Judul: Tingkat Resistensi Helopeltis antonii (Hemiptera: Miridae) dari Tiga Lokasi Kebun Kakao di Jawa Barat dan Induksi Resistensi terhadap Tiga Golongan Insektisida
Abstrak: Pada tanaman kakao di Indonesia, Helopeltis antonii Signoret merupakan salah satu hama utama yang dapat menurunkan produksi sebesar 60%. Selama ini petani melakukan tindakan pengendalian H. antonii menggunakan insektisida sintetis. Namun penggunaan insektisida sintetis yang tidak bijaksana, seperti penggunaan dosis atau konsentrasi yang berlebih dan aplikasi yang terlalu sering dapat mendorong terjadinya resistensi H. antonii. Penelitian ini bertujuan menentukan tingkat resistensi populasi lapangan hama H. antonii dari tiga lokasi kebun kakao di Jawa Barat (Bogor, Ciamis, dan Sukabumi), menginduksi populasi laboratorium hingga menjadi resisten terhadap tiga bahan aktif yang mewakili tiga golongan insektisida, dan mempelajari pengaruh insektisida uji terhadap kebugaran relatif dari imago yang bertahan hidup pada populasi laboratorium yang diinduksi resisten. Serangga uji yang digunakan dalam penelitian ini terbagi menjadi dua kelompok, populasi laboratorium dan populasi lapangan. Insektisida yang digunakan meliputi insektisida berbahan aktif klorpirifos (organofosfat), lamda sihalotrin (piretroid), dan tiametoksam (neonikotinoid). Penelitian dilaksanakan dengan melakukan 3 kegiatan, yaitu uji resistensi, induksi resistensi, dan studi pengaruh insektisida terhadap kebugaran H. antonii. Pengujian resistensi dilakukan menggunakan 5 tingkat konsentrasi insektisida uji yang mengakibatkan mortalitas serangga uji dengan kisaran 5-95% berdasarkan uji pendahuluan. Pengamatan dilakukan dengan menghitung mortalitas serangga. Hubungan antara konsentrasi insektisida dan mortalitas serangga uji diolah dengan analisis probit. Induksi resistensi dilakukan dengan dipaparkannya 20 ekor nimfa instar-3 pada konsentrasi subletal (LC50 dan LC75) dari masing-masing insektisida uji. Nimfa populasi laboratorium yang hidup dipelihara dan kemudian keturunannya pada fase nimfa instar-3 kembali dipaparkan pada LC50 dan LC75 insektisida uji hingga beberapa generasi sampai nisbah resistensi (NR) ≥ 4. Karakteristik biologi yang diamati yaitu masa pre-oviposisi, masa oviposisi, fekunditas, fertilitas, lama hidup imago betina, dan rasio jenis kelamin. Populasi lapangan H. antonii dari lokasi Bogor telah resisten terhadap insektisida lamda sihalotrin (piretroid) dengan NR 4.2 kali, indikasi resisten terhadap klorpirifos (organofosfat) dan tiametoksam (neonikotinoid). Populasi lapangan asal Ciamis telah resisten terhadap insektisida lamda sihalotrin dengan NR 10.8 kali, indikasi resisten terhadap insektisida tiametoksam, dan rentan terhadap insektisida klorpirifos. Sedangkan populasi lapangan asal Sukabumi menunjukkan indikasi resistensi pada insektisida lamda sihalotrin dan tiametoksam, dan rentan terhadap insektisida klorpirifos. H. antonii populasi standar berkembang menjadi populasi yang resisten terhadap tiga bahan aktif insektisida dalam 3 sampai 4 generasi akibat pemaparan insektisida konsentrasi subletal (LC50 dan LC75). Pemaparan insektisida pada konsentrasi subletal juga berpengaruh pada kebugaran. Peningkatan keperidian dan jumlah keturunan terjadi pada populasi resisten yang dipapar insektisida lamda sihalotrin, sedangkan penurunan keperidian dan jumlah keturunan terjadi pada populasi resisten yang dipapar insektisida klorpirifos dan tiametoksam. Peningkatan jumlah jenis kelamin betina terjadi hanya pada populasi resisten yang dipapar insektisida klorpirifos.
Keyword: kebugaran, neonikotinoid, organofosfat, piretroid, resistensi serangga

Judul: Aktivitas Insektisida Ekstrak Buah Cabai Jawa (Piper relrojrac/lIl71, Piperaceae) terhadap He/ope/tis antonii Sign. (Hemiptera: Miridae)
Abstrak: Helopeltis antonii Sign. (Hemiptera: Miridae) is an important pest of cocoa, tea, and cashew nuts. This insect pest sucks shoot and nut saps of plants causing blackish brown spots. Application of synthetic insecticides is commonly used to control Helopeltis spp. due to insecticide fast action. However, use of synthetic chemical insecticides can cause pest resistance and resurgence and outbreak of secondary pests, killing of non-target organisms as well as environmental contamination. Therefore, it is necessary to search for environmental friendly strategy to control H. antonii. The objectives of this study were to test the toxicity of Piper retrofractum extract to H. antonii adults, evaluate the effect of sublethal concentrations of the extract on the number of progeny nymphs of H. antonii, and to evaluate the persistence of the extract against mortality and oviposition of H. antonii. Cucumber was used as an alternate host for mass rearing and testing medium. The study was conducted in several stages: insect rearing, extraction, toxicity test, effects of sublethal, and persistency test. Toxicity test of P. retrofractum extract was conducted at concentrations of 0.05%, 0.10%, 0.15%, 0.20%, 0.25% and 0.3% based on the result of preliminary test. The extract was diluted in a mixture of acetone, methanol, and Tween 80 (5:5:5 v/v) [final concentration of 1.2%] and then diluted with distilled water until the desired volume. In addition, control solution was also prepared containing distilled water and a mixture of acetone, methanol, and Tween 80 (5:5:2 v/v) 1.2%. For each treatment, 10 individuals of H. antonii adults were used with five replications. The effect of sublethal test was conducted at concentrations equivalent to LC25 and LC50. The extract was sprayed on the whole surface of cucumber. Then the treated cucumbers and fourth instar nymphs were put in a plastic container (13 cm and diameter 14 cm) and the insects were held for 48 hours. After 48 hours, the treated cucumbers were replaced with untreated cucumbers until the nymphs became adults. The adult insects were then paired to obtain 10 pairs for each concentration level and control. Each pair of adult insects was placed into plastic containers and fed with untreated cucumbers. All of the adult insects were maintained until they died. Observations were made by counting the number of progeny nymphs in each treatment. Persistence test of P. retrofractum extract was conducted at concentrations of 0.49% (LC95), 0.98% (2 x LC95) and control ([aceton + methanol + Tween 80,5:5:2] + distilled water). The test extract emulsions were put into a clear glass spray bottle then exposed under sunlight for 7 hours/day from 08:00 to 15:00 pm for 0, 1, 3, and 5 days. These extracts were subsequently used for testing of the effect on mortality and oviposition of H. antonii. In the mortality test, P. retrofractum extracts that had been exposed under sunlight for 0, 1, 3, and 5 days were sprayed on H. antonii using a hand sprayer. Ten H. antonii adults were used v for each treatment and each treatment was replicated five times. The percentage of mortality was counted at 1, 2, 3, 4,
Keyword: Botanical insecticide, mortality, oviposition, persistence

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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