Judul: Biology and population abundance of spider mite tetranychus kanzawai (Acari: Tertanychidae) on Two cultivars of Jatropha curcas
Abstrak: Spider mite Tetranychus kanzawai is one of the most important pests attacking leaf of Jatropha curcas. Study was conducted with the objectives to elucidate life history parameters and abundance of spider mite on two Jatropha curcas cultivars. Field studies were carried out in BALITTRI Pakuwon Sukabumi, and laboratory experiments were conducted at the Department of Plant Protection, Bogor Agricultural University, from June to November 2008. Cultivars significantly affected some life history parameters of the spider mite. Spider mite reared on IP1 cultivar have longer oviposition period and higher fecundity than those on IP2 (7.00 days and 25.56 eggs against 5.00 days and 10.00 eggs). Intrinsic rate of increase was also higher on IP1. However, field studies indicated that the spider mite were less abundant on this cultivar. These might be due to the presence of other arthropods which were higher on IP1. In general, the highest population of spider mite occurred in August and the lowest in October- November.
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Judul: Keefektifan ekstrak tiga jenis tumbuhan terhadap Paracoccus marginatus dan Tetranychus sp. pada tanaman jarak pagar (Jatropha curcas L.)
Abstrak: Broad-spectrum synthetic pesticides which can cause some undesirable side effects, are commonly used by Jatropha curcas farmer. Thus, safe and effective alternatives need to be developed. The objective of this study was to evaluate the potential of extracts of three plant species, i.e. Piper retrofractum (fruits, direct extraction with ethyl acetate [EtOAc]), Tephrosia vogelii (leaves, direct extraction with EtOAc), and A. indica (seeds, sequential extraction with n-hexane, EtOAc, and methanol), to control Paracoccus marginatus and Tetranychus sp. on J. curcas. Based on LC50 and LC95 values, in general all test extracts were slightly more toxic to P. marginatus and Tetranychus sp. in the tests with residue-on-glass method than with leaf-residue method. In leaf-residue tests, P. retrofractum extract was about 3.3 to 8 times more toxic to P. marginatus (LC50 0.12%) and 1.3 to 21 times more toxic to Tetranychus sp. (LC50 0.22%) than the other test extracts. In residue-on-glass tests, P. retrofractum extract was about 2 to 6.8 times more toxic to P. marginatus (LC50 0.12%) and 6.8 to 11.7 times more toxic to Tetranychus sp. (LC50 0.18%) than the other test extracts. In greenhouse experiments on potted J. curcas, the treatment with P. retrofractum extract reduced the population of P. marginatus by 92.8% compared with control and that of Tetranychus sp. by 98%. This population reduction was better than or comparable with that in the treatment with a synthetic insecticide imidacloprid (78% and 94.7% reduction, respectively). The pest population reduction in the treatment with T. vogelii hexane A. indica extracts was much lower than that in the treatment with imidacloprid.
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Judul: Graf Pembagi-Nol Planar dan Tak-Planar
Abstrak: Graf pembagi-nol adalah suatu graf yang dibentuk dari himpunan pembaginol pada ring. Graf pembagi-nol terdiri atas himpunan simpul yang merupakan elemen-elemen pembagi-nol dari ring, serta dua simpul adjacent jika dan hanya jika hasil kalinya sama dengan nol. Graf pembagi-nol dapat digambarkan dalam sebuah bidang sedemikian rupa sehingga tidak ada dua sisi yang saling berpotongan. Graf pembagi-nol ini disebut sebagai graf planar. Karya ilmiah ini menjelaskan pembuktian teorema bahwa jika suatu graf pembagi-nol mempunyai graf yang isomorfik dengan graf lengkap dengan lima simpul atau graf bipartite lengkap dengan masing-masing himpunan simpul sebanyak tiga simpul, maka graf pembagi-nol ini bersifat tak-planar. Karya ilmiah ini juga membuktikan beberapa graf pembagi-nol merupakan graf planar atau tak-planar.
Keyword: ring, graf pembagi-nol, graf planar