Judul: Insecticidal activity of sugar-apple (Annona squamosa L.) seed extracts from different locations and synergism of the most active extract with spiked-pepper (Piper aduncum L.) fruit extract against Crocidolomia pavonana (F.) (Lepidoptera: Crambidae) larvae
Abstrak: Results of leaf-residue bioassays of methanolic sugar-apple (Annona squamosa L.) seed extracts from eight locations in Central Java and Papua showed that LC50 of the extracts against Crocidolomia pavonana larvae ranged from 27.6 to 374 ppm, whereas the range of LC95 was 160.8-6067.8 ppm. Sugarapple extract from Sumber Lawang-Blora, Central Java had the lowest LC50 value, while the extract from Cepu-Blora had the lowest LC95. The difference in the slope of probit regression of sugar-apple extracts resulted in the difference in LC95/LC50 ratio. Spiked-pepper (Piper aduncum L.) fruit extract (LC50 867 ppm and LC95 3122.7 ppm) was much less active than the most active sugar-apple extract. The mixture of sugar-apple seed extract and spiked-pepper fruit extract (1:10) (LC50 66.3 ppm and LC95 1686.9 ppm) had strongly synergistic joint action at LC50 level (combination index 0.30) but antagonistic at LC95 level (combination index 1.59). In a semifield experiment, addition of spiked-pepper extract, neem (Azadirachta indica) seed extract or an optical brightener did not significantly increase the effectiveness of sugar apple seed extract against C. pavonana larvae on polybagged chinese cabbage plants.
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Judul: Insecticidal activitiy of spiked pepper (Piper aduncum) extracts from riau on the cabbage head caterpillar (Crocidolomia pavonana)
Abstrak: Spiked pepper (Piper aduncum) is a potential source of botanical insecticides. Its insecticidal activity has been widely reported, but the insecticidal activity of this plant collected from different locations has not been much studied, especially in Indonesia. The objectives of this research were (1) to evaluate the toxicity of P. aduncum leaf and fruit extracts from Riau to Crocidolomia pavonana larvae, (2) to evaluate the effect of the four most active P. aduncum extracts on feeding activity of C. pavonana larvae, (3) to evaluate the persistence and phytotoxicity of the four most active P. aduncum extracts, and (4) to examine qualitative property of the test P. aduncum extracts. P. aduncum leaves and fruits collected from ten different locations in Riau were extracted with ethyl acetate using maceration method. The toxicity test was conducted using a residual leaf feeding method. Mortality data was recorded and analyzed using probit analysis. The feeding inhibition activity test of the four most active extract was conducted using a choice method at concentrations of LC25 and LC50. The feeding inhibition data were subjected to analisys of variance followed by Duncan’s multiple range test at 5% level. The persistence of the four most active P. aduncum extracts was tested at LC95 and 2 x LC95 levels using direct spray method on broccoli plants. Mortality data were analyzed by analysis of variance followed by Duncan's multiple test at the 5% level. The symptom of phytotoxicity on broccoli leaves was observed. Qualitative examination of extract components was done using thin layer chromatography technique. Where P. aduncum fruit oil containing 76% dillapiole was included in the TLC test for comparison. The results showed that P. aduncum extracts collected from ten different locations had strong insecticidal activity and are potential to be used as sources of botanical insecticides. Among 20 extracts tested, four extracts had the highest activity, i.e. fruit extract from XIII Koto Kampar (LC95 0.209%), Pekanbaru (LC95 0.211%), Bangkinang Barat A (LC95 0.212%), and Cerenti (LC95 0.216%). The four most active extracts showed antifeedant effect at LC50 level. These four extracts lost their activity after being exposed to sunlight for 24 hours. Plant extracts tested did not cause phytotoxic effect on broccoli. Qualitative examination show the same separation pattern.
Keyword: botanical insecticide, toxicity, persistence, phytotoxicity

Judul: igenvalues and Eigenvectors of Tridiagonal Matrix with Non Constant and Recurrent Diagonal Entries.
Abstrak: Matriks tridiagonal adalah suatu matriks yang mempunyai entri-entri bernilai nol kecuali pada diagonal utama, di bawah diagonal utama (subdiagonal) dan di atas diagonal utama (superdiagonal). Entri pada diagonal utama tidak konstan dan berulang. Setiap entri pada matriks tridiagonal ini adalah bilangan kompleks. Dalam karya ilmiah ini, akan dibuktikan 3 teorema untuk menentukan nilai eigen dengan 2 kasus dan 1 teorema untuk menentukan vektor eigen. Teorema pertama menentukan polinomial karakteristik dari matriks tridiagonal. Polinomial karakteristik dari matriks tridiagonal tersebut digunakan untuk menentukan nilai eigen pada teorema kedua dan ketiga serta menentukan vektor eigen pada teorema keempat
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