Judul: Disease Intensity and Their Control Efforts of Bacterial Wilt and Anthracnose of Chili in Tanah Datar Regency, West Sumatra
Abstrak: Cabai merah (Capsicum annuum L.) merupakan salah satu komoditas hortikultura penting di Indonesia. Permintaan cabai yang tinggi sepanjang tahun baik dari masyarakat maupun industri pangan menuntut produksi dan produktivitas cabai yang stabil. Penanaman cabai masih menghadapi berbagai kendala yang dapat menyebabkan kehilangan hasil, antara lain masalah penyakit layu bakteri oleh Ralstonia solanacearum dan antraknosa Colletotrichum acutatum. Tanah Datar merupakan salah satu daerah yang potensial sebagai penghasil cabai di Sumatera Barat. Penelitian ini bertujuan untuk mengukur intensitas penyakit layu bakteri dan antraknosa pada pertanaman cabai merah (C. annuum L.) di Kabupaten Tanah Datar, Sumatera Barat dan menganalisis pengendalian secara kimiawi yang dilakukan petani setempat. Metode penelitian meliputi pengamatan intensitas penyakit di lapangan dan wawancara dengan 40 responden petani menggunakan kuesioner terstruktur. Hasil penelitian menunjukkan bahwa insidensi penyakit antraknosa mencapai 100% dan layu bakteri mencapai 60%. Severitas penyakit antraknosa mencapai 86,40%. Intensitas penyakit tersebut dapat menyebabkan kehilangan hasil yang tinggi. Upaya pengendalian penyakit yang dilakukan petani masih mengandalkan metode kimiawi. Sebagian besar 75% petani menggunakan pestisida sintetik secara intensif dan aplikasinya secara terjadwal. Bahan aktif yang paling banyak digunakan petani berturut-turut adalah: propineb 70%, mancozeb 82%, klorotalonil 77%, fluopikolid 62,5 g/l + promakokarb hidroklorida, dan azoksistrobin 200 g/l + difenokonazol 125 g/l., Red chili pepper (Capsicum annuumL.) is one of the important horticultural commodities in Indonesia. The high demand for chili throughout the year from both the public and the food industry demands stable chili production and productivity. Chili cultivation still faces various obstacles that can cause yield loss, including the problem of bacterial wilt disease by Ralstonia solanacearum and fungal anthracnose by Colletotrichum acutatum. Tanah Datar is one of the potential areas as a chili producer in West Sumatra. This study aims to measure the intensity of bacterial wilt and anthracnose on red chili (C. annualL.) in Tanah Datar District, West Sumatra and analysis of the chemical control carried out by local farmers. The research method included observing disease intensity in the field and interviewing 40 farmer respondents using a structured questionnaire. The results showed that the incidence of anthracnose disease reached 100% and bacterial wilt reached 60%. The severity of anthracnose disease reached 86.40%. The intensity of those diseases can cause high yield losses. Disease control efforts by farmers still rely on chemical methods. Most 75% farmers were using synthetic pesticides intensively and the scheduled application. The active ingredients mostly used by farmers were: propineb 70%, mancozeb 82%, chlorothalonil 77%, fluopicollid 62.5 g/l + promacokacarb hydrochloride, and azoxystrobin 200 g/l + diphenoconazole 125 g/l.
Keyword: Colletotrichum acutatum, fungisida sintetik, insidensi penyakit, Ralstonia solanacearum, severitas penyakit, disease incidence, disease severity, synthetic fungicides

Judul: Antagonistic Activity of Dark Septate Endophyte against Fusarium sp. Isolated from Wilted Chili Plants
Abstrak: Cabai (Capsicum annuum L.) merupakan salah satu komoditas pertanian yang bernilai tinggi, namun produktivitasnya seringkali terkendala oleh serangan layu fusarium. Beberapa kultur cendawan dark septate endophyte (DSE) dilaporkan dapat menekan pertumbuhan Fusarium spp., namun potensi DSE sebagai agen biokontrol layu fusarium pada cabai belum banyak diteliti. Dalam penelitian ini, dua isolat DSE (S51 dan Cladosporium sp. KSP1) dievaluasi potensi antagonisnya terhadap Fusarium penyebab layu bibit cabai. DSE diuji patogenisitasnya untuk mengonfirmasi bahwa DSE tersebut bukan patogen pada cabai. Sebanyak dua strain Fusarium sp. asal tanaman cabai dengan gejala layu fusarium diseleksi patogenisitasnya pada tanaman cabai berusia 2 minggu. Fusarium sp. yang menunjukkan sifat patogenisitas tinggi dipilih untuk uji antagonis dengan DSE. Hasil penelitian menunjukkan Fusarium sp. strain F1 memiliki patogenisitas yang paling tinggi pada bibit cabai. Inokulasi DSE pada benih cabai membuktikan DSE tidak memengaruhi daya kecambah cabai. Panjang tajuk serta panjang akar bibit cabai ini tidak berbeda nyata dengan kontrol, sehingga kedua strain DSE dinyatakan bersifat non-patogenik. Kedua strain DSE dapat menghambat pertumbuhan Fusarium sp. strain F1 secara in vitro dengan persentase penghambatan antara 18 – 23%. Penelitian lebih lanjut tentang efektifitas DSE dalam menghambat perkembangan gejala layu diperlukan sebelum DSE dinyatakan sebagai agen potensial pengendali layu fusarium pada cabai., Chili (Capsicum annuum L.) is a high-value commodity, but its productivity is often constrained by fusarium wilt attacks. The dark septate endophyte (DSE) have been reported to inhibit the growth of Fusarium spp., however the potential of DSE as a biocontrol agent for fusarium wilt in chili has not been investigated. In this study, two DSE strains (S51 and Cladosporium sp. KSP1) were evaluated for their antagonistic potential against Fusarium isolated from chili with wilt symptom. DSE was tested for pathogenicity to determine its virulence on chili plants. Two strains of Fusarium sp. that were obtained from wilted chili plants were examined for its pathogenicity on 2-weeks-old chili seedling. Fusarium which showed high pathogenicity was evaluated through antagonist test against DSE. The results showed that Fusarium sp. strain F1 has the highest pathogenicity. Both DSE strains had no effect on chili germination and were found to be non-pathogenic as shoot and root length of chili seedlings did not differ significantly from those of control. Both DSE were able to inhibit the growth of Fusarium sp. F1 in vitro about 18 to 23%. Further research is needed to determine the effectiveness of DSE in suppressing the development of wilt symptoms in chili plants.
Keyword: antagonist test, biocontrol agent, chili seedling, fusarium wilt, pathogenicity

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.
Keyword: