Judul: Toksisitas Ekstrak Tephrosia vogelii dan Alpinia galanga terhadap Myzus persicae pada Tanaman Cabai
Abstrak: Red pepper (Capsicum annum) is one of the important agricultural commodities in Indonesia, but the production is still fluctuated. One of factor that cause the decline in productivity of red pepper is a disturbance of pests and diseases. Aphids Myzus persicae is one of the important pests on red pepper cultivation because it can cause loss of up to 80%. Botanical insecticide is one of alternative pest control agents which is biodegradable, safer than synthetic pesticides, and environmentally friendly. The objective of this study was to determine the effectiveness of two types of plant extracts as insecticides against M. persicae on red pepper (Capsicum annum) using the residual in plants methods and of systemic effects methods. Extracts used were Tephrosia vogelii and Alpinia galanga, each extract was tested using the residual and systemic methods. Extracts of T. vogelii showed a higher toxicity using both the residual and systemic methods with each LC95 values at 72 hours after treatment were 16 and 12 times more toxic than extracts of A. galanga. Systemic method was more efficient than the residual method. Testing of T. vogelii extract using systemic effect method LC95 8.5 times lower than using residual method on plant, as well as the test of A. galanga extract that the systemic method show more toxic than residual method.
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Judul: Efektivitas Streptomyces spp. sebagai Agensia Hayati Mikrob Patogen pada Tanaman Cabai Besar (Capsicum annuum)
Abstrak: Pepper is one of important horticulture plants but it’s productivity has decreased, due to microbial pathogens. Streptomyces spp. indigenous isolates have been reported to have capability to produce antimicrobial compounds. This research aimed to assess the ability of Streptomyces spp. LSW05 and PS4-16, two potential isolates based on previous in vitro assay, in controlling microbial pathogens, particularly Cercospora sp., in pepper plant in a field trial and to obtain an effective application method. The two isolates were applied singly or in combination using three methods (seed coating, soil drenching, and plant spraying). Streptomyces treatment significantly supressed disease severity and increased plant height and fruit production. Soil drenching with combination of the two isolates was the best treatment to suppress disease with the value of area under the disease progress curve (AUDPC) was only 234 with relative control effectiveness up to 81%. Plant sprayed with combination of the two isolates produced the highest fruits number (697 g/plot). Seed coated with PS4-16 isolate was the best treatment to increase plant height with the value of area under the height progress curve (AUHPC) was 1350, which was 27% higher than the non-treated plants. Seed coating with the combined isolates increased plant dry weight by 143%. Cost analysis showed that seed coating with the two isolates gave the highest profit as high as Rp 9.869.600 with relative control effectiveness up to 43%.
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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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