat putih (Puccinia horiana), layu fusarium (Fusarium oxysporum), bercak daun (Septoria sp.), diduga virus/viroid dan nematoda puru akar (Meloidogyne spp.). Secara umum, insidensi dan keparahan penyakit mengalami peningkatan setiap minggunya. P. horiana adalah patogen dominan yang menginfeksi tanaman krisan dengan tingkat keparahan penyakit hingga 40,81% pada varietas rentan. Varietas krisan yang paling tahan terhadap infeksi patogen adalah Puspita Nusantara. Terdapat adanya korelasi antara insidensi dan keparahan penyakit karat putih dengan hasil produksi bunga krisan., Chrysanthemum is a highly demanded ornamental plant due to its beauty. The reduction of chrysanthemum production in Indonesia, especially in West Java, might be caused by several factors including pathogen infections. The field investigation aimed to obtain the disease intensity and to identify the pathogen infecting chrysanthemum plants at PT Natalia Nursery Bogor. The type of symptoms, disease incidence and severity, as well as yield were measured. The observations were conducted every week for five times at three different plots. Identification of the causal pathogens were carried out by microscopic observation and confirmed by literature studies. Five diseases were found, namely white rust (Puccinia horiana), fusarium wilt (Fusarium oxysporum), leaf spot (Septoria sp.), suspected virus/viroid, and root-knot nematode (Meloidogyne spp.). The disease incidence and severity was increasing every week. The P. horiana was the dominant pathogen infecting chrysanthemum in the nursery with disease severity up to 40,81%. The most susceptible chrysanthemum variety against pathogen infection was Puspita Nusantara. The disease incidence and severity white rust can affect the yield of chrysanthemum flowers.
Keyword: chrysanthemum, pest, incidence, severity

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: