The Asian weaver ant, Oecophylla smaragdina, is known to have outstanding predatory power. This ant can protect the host plants from attacks of phytophagous insects and therefore has been used for biological control in the tropics. We present evidence for a possible negative effect of Oecophylla on the performance of host plants. Our observation in a fruit orchard of rambutan in Sumatra suggested that the presence of Oecohylla nests on the trees statistically significantly lowered the flower-visiting rate of flying insects, involving the major pollinator Trigona minangkabau. The visiting rate of Oecophylla workers to each flower shoot of rambutan significantly negatively correlated with the visiting rate of flying insects. Empirical evidence of such an inhibitory effect on flower-visiting of pollinators cased by aggressive ants has been scarce so far.

The fruit borer (Helicoverpa armigera Hubner) is one of the key pests of chili pepper in Indonesia. Yield loss due to this insect pest may reach up to 60%. Chemical treatment for controlling this insect pest is ineffective and eventually leads to environmental pollution. More environmentally safe insecticides are developed based on natural plant ingredients as their active compound such as essential oils. This study aimed to assess the potential of citronella oil for managing H. armigera on chili pepper. The experiments were conducted at the Indonesian A field experiment was designed in a randomized complete block design with five treatments and replicated five times. Citronella oil was extracted by steam distillation from Cymbopogon nardus. The oil was then chemically characterized by using GC-MS and its efficacy (ovicidal and feeding deterrent) against H. armigera was tested both in laboratory and field conditions. The GC-MS result showed that major chemical compounds of the citronella oil used were citronella (35.97%), nerol (17.28%), citronellol (10.03%), geranyle acetate (4.44%), elemol (4.38%), limonene (3.98%), and citronnellyle acetate (3.51%). The laboratory experiment revealed that the highest concentration (4,000 ppm) of citronella oil reduced egg laying by 53-66%. Ovicidal activity was concentration dependent, and egg hatchability decreased by 15-95% compared to control. The field experiment showed that treatment of citronella oil at 2.0 mL L -1 significantly reduced fruit damage by H. armigera similar to the plots treated with spinosad at the recommended dose (60 g ai ha -1 ). Application of citronella oil significantly reduced fruit damage by 72% and increased quality of the chili pepper. Because oviposition and feeding deterrent properties are key factors in controlling the pest, therefore this study revealed that citronella oil has potential to be incorporated into the controlling program of H. armigera on chili pepper.

<p>Perkembangan varietas-varietas bawang merah di suatu daerah ditentukan oleh keserasian dengan lingkungan, potensi hasil, toleransi terhadap serangan organisme pengganggu tumbuhan (OPT), serta umur dan mutu hasil. Penelitian bertujuan untuk menguji penampilan beberapa klon bawang merah dan hubungannya dengan intensitas serangan OPT penting. Penelitian dilaksanakan di Brebes dan Tegal (Jawa Tengah) dari Bulan Juni sampai dengan September 2011. Perlakuan yang diuji ialah 10 klon bawang merah hasil silangan tahun 2004 dan 2005, serta dua varietas bawang merah sebagai pembanding (Bauji dan Bima Brebes). Rancangan percobaan yang digunakan ialah acak kelompok dan diulang tiga kali. Parameter yang diamati ialah pertumbuhan tanaman (tinggi tanaman, jumlah daun, dan jumlah anakan), hasil panen, dan serangan OPT penting. Hasil penelitian menunjukkan bahwa klon no. 2005/1 dapat beradaptasi dengan baik di Brebes dan Tegal, mampu menghasilkan produksi tertinggi masing-masing sebesar 9,95 dan 17,50 t/ha, mempunyai diameter umbi terbesar (1,87 dan 2,41 cm), bentuk umbi bulat, dan berwarna merah tua, sedangkan klon no. 2004/11 mempunyai pertumbuhan dan  produktivitas yang tinggi, relatif toleran terhadap serangan Spodoptera exigua, Alternaria porri, dan Colletotrichum gloeosporioides, diameter umbi (1,67 dan 1,96 cm), bentuk umbi bulat,  dan berwarna merah tua, sedangkan klon no. 2004/10 dan no. 2005/19 sangat rentan terhadap serangan hama S. exigua, penyakit A. porri, dan C. gloeosporioides. Klon-klon yang mempunyai tingkat serangan rendah/toleran terhadap OPT merupakan klon harapan bawang merah toleran/tahan OPT. Namun demikian, penggunaan pestisida sesuai dengan konsep pengendalian hama terpadu (PHT) masih tetap diperlukan terutama apabila serangan OPT tersebut mencapai ambang pengendalian yang ditetapkan.</p><p> </p><p>The development of shallots varieties in one location depends on the genetic adaptability, yield potential,  tolerance to pest and diseases, harvest date, yield and quality. The aim of study was to evaluate 10 clones and two local clones as check, Bima Brebes and Bauji were conducted in Brebes and Tegal (Central Java) from June to September 2011. The trial were laid out in a completely randomized block design and each treatment was replicated three times. The parameters used for evaluating these clones were plant height, no. of sprout,  no. of leaves, yield and pests and diseases incidence. The results showed that considering overall performance, clone no. 2005/1 gave the highest yield (9.95 and 17.50 t/ha), and diameter of bulb (1.87 and 2.41 cm) in Brebes and Tegal respectively, clone no. 2004/11 produced growth and good yield  and showed tolerance to Spodoptera exigua, Alternaria porri, and Colletotrichum gloeosporioides, bulb diameter (1.67 and 1.96 cm) with dark red color,  while clone no. 2004/10 and no. 2005/19 were identified as the most susceptible clones to S. exigua, A. porri, and C. gloeosporioides. This suggests that some of shallots clones could be good candidates for the new varieties of shallots. However, the use of pesticides in IPM concept were still needed especially if the incidence of pests and diseases reach the action threshold.</p>

No abstract

Abshact Two sets of rainfall records previously published by Indonesian institutions were summarized to examine regional difference and seasonality ofrainfall in Java, especially sites in and around Bogor.