Sinergisme Jamur Entomopatogen Metarhizium anisopliae Dengan Insektisida Kimia untuk Meningkatkan Mortalitas Ulat Bawang Spodoptera exigua
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Indonesian Center for Horticulture Research and Development
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(Synergism Entomopathogenic Fungus Metarhizium anisopliae and Chemical Insecticide to Increase the Mortality of Armyworm, Spodoptera exigua)Hama ulat bawang Spodoptera exigua (Lepidoptera: Noctuidae) merupakan salah satu hama penting pada tanaman bawang di Indonesia. Jamur entomopatogen terutama Metarhizium anisopliae telah banyak digunakan untuk mengendalikan hama serangga. Keefektivitasan jamur entomopatogen M. anisopliae bila diaplikasikan secara tunggal untuk pengendalian hama hasilnya belum memuaskan. Oleh karena itu perlu dilakukan usaha untuk meningkatkan keefektifan jamur entomopatogen tersebut dengan melakukan pencampuran dengan insektisida kimia. Tujuan penelitian untuk mengetahui sinergisme campuran jamur entomopatogen M. anisopliae dengan insektisida kimia terhadap mortalitas larva S. exigua instar ke-3 di laboratorium. Percobaan dilaksanakan di Laboratorium Entomologi Balai Penelitian Tanaman Sayuran di Lembang ( ± 1.250 m dpl.), mulai bulan Juni sampai Oktober 2014. Larva S. exigua dikumpulkan dari pertanaman petani bawang merah di daerah Cirebon, Jawa Barat dan diperbanyak di Rumah Kasa Balai Penelitian Tanaman Sayuran. Penelitian dilaksanakan dalam dua tahap kegiatan, yaitu (1) uji pendahuluan dosis jamur M. anisopliae dan dosis insektisida kimia dan (2) uji campuran jamur M. anisopliae dengan dosis sublethal insektisida kimia. Rancangan percobaan yang digunakan adalah rancangan acak lengkap yang terdiri atas enam perlakuan dan empat ulangan. Penelitian menggunakan metode pencelupan. Mortalitas larva S. exigua diamati mulai 24 jam sampai dengan 168 jam setelah perlakuan. Data mortalitas larva diolah menggunakan analisis probit untuk menetapkan nilai LC50. Hasil analisis menunjukkan bahwa nilai LC50 insektisida kimia yang terendah diperoleh dari insektisida abamektin, yaitu 482,34 ppm dan yang tertinggi diperoleh dari jamur M. anisopliae, yaitu 1.189, 83 ppm. Nilai LC50 campuran insektisida, campuran jamur M. anisopliae dengan insektisida abamektin menunjukkan efek sinergistik dan meningkatkan efikasi 24,45 kali lipat jika dibandingkan dengan jamur M. anisopliae secara tunggal. Kombinasi jamur entomopatogen dengan insektisida konsentrasi sublethal dapat meningkatkan kemampuan jamur entomopatogen dalam mengendalikan S. exigua sehingga dapat memperlambat terjadinya resistensi insektisida.KeywordsSinergisme; Insektisida kimia; Jamur Metarhizium anisopliae; Mortalitas larva; Spodoptera exiguaAbstractThe beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae) is a serious pest of shallot in Indonesia. Many entomopathogenic fungi especially Metarhizium anisopliae are used as biological control agents of insects pests. But, the control of pest in crops with entomopathogens fungi, M. anisopliae alone is still not effective. Therefore it is necessary to improve the effectiveness of the entomopathogenic fungus by mixing with chemical insecticides. The aim of the study was to determine the sinergism of entomopathogenic fungi with insecticides to control third instar of S. exigua larvae under laboratory condition. The experiment was conducted at Indonesian Vegetables Research Institute Lembang (±1,250 m asl.), from June to October 2014. Sample of S. exigua larvae were collected from farmers’ field in Cirebon, West Java and mass production was carried in a screenhouse. Two bioassay steps were performed i.e. (1) preliminery test of entomopatogenic doses and insecticide doses and (2) the combination of sublethal doses of insecticide and several doses of M. anisopliae. The experimental design used was completely randomized design consisted of six treatments and four replications. Dipping method was used in this research. Mortality of S. exigua larvae was observed at 24 hours after exposures and repeated every 24 hours up to 168 hours of expo sures. The mortality data was analyzed using probit analysis to determine the LC50 values. The analysis showed that the LC50 value of the lowest chemical insecticides derived from insecticides abamectin that is 482,34 ppm and the highest obtained from the fungus M. anisopliae that is 1,189,83 ppm. Based on LC50 value of insecticides mixtures, the addition of abamectin insecticide to the entomopathogenic fungi, M. anisopliae, indicated synergism and increased their efficacy by 24,45 times higher, compared to M. anisopliae alone. Entomopathogenic fungi, M. anisopliae in combination with sublethal concentration of insecticides could increase the fungal ability in controlling S. exigua and also could be useful to abate insecticide resistance.
Keywords
Sinergism; Chemical insecticide; Metarhizium anisopliae fungi; Larvae mortality; Spodoptera exigua