Judul: Pyrilla perpusilla Walker (Hemiptera: Fulgoridae) on Sugarcane (Saccharum officinarum Linn.): Biology, Symtomps, and Natural Enemies
Abstrak: Tebu (Saccharum officinarum Linn.) termasuk dalam Famili Poaceae dan umumnya digunakan sebagai bahan baku pembuatan gula. Tebu memiliki nilai ekonomis yang tinggi, sehingga produktivitas tebu diupayakan agar mengalami peningkatan. Pyrilla perpusilla dari Famili Fulgoridae merupakan salah satu hama tebu yang berpotensi menyebabkan kerugian. Penelitian ini bertujuan untuk mempelajari biologi, gejala serangan, dan musuh alami P. perpusilla. P. perpusilla diambil dari Desa Situ Daun, Kecamatan Tenjolaya, Kabupaten Bogor. Pemeliharaan dilakukan pada pot berkurungan yang telah ditanami tebu. Pengamatan biologi dilakukan pada 20 individu dari telur hingga imago. Pengamatan morfologi dilakukan pada 15 individu pada setiap fase. Hasil penelitian menunjukkan bahwa telur berlangsung selama 13 hari dengan panjang rata-rata 1,23 ± 0,02 mm. Nimfa terdiri atas lima instar, panjang rata-rata nimfa instar V 5,22 ± 0,30 mm. Imago P. perpusilla memiliki sayap cokelat dengan bintik-bintik hitam. Ujung abdomen imago betina memiliki sepasang bantalan dari lilin, sedangkan imago jantan memiliki ujung abdomen silinder. Siklus hidup P. perpusilla berlangsung selama 84 hari. Gejala serangan P. perpusilla antara lain daun menguning, menggulung, dan layu. Musuh alami P. perpusilla yaitu Hirsutella citriformis, Metarhizium sp., dan parasitoid telur (Hymenoptera: Eulophidae)., Sugarcane (Saccharum officinarum Linn.) belongs to the Poaceae Family and is generally used as a raw material for sugar-making. Sugarcane has a high economic value, so efforts are being made to increase its productivity. Pyrilla perpusilla from the Fulgoridae Family is a potential sugarcane pest that causes losses. The research aimed to study the biological aspects of P. perpusilla, symtomps, and its natural enemies. P. perpusilla was taken from Situ Daun Village, Tenjolaya District, Bogor Regency. Mass rearing was done on sugarcane in plastic caged pots. Biological observations were made on 20 individuals from egg to adult stages. Morphological observations were carried out on 15 individuals on each stage. The results showed that P. perpusilla egg lasts 13 days with an average length of 1.23 ± 0.02 mm. Nymph consisted of five instars. Average body length of 5th instar was 5.22 ± 0.30 mm. Adult had brown wings with black spots. Female adult's abdominal tip had a pair wax, while male adults had cylindrical abdominal tip. The life cycle of P. perpusilla lasts 84 days. Attack symptoms of P. perpusilla were yellowing leaves, wilt, and curl. Natural enemies of P. perpusilla were Hirsutella citriformis, Metarhizium sp., and egg parasitoid (Hymenoptera: Eulophidae).
Keyword: Auchenorrhyncha, life cycle, morphology, planthopper, poaceae

Judul: Hama-Hama pada Tanaman Tebu (Saccharum officinarum) di PG Madukismo PT Madubaru Yogyakarta
Abstrak: Tebu (Saccharum officinarum) merupakan salah satu komoditas perkebunan unggulan yang mempunyai peranan penting sebagai bahan baku produksi gula. Budi daya tebu tidak lepas dari serangan organisme pengganggu tanaman (OPT), terutama hama. Informasi mengenai hama spesifik lokasi penting diketahui sebagai rujukan dalam melakukan pengendalian di lokasi tersebut. Penelitian ini bertujuan mengetahui berbagai jenis hama pada tanaman tebu dan intensitas serangan hama utama di PG Madukismo, PT Madubaru, Yogyakarta. Penelitian diawali dengan menentukan tanaman contoh menggunakan metode diagonal. Pengamatan hama dilakukan dalam interval waktu dua minggu sebanyak empat kali meliputi koleksi, identifikasi hama, pencatatan gejala kerusakan yang ditimbulkan, dan menghitung intensitas serangan hama. Tahap identifikasi dilakukan di Laboratorium Invertebrata Hama, Departemen Hama dan Penyakit Tanaman, Fakultas Pertanian, Universitas Gadjah Mada dan Laboratorium Biosistematika Serangga, Departemen Proteksi Tanaman, Fakultas Pertanian, Institut Pertanian Bogor. Hama yang ditemukan menyerang tanaman tebu selama pengamatan, yaitu Lepidiota stigma (Coleoptera: Scarabaeidae), Euchlora viridis (Coleoptera: Scarabaeidae), Chilo sacchariphagus (Lepidoptera: Crambidae), Scirpophaga excerptalis (Lepidoptera: Crambidae), Rattus argentiventer (Rodentia: Muridae), Saccharicoccus sacchari (Hemiptera: Pseudococcidae), Pyrilla perpusilla (Hemiptera: Fulgoridae), dan Valanga nigricornis (Orthoptera: Acrididae). Uret (Lepidiota stigma dan Euchlora viridis) adalah hama yang paling dominan dengan intensitas serangan tertinggi.
Keyword: attack intensity, Lepidiota stigma, Rattus argentiventer

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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