Judul: Population Development of Aphis gossypii G. and Predators on Monoculture and Intercropping Chili in Cikandang Village, Cikajang District, Garut
Abstrak: Aphis gossypii Glover merupakan hama penting yang menyerang tanaman cabai dengan cara menusuk dan mengisap cairan tanaman dan juga berperan sebagai vektor virus penyakit tanaman. Selain kutudaun, keberadaaan predator di lahan juga berperan penting dalam pengendalian kutudaun secara alami. Tujuan penelitian mengetahui perkembangan populasi kutudaun dan predatornya pada pertanaman cabai monokultur dan tumpang sari di Desa Cikandang, Kecamatan Cikajang, Garut. Penelitian dilaksanakan pada bulan Mei sampai dengan Juli 2021 yang meliputi pengamatan kutudaun dan predator, identifikasi, dan analisis data. Pengamatan dilakukan secara langsung dengan metode acak sistematis (jarak antar baris satu baris tanaman dan jarak dalam baris lima tanaman). Jumlah tanaman contoh setiap lahan 100 tanaman. Pengamatan kutudaun dilakukan dengan mengamati lima helai daun cabai tiap tanaman contoh sedangkan predator dilakukan dengan mengamati seluruh bagian tanaman contoh. Hasil penelitian menunjukkan bahwa populasi nimfa dan imago A. gossypii yang ditemukan pada pertanaman cabai monokultur dan tumpang sari berfluktuasi. Predator A. gossypii yang ditemukan di antaranya Episyrphus sp., Micromus sp., dan Menochilus sexmaculatus. Populasi A. gossypii pada pertanaman cabai monokultur lebih tinggi dibanding cabai tumpang sari. Begitu pula dengan populasi predatornya lebih banyak ditemukan pada pertanaman cabai monokultur dari pada cabai tumpang sari., Aphis gossypii Glover is the main pest that attacks chili plants by piercing and sucking the plant fluids and also acts as a vector for plant disease viruses. Besides the aphids, the presence of predators in the field also has an important role in the natural control of aphids. This study aimed to determine the development of aphids populations and its predators in monoculture and intercropping chili in Cikandang Village, Cikajang District, Garut. The research conducted from May to July 2021, included observations of aphids and its predators, identification, and data analysis. The observation was conducted directly by systematic random sampling (the distance of each row was one row plants and the distance in rows were five plants) and the plant sample in each field was 100 plants. The observation of aphids was conducted by observing five chili leaves for each plant sample, while for its predators were conducted by observing all parts of the plant sample. The results showed that the population of nymphs and adult A. gossypii found in the monoculture and intercropping chilies fluctuated. The predators of A. gossypii found were Episyrphus sp., Micromus sp., and Menochilus sexmaculatus. The population of A. gossypii in monoculture chili was higher than the intercropping chili. Similar for the predators population were more commonly found in the monoculture chilies than in the intercropping chilies.
Keyword: Aphis gossypii, intercropping, monoculture, predators

Judul: Biologi Dan Pertumbuhan Populasi Aphis gossypii Glov. (Homoptera : Aphididae) Pada Tanaman Melon (Cucumis melo) Timun (Cucumis sativus) Dan Gambas (Luffa clyndrica)
Abstrak: Penelitian ini bertujuan untuk mengetahui pengaruh tanaman inang yaitu melon, timun dan gambas yang tergolong dalam famili Cucurbitaceae terhadap biologi dan pertumbuh- an populasi A. gossypii. Identifikasi kutudaun dengan membuat preparat mikroskop, dan kemudian bagian-bagian kutudaun dicocokkan dengan kunci identifikasi pada Eastop (1961) dan Martin (1983). Penelitian ini meliputi siklus hidup, keperidian, lama hidup, praoviposisi, periode reproduksi, banyaknya nimfa rata-rata yang dilahirkan tiap hari, waktu perkembangan nimfa dan pertumbuhan populasi. Siklus hidup diamati setiap hari sejak infestasi sampai serangga melahirkan nimfa pertama kali. Keperidian diamati dengan menghitung banyaknya nimfa yang dilahirkan tiap hari, sampai imago mati. Pertumbuhan populasi diamati tiga hari sekali. Penelitian siklus hidup, keperidian, lama hidup, praoviposisi, periode reproduksi, banyaknya nimfa yang dilahirkan tiap hari, dan waktu perkembangan nimfa dilakukan sebanyak dua generasi, masing-masing generasi dengan ulangan 10 kali. Penelitian pertumbuhan populasi dilakukan satu generasi dengan ulangan tiga kali.
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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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