Judul: Populasi dan Musuh Alami Telur Penggerek Batang Jagung Asia Ostrinia furnacalis Guenée (Lepidoptera: Crambidae) di Wilayah Bogor
Abstrak: Ostrinia furnacalis Guenée is one of the most important pests of corn in Asia. However, the infestation by this pest in Bogor is low and it is supposed that O. furnacalis population is lowered by natural enemy such parasitoid, predator, or pathogen. This research studied the egg population and biotic factors affecting its development in the field. Observations have been carried out in six villages of six sub-district of Bogor regency. The result showed that six egg clusters have been found in 371 m2 corn field. No differences have been showed by different plant age. Percentage of parasitism by Trichogramma sp. reached 19.90%. While entomopathogenic fungi Fusarium sp. attacked 25.16% egg population. Other minor natural enemy is predatory mite.
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Judul: Penggerek Batang Jagung Ostrinia furnacalis Guenée (Lepidoptera: Crambidae): Tingkat Serangan di Wilayah Bogor dan Siklus Hidupnya di Laboratorium
Abstrak: In Indonesia, corn (Zea mays L.) is used as the second largest food crop after rice. Corn is also important source of animal feed and vegetable oil. The productivity of corn crop often lowered by the infestation of the asiatic corn borer (ACB) Ostrinia furnacalis Guenée (Lepidoptera: Crambidae) and losses due to this pest could reach 20-80%. The purposes of the study are to survey the degree of field infestation by ACB in Bogor area and to investigate the ACB life cycle in the laboratory. Field study was carried out in 15 villages where corn was planted. The presence of the hole and the frass on the corn stalk were observed. Secondary data of agronomy practice were also gathered by interviewing the farmer. Of 75 plant samples that have been determined sistematically on each plot, 52% (the highest) were infested by ACB in village Cikarawang, 6.7% in village Babakan, Neglasari, and Cihideung Udik. No ACB infestation was detected in village Mekarsari. Other villages showed different degree of infestation between 8.3-44%. The different degree of ACB infestation amongst the observed villages did not correlate with the different of plant variety, applied pesticide, and time planting. In the laboratory the ACB eggs hatched in 4 days. By using the artificial diet for larvae, the stadia of instar I was 3-6 days, instar II was 2-5 days, instar III was 2-7 days, instar IV was 2-7 days, instar V was 5-11 days. The ACB took pupal stage during 6-8 days. The longevity of the ACB adult was 9-15 days. The sexual dimorphism was observed: the size of male pupa and adult was smaller than female, the color pattern of front wing of the male was darker than that of female, and the different form of exterior genital sign.
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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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