Judul: Kerentanan Plutella xylostella dari Kejajar Dieng, Kabupaten Wonosobo, Jawa Tengah lterhadap Lima Jenis Insektisida Komersial dan Ekstrak Buah Piper aduncum
Abstrak: Plutella xylostella is an important pest of Brassicaceae vegetable crops that can reduce crop production significantly. In general, farmers use syntethic insecticides intensively to control the pest. However, this control tactic has some negative impacts including resistance in target pests. This study was conducted to determine the susceptibility of P. xylostella from Kejajar Dieng District, Wonosobo Regency, Central Java to five commercial insecticides, i.e. chloranthraniliprole, deltamethrin, emamectin benzoate, profenofos, and spinetoram, as well as Piper aduncum fruit extract as a botanical insecticide for alternative control means. The commercial insecticides and P. aduncum 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. Larval mortality was counted at 24, 48, 72, and 96 hours after treatment (HAT) and larval mortality data was analyzed with a probit method. Based on LC95 at 96 HAT, deltamethrin and profenofos had low toxicity on P. xylostella larvae. LC95 of these insecticides were 2030 and 8462 mg a.i./L, respectively, which were 203 and 11.3-fold higher than their respective recommended field rates. Meanwhile, P. xylostella larvae were still susceptible to the other three commercial insecticides and P. aduncum extract. LC95 of chlorantraniliprole, emamectin benzoate, and spinetoram were 23.07, 2.59, and 0.90 mg a.i./L, respectively, which were 1.73, 3.86, and 13.33-fold lower than their respective recommended field rates. On the other hand LC95 of P. aduncum extract (2288.39 mg/L) was lower than that of profenofos but was higher than that of the other four commercial insecticides. Meanwhile, LC50 of P. aduncum extract was much lower than that of deltamethrin and profenofos. Thus, P. xylostella from Kejajar Dieng District were not susceptible to deltamethrin and profenofos but still susceptible to the other three commercial insecticides. In addition, P. aduncum extract can be used as an alternative insecticide for the control of P. xylostella. In the treatment with three lowest concentrations, all test insecticides could kill P. xylostella larvae but did not inhibit pupation and adult emergence significantly in the surviving larvae.
Keyword: susceptibility., pupation and adult emergence, commercial insecticides, cabbage pest, botanical insecticide

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: 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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