Judul: Effectiveness of P14 and J8 Bacteria as Biocontrol Agents Against Downy Mildew on  Cucumber in Tegal
Abstrak: Mentimun merupakan salah satu jenis sayuran yang populer ditanam di Indonesia. Salah satu faktor yang menurunkan produktivitas mentimun adalah penyakit tanaman. Penyakit penting yang menyerang daun yaitu penyakit downy mildew yang disebabkan oleh Pseudoperonospora cubensis. Pemanfaatan bakteri sebagai agens hayati merupakan salah satu alternatif pengendalian yang tidak berdampak negatif bagi lingkungan. Tujuan penelitian ini adalah mengetahui keefektifan dari bakteri agens hayati tunggal dan kombinasi P14 dan J8 terhadap penyakit downy mildew dan pengaruhnya terhadap pertumbuhan tanaman serta hasil mentimun di Kabupaten Tegal. Percobaan dilakukan dengan menggunakan dua bakteri galur P14 dan J8, yang terdiri dari empat taraf perlakuan. Perlakuan terdiri dari kontrol, perendaman benih dengan bakteri P14, bakteri J8, dan dengan kombinasi P14 dan J8. Penelitian disusun dalam rancangan acak kelompok (RAK) dengan enam ulangan. Isolat bakteri P14 dan J8 diproduksi massal kemudian diaplikasikan pada benih. Pengamatan dilakukan pada pertumbuhan tanaman mentimun, kemunculan pertama penyakit, nilai AUDPC, insidensi, keparahan penyakit, dan produksi mentimun. Hasil penelitian menunjukkan bahwa aplikasi tunggal atau kombinasi bakteri P14 dan J8 tidak mempengaruhi pertumbuhan tanaman kecuali perlakuan kombinasi bakteri P14 dan J8 mempengaruhi daya kecambah benih serta produksi mentimun meningkat. Aplikasi kombinasi P14 dan J8 mampu menekan penyakit downy mildew mentimun secara nyata dan meningkatkan hasil mentimun di Tegal., Cucumber is a type of vegetable crop popularly grown in Indonesia. One factor that decreases the yield of cucumber productivity is plant disease. An important disease that attacks leaves is downy mildew caused by Pseudoperonospora cubensis. The utilization of bacteria as biological agents is an alternative control with no negative impact to the environment. The purpose of this research was to determine the effectiveness of single biological agent bacteria and a combination of P14 and J8 against downy mildew disease and their effect on plant growth and cucumber yield. Experiment was conducted using two bacterial strains P14 and J8, consisting of four treatment levels. The treatments consisted of control, soaking the seeds with P14 bacteria, J8 bacteria, and with combination of P14 and J8. The research was arranged in randomized block design (RCBD) with six replication. Bacterial isolates P14 and J8 were mass produced and then applied by seed treatment. The observations were made on cucumber plant growth, the first symptoms that appear on plants, AUDPC value, incidence, disease severity, and cucumber production. The result showed that the single application or combination of P14 and J8 bacteria didn’t affect plant growth except the combination treatment of P14 and J8 bacteria affects seed germination. The application of the combination of P14 and J8 can significantly suppress the incidence and severity downy mildew of cucumber and increase cucumber yield in Tegal.
Keyword: biological control, cucurbitaceae, PGPR

Judul: Effectiveness of Bacteria Again Important Pests on Melon Plants Supervised
Abstrak: MERI ELIZA. Keefektifan Bakteri Agens Hayati terhadap Hama Penting pada Melon. Dibimbing oleh SURYO WIYONO dan BONJOK ISTIAJI. Penggunaan bakteri sebagai agen biokontrol termasuk upaya mengurangi dampak negatif penggunaan pestisida sintetik. Penelitian ini bertujuan untuk mengetahui efektivitas bakteri P14 dan J8 dalam mengendalikan hama. Penelitian ini dilakukan di perkebunan melon di Desa Jembayat, Kabupaten Tegal, Jawa Tengah pada bulan September hingga November 2021. Pengambilan data dilakukan secara langsung dengan mengamati gejala, tingkat kerusakan hama, serta menghitung populasi hama. Studi ini dilakukan denngan melihat pengaruh aplikasi agens biologis bakteri pada hama utama melon, yaitu kutu daun, kutu putih, lalat buah, dan kumbang daun. Percobaan disusun dalam Rancangan Acak Kelompok (RAK). Daerah penelitian terdiri dari lima blok sebagai ulangan, setiap blok berisi enam perlakuan yang ditandai dengan label.Hasil penelitian menunjukkan bakteri agens hayati P14 dan J8 menekan populasi kutu putih secara nyata pada umur 4 -7 minggu setelah tanam. Selain itu, bakteri P14 dan J8 juga berpengaruh terhadap peningkatan daya kecambah biji melon., MERI ELIZA. Effectiveness of Bacteria Agains Important Pests on Melon Plants. Supervised by SURYO WIYONO and BONJOK ISTIAJI. The use of bacteria as biocontrol agents includes efforts to minimize the negative impact of using synthetic pesticides. This study aims to determine the effectiveness of P14 and J8 bacteria to control pests. This research was conducted on a melon plantation in Jembayat Village, Tegal Regency, Central Java from October 2021 to November 2021. Data collection was carried out directly by observing the symptoms and the damage rate of pests, and calculating the population of pests. This study looked at the effect of the application of bacterial biological agents on major melon pests including aphids, mealybugs, fruit flies and leaf beetles. The experiments were arranged in a Randomized Block Design. The research area consists of five blocks as replicates, each block contains six treatments marked with the label. Research result show treatment of P14 and J8 bacteria agens hayati suppresses the population of mealybugs at some observation date In addition, P14 and J8 bacteria also had an effect on increasing the germination of melon seeds.
Keyword: induced resistance,, mealybugs, Plant Growth Promoting Rhizobacteria (PGPR)

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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