Judul: Eksplorasi dan Uji Potensi Nematoda Entomopatogen Heterorhabditis sp. terhadap Tenebrio molitor (Coleoptera: Tenebrionidae) secara In Vivo
Abstrak: Penggunaan insektisida sintetik mempunyai dampak negatif seperti pencemaran lingkungan, tertinggalnya residu pestisida, dan matinya beberapa musuh alami. Pentingnya pengendalian hayati akan terus bertambah pada saat sekarang ini. Terutama dalam pertanian berkelanjutan dan pengendalian hama yang ramah lingkungan. Upaya tersebut dapat dilakukan dengan menggali potensi organismeorganisme yang berasal dari lingkungan sekitar, antara lain nematoda entomopatogen (NEP) yang selanjutnya dimanfaatkan sebagai bioinsektisida. Penelitian ini bertujuan mengeksplorasi spesies-spesies nematoda entomopatogen yang efektif untuk pengendalian hama dengan menggunakan serangga uji Tenebrio molitor. Metode yang digunakan adalah: eksplorasi, identifikasi, dan uji efikasi. Eksplorasi dilakukan dengan menguji sampel tanah yang berasal dari wilayah Bogor dan Sukabumi. Setelah itu, uji efikasi dilakukan dengan menggunakan lima tingkat konsentrasi JI (Juvenil Infektif) 200, 400, 800, 1600, 3200 JI/ml. Persentase mortalitas dihitung pada jam ke-24, 30, 36, 42, 48, 54, dan 60 setelah infestasi JI. Nematoda entomopatogen yang di peroleh dari hasil eksplorasi teridentifikasi sebagai genus Heterorhabditis sp. dengan kemampuan mematikan serangga Tenebrio molitor pada kisaran kerapatan dan waktu uji, yaitu sebesar 42.85 % mortalitas tergolong sangat efektif dengan berkisar antara 96.67-100.00%, 5.71% mortalitas tergolong efektif dengan berkisar antara 76.67-80.00%, 11.42% mortalitas tergolong cukup efektif dengan berkisar antara 60.00- 70.00%, 5.71% mortalitas tergolong agak efektif dengan berkisar antara 40.00-43.33%, 8.57% mortalitas tergolong kurang efektif dengan berkisar antara 30.00-36.67%, dan 28.57% mortalitas tergolong tidak efektif dengan berkisar antara 0.00-23.33%. Berdasarkan nilai lethal concentration (LC) dan lethal time (LT) pada tingkat 50.00 dan 95.00%, tingkat kerapatan 1600 dan 3200 JI/ml adalah paling efektif.
Keyword: efikasi, eksplorasi, nematoda entomopatogen, ramah lingkungan, Tenebrio molitor

Judul: Patogenisitas dan keefektifan nematoda entomopatogen Heterorhabditis sp. terhadap penggerek umbi kentang Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)
Abstrak: Potato tuber moth, Phthorimaea operculella Zell. (Lepidoptera: Gelechiidae) is one of the important potato pest due to the potential loss can reach 100% if not well controlled. One of potential biological agents to control this pest is Entomopathogen Nematode Heterorhabditis. The effectiveness of Heterorhabditis has been studied to control several crop pests. Infective juveniles (IJ’s) of nematodes are able to find and penetrate the insects that live in the soil as well as in the plant tissues. The objective of this research is to study the pathogenicity of the Heterorhabditis sp. against P. operculella in the laboratory with direct and indirect (in the potato tuber) treatment. The experiments were conducted using completely randomized design with 6 treatments and 4 replications. The treatments were based on the density level of nematodes Heterorhabditis sp. (100, 200, 300, 400, and 500 IJ/ml) and the control. The result showed that P. operculella infected by Heterorhabditis sp. has symptoms by reducing the movement and feeding activity. The body of dead insects become soft and the color change to dark brown. For the direct treatment, Heterorhabditis sp. can kill P. operculella within 12 hours after application (HAA). At density level 100 IJ/ml, it can control P. operculella until 85% within 24 HAA. In contrast, the mortality rates of P. operculella in the indirect treatment (in the tubers) was 35% at doses of 1000 IJ/tubers.
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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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