PATOGENISITAS NEMATODA Heterorhabditis sp. TERHADAP KUMBANG DAUN KELAPA Brontispa longissima GESTRO

Abstract

ABSTRAK Suatu bioassay telah dilakukan di Balai Penelitian Tanaman Rempah dan Obat Bogor, dari bulan November 2010 sampai dengan Maret 2011, yang bertujuan untuk mengetahui potensi Heterorhabditis sp. dalam mengendalikan Brontispa longissima. Nematoda dipanen dengan cara meletakkan larva Tenebrio molitor mati terinfeksi nematoda patogen serangga (NPS) di atas kertas saring yang diletakkan di dalam cawan petri berisi 30 ml air. Juvenil infektif (JI) yang ada di dalam tubuh larva akan keluar dan hidup di dalam air. Suspensi JI kemudian dilarutkan 1.000 kali lalu populasinya dihitung di bawah mikroskop binokuler dan diulang 3 kali. Populasi JI diperoleh dengan melarutkan 10 ml suspensi dengan sejumlah air sehingga diperoleh populasi 7.000, 3.500, 1.750, 875, 438, dan 0 JI/ml air. Masing-masing perlakuan diujikan pada 10 ekor larva, pupa, dan imago dengan menyemprotkan 2 ml suspensi JI. Pengamatan mortalitas B. longissima dilakukan pada 24, 48, dan 72 jam setelah infestasi (JSI). Hasil penelitian menunjukkan bahwa patogenisitas Heterorhabditis sp. tertinggi pada stadia larva diikuti imago dan pupa. Pada populasi 3.500 JI/ml air kematian larva, imago, dan pupa pada 24 JSI berturut-turut sekitar 73, 63, dan 10%, berbeda tidak nyata dengan perlakuan 7.000 JI/ml air. LC 50  Heterorhabditis sp. terhadap larva, imago, dan pupa pada 72 JSI berturut-turut 1.492, 2.622, dan 800.818 JI/ml air. Kata kunci: Brontispa  longissima,  kelapa,  Heterorhabditis  sp., patogenisitas ABSTRACT In order to evaluate the potensial of Heterorhabditis sp. in controlling B. longissima bioassays was conducted in Indonesian Research Institute for Spices and Medicinal Crops, Bogor from November 2010 until March 2011. Infective juveniles (IJ) of the nematodes were harvested by putting dead Tenebrio molitor on a filter paper placed in a petri dish containing 30 ml of water. IJs in the larval body will then go out and live in the water. The suspension was then diluted 1,000 times and then population counted under a binocular microscope and repeated 3 times. IJ population is obtained by dissolving 10 ml suspension to obtain 7,000; 3,500; 1,750; 875; 438; and 0 IJs/ml of water. Each treatment was tested on 10 larvae, pupae, and adults by spraying 2 ml IJ suspension. Mortality observations were made at 24, 48, and 72 hours after infestation (HAI). The results showed that the highest Heterorhabditis sp. pathogenicity was found in larvae stadium followed by pupae and adult stadia. In the 3,500 IJ population/ml of water, larvae, imago, and pupae mortalities in 24 HAI were approximately 73, 63, and 10%, respectively and were not significantly different with 7,000 IJ/ml of water. LC 50 values of Heterorhabditis sp. on the larvae, adult, and pupae in 72 HAI were 1,492; 2,622; and 800,818 IJ/ml of water, respectively. Key words: Brontispa longissima, Cocos nucifera, Heterorhabditis sp., pathogenicity