Judul: Plant Parasitic Nematodes on Rice (Oryza sativa L.) in Medan Selayang District, Medan City, North Sumatra
Abstrak: Medan Selayang is one of the districts in Medan City, North Sumatra, and one of the rice production centers in Medan City. One of the problems faced regarding rice cultivation in Medan Selayang is disease caused by plant parasitic nematodes. Monitoring the presence of plant parasitic nematodes must be carried out to determine plant disease control strategies. This research examines a genus of plant parasitic nematodes on rice in Medan Selayang District, Medan City, North Sumatra. The research was carried out from January to March 2023 and carried out in seven stages: Survey and collecting samples from a rice field that exhibits symptoms of nematode infection. Extraction of parasitic nematodes in soil samples using the flotation-centrifugation method. Extraction of parasitic nematodes in root samples using the mist chamber method. Counting the number of parasitic nematodes. Making semi-permanent parasitic nematode preparations. Identifying the morphology of parasitic nematodes. Plant parasitic nematodes community analysis. Six genera of plant parasitic nematodes were identified from soil and root samples: Meloidogyne, Hirschmanniella, Tylenchus, Helicotylenchus, Criconemoides, and Criconemella. The dominant plant parasitic nematodes in the soil samples were Helicotylenchus (6.6/100 g of soil), while Meloidogyne dominated the roots (25/5 g of roots).
Keyword: Helicotylenchus, Meloidogyne, morphology identifications, nematodes

Judul: INVENTORY OF NEMATODES ON STRAWBERRY IN THREE PRODUCTION CENTERS, WEST JAVA
Abstrak: Stroberi (Fragaria L.) merupakan salah satu komoditas hortikultura bernilai ekonomi tinggi di Indonesia. Salah satu kendala budi daya stroberi adalah nematoda parasit tanaman stroberi (fitonematoda). Penelitian ini bertujuan mengidentifikasi genus nematoda dan menghitung populasi nematoda pada tiga sentra produksi stroberi di Jawa Barat. Sampel tanah, akar, dan daun diambil secara purposif dengan kriteria tanaman sehat dan tanaman bergejala penyakit. Nematoda diekstraksi dari tanah dengan metode flotasi sentrifugasi, sampel akar dengan mist chamber, dan sampel daun dengan perendaman dalam air. Nematoda diidentifikasi secara morfologi. Analisis komunitas nematoda dilakukan dengan menghitung indeks keanekaragaman Shannon-Wiener, indeks kemerataan, indeks dominansi, maturity index (MI), plant parasite index (PPI). Fitonematoda yang diidentifikasi, yaitu Aphelenchoides, Criconemella, Helicotylenchus, Hemicycliophora, Meloidogyne, Paralongidorus, Pratylenchus, Rotylenchulus, Rotylenchus, Scutellonema, Tylenchus, dan Xiphinema. Nematoda bukan parasit tanaman yang diidentifikasi, yaitu Alaimus, Aphelenchus, Aporcelaimus, Butlerius, Cephalobus, Laimydorus, Mesodorylaimus, Mononchus, Prismatolaimus, dan Rhabditis. Nematoda dengan populasi paling dominan pada daun adalah Rhabditis, akar oleh Helicotylenchus, dan tanah oleh Cephalobus. Kata kunci: fitonematoda, identifikasi, komunitas, Strawberry (Fragaria L.) is one of Indonesia's horticultural commodities with high economic value. One of the obstacles to strawberry cultivation is plant parasitic nematodes (phytonematodes). This study aimed to identify the genera of nematodes and estimate their populations in three major strawberry production centers in West Java. Samples of soil, roots, and leaves were collected purposively from both healthy plants and those showing disease symptoms. Nematodes were extracted using centrifugation flotation for soil samples, mist chamber for root samples, and water immersion for leaf samples. Nematodes were identified morphologically. Nematode community analysis was conducted by calculating Shannon-Wiener diversity index, evenness index, dominance index, maturity index (MI), plant parasite index (PPI). The phytonematodes identified were Aphelenchoides, Criconemella, Helicotylenchus, Hemicycliophora, Meloidogyne, Paralongidorus, Pratylenchus, Rotylenchulus, Rotylenchus, Scutellonema, Tylenchus, and Xiphinema. The non parasitic nematodes identified were Alaimus, Aphelenchus, Aporcelaimus, Butlerius, Cephalobus, Laimydorus, Mesodorylaimus, Mononchus, Prismatolaimus, and Rhabditis. The nematode with the most dominant population in leaf samples was Rhabditis, roots by Helicotylenchus, and soil by Cephalobus. Keywords: community, identification, phytonematodes
Keyword: phytonematodes, : community, identification

Judul: Best Difference Equation Aproximation to Duffing 's Equation
Abstrak: Persamaan Duffing merupakan persamaan yang sering muncul sebagai model masalah sistem ayun mekanis atau pada masalah rangkaian listrik. Umumnya penyelesaian persamaan ini secara numerik memberikan hampiran dengan gala! yang tinggi, seperti dengan metode Runge-Kutta. Tulisan ini mengkonstruksi suatu persamaan beda untuk menghampiri persamaan Duffing tersebut. Penyelesaian dari persamaan beda ini melibatkan fungsi-fungsi eliptik Jacobi. Berdasarkan penyelesaian ini diperoleh basil bahwa penyelesaian hampirannya persis sama dengan penyelesaian analitiknya. Penyelesaian analitik yang diperolehjuga melibalkan fungsi-fungsi eliptik Jacobi.
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