Judul: Kerentanan Plutella xylostella dari Garut, Jawa Barat, terhadap Lima Jenis Insektisida Komersial dan Ekstrak Tephrosia vogelii
Abstrak: Plutella xylostella is a major pest of cabbage worldwide which can reduce cabbage yield significantly. Farmers often use insecticides to control the pest, but intensive insecticide use can lead to the development of pest resistance to insecticides. This study was conducted to determine the susceptibility of P. xylostella from Garut, West Java, to five commercial insecticides, i.e. chloranthraniliprole, deltamethrin, emamectin benzoat, profenofos, and spinetoram, as well as to Tephrosia vogelii extract. The commercial formulations of those five insecticides and ethyl acetate T. vogelii leaf extract were tested against second instar larvae P. xylostella with a leaf-dip feeding method in which the feeding treatment was given for 48 hours. The number of dead larvae was counted daily until 96 hours after treatment (HAP), then larval mortality data were analyzed by the probit method. Based on LC95 at 96 JSP, deltamethrin and profenofos had low toxicity on P. xylostella larvae, while chloranthraniliprole was moderately toxic. LC95 of these insecticides were 3677.09, 10872.00, and 362.36 mg a.i./l, respectively, which were 367.7, 14.5, and 9.2-fold higher than their respective recommended field rates. On the other hand, P. xylostella larvae were still susceptible to emamectin benzoat, spinetoram, and T. vogelii extract. LC95 of emamectin benzoate and spinetoram were 9.28 and 3.63 mg a.i./l, respectively, which were 1.1 and 3.3-fold lower that their respective recommended field rate. Meanwhile, LC95 of T. vogelii extract was 2907 mg/l which was lower than that of deltamethrin and profenofos. In addition to lethal effect, emamectin benzoate and spinetoram could inhibit the formation of pupal development, whereas deltamethrin, emamectin benzoate, and profenofos caused in inhibition of adult emergence.
Keyword: susceptibility., commercial insecticides, cabbage pest,, botanical insecticide

Judul: Kerentanan Plutella xylostella dari Kecamatan Cipanas, Kabupaten Cianjur, Jawa Barat terhadap Lima Jenis Insektisida Komersial, Ekstrak Piper aduncum, serta Campuran ekstrak P. aduncum dan Tephrosia vogelii
Abstrak: Plutella xylostella merupakan hama penting pada tanaman famili Brassicaceae. Kerusakan akibat hama tersebut dapat menyebabkan kehilangan hasil secara signifikan. Penggunaan insektisida secara terus menerus oleh petani dapat menyebabkan terjadinya resistensi hama P. xylostella. Penelitian ini bertujuan menentukan kerentanan larva P. xylostella yang berasal dari Kecamatan Cipanas, Kabupaten Cianjur, Jawa Barat terhadap lima jenis insektisida komersial, yaitu deltametrin, emamektin benzoat, klorantraniliprol, profenofos dan spinetoram, ekstrak buah Piper aduncum serta campuran ekstrak buah P. adumcum dan daun T. vogelii. Pengujian insektisida dilakukan pada larva instar 2 P. xylostella menggunakan metode celup daun dengan pemberian daun pakan perlakuan selama 48 jam. Pengamatan mortalitas serangga uji dilakukan setiap hari hingga 96 jam setelah perlakuan (JSP), selanjutnya data dianalisis dengan metode probit. Deltametrin dan profenofos memiliki toksisitas yang rendah, sedangkan klorantraniliprol memiliki toksisitas yang sedang terhadap larva P. xylostella. LC95 profenofos dan klorantraniliprol pada 96 JSP masing-masing 18351.0 dan 131.1 mg b.a./L; nilai tersebut 24.5 dan 3.3 lebih tinggi daripada konsentrasi anjuran masing-masing. Lebih lanjut, larva P. xylostella masih rentan terhadap emamektin benzoat, spinetoram, ekstrak P. aduncum, serta campuran ekstrak P. aduncum dan T. vogelii. LC95 emamektin benzoat dan spinetoram masing-masing 1.17 dan 0.81 mg b.a./L; nilai tersebut 8.5 dan 14.8 lebih rendah daripada konsentrasi anjuran masing-masing. Sementara itu, campuran ekstrak P. aduncum dan T. vogelii (LC95 4759.80 mg ekstrak/L) lebih efektif daripada deltametrin dan profenofos serta ekstrak tunggal P. aduncum. Selain itu, perlakuan dengan klorantraniliprol, spinetoram, serta campuran ekstrak P. aduncum dan T. vogelii pada 3 taraf konsentrasi terendah menurunkan persentase pembentukan pupa dan kemunculan imago pada larva yang bertahan hidup sedangkan perlakuan dengan emamektin benzoat, profenofos, dan ekstrak tunggal P. aduncum tidak berpengaruh nyata. Berdasarkan hasil penelitian ini dapat disimpulkan bahwa larva P. xylostella asal Kecamatan Cipanas, Kabupaten Cianjur sudah tidak rentan terhadap deltametrin, klorantraniliprol, dan profenofos, tetapi masih rentan terhadap emamektin benzoat, dan spinetoram. Selain itu, campuran ekstrak P. aduncum dan T. vogelii dapat digunakan sebagai alternatif insektisida untuk mengendalikan hama P. xylostella.
Keyword: ekstrak campuran, hama kubis, insektisida komersial, insektisida nabati, kerentanan

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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