Virulensi jamur Metarhizium anisopliae terhadap ulat daun kubis Plutella xylostella

HARJAKA, Tri, Prof.Dr. Ambarwati Harsojo, M.Sc

2005 | Tesis | S2 Fitopatologi

Ulat daun kubis Plutella xylostella L. (Lepidoptera : Plutellidae) merupakan salah satu hama penting tanaman kubis. Salah satu cara pengendalian hama tersebut secara hayati adalah menggunakan jamur Metarhizium anisopliae (Metchnikoff). Tujuan penelitian ini adalah untuk mengetahui virulensi jamur M. anisopliae terhadap ulat daun kubis P. xylostella. Empat isolat jamur M. anisopliae yang diperoleh dari empat jenis inang digunakan dalam penelitian ini, meliputi isolat dari larva kumbang kelapa Oryctes rhinoceros (MaOr), larva Phillophaga helleri (MaPh), pupa kumbang air famili Dysticidae (MaDy) dan larva P. xylostella (MaPx). Masing- masing isolat dibiakkan pada medium potato dextrose agar (PDA), kemudian dilakukan karakterisasi morfologi dan pertumbuhannya yang meliputi morfologi koloni, bentuk konidum dan viabilitasnya. Masing- masing isolat selanjutnya dibuat suspensi dengan kerapatan 108 konidum/ml akuades steril dan diinokulasikan ke larva P. xylostella instar ketiga dengan metode pencelupan ulat dan daun kubis sebagai pakan. Isolat yang menunjukan viabilitas dan virulensi terbaik dilanjutkan uji patogenisitas untuk mengetahui LC50. Isolat M. anisopliae terpilih dibuat seri pengenceran 104-108 dan diinokulasikan ke larva P. xylostella instar ketiga, kemudian data mortalitas dilak ukan analisis probit Hasil penelitian menunjukan bahwa masing-masing isolat jamur M. anisopliae yang diisolasi dari empat jenis inang tidak menunjukan perbedaan bentuk konidium dan pertumbuhannya, tetapi ada perbedaan morfologi warna koloni dan viabiltasnya. Empat isolat jamur M. anisopliae mampu menginfeksi dan menyebabkan mortalitas larva P. xylostella. Jamur M. anisopliae yang diisolasi dari larva O. rhinoceros (MaOr) menunjukan virulensi yang paling tinggi, dengan viabilitas terbaik mencapai 95% dan pada konsentrasi 108 konidium/ml mampu menyebabkan mortalitas P. xylostella instar ketiga mencapai 100% pada tiga hari setelah inokulasi (hsi). Isolat MaPx menunjukan virulensi yang lebih rendah dengan viabilitas yang rendah. Viabilitas isolat MaPh, MaDy dan MaPx masing-masing 92%, 38% dan 25,7%, dan hanya mampu menyebabkan mortalitas 100%, 95% dan 86,7% pada tiga hs i. Isolat MaOr merupakan jenis yang paling virulen dengan LC50 tercapai pada konsentrasi 1,02 x 106 konidium/ml.

Diamondback moth Plutella xylostella L. (Lepidoptera : Plutellidae) (DBM) is a serious pest of crussiferous plants. An entomopathogenic fungi Metarhizium anisopliae (Metchnikoff) is one of the fungi which had been used to control it. The aim of the research was to study the virulence of M. anisopliae against DBM. Four isolates of M. anisopliae obtained from four kinds of insect were used in this research, include fungi isolated from rhinoceros bettle Oryctes rhinoceros (MaOr), white grub Phillophaga helleri (MaPh), pupae of Dysticid bettle (MaDy), and P. xyostella larvae (MaPx). All isolates were cultured in potato dextrose agar (PDA) to characterized their morphology and fungal growth include the colour of coloni, form of conidia and their viability. For testing virulence against DBM, all isolates were cultured on PDA for 21 days, harvested and suspented into steril water and the population density was adjusted from 104-108 conidia per ml densities. Each isolate was inoculated at third instar of DBM larvae by dipping method. Twenty DBMs and crussifeous leaf as diet were dipped into suspension of each conidia of fungi for five minutes. The isolate which showed the highest viability and virulence was used for patogenisity test to know the lethal dose (LC 50) of isolate by probit analysis. The results showed that all isolates of M. anisopliae isolated from rhinoceros bettle, white grub P. helleri, Dysticidae pupae and P. xylostella larvae were pathogenic against DBM. Morphological character include form of conidia and its growth were not different. The colour of some fungal coloni and conidia germination were different . Fungal isolate from rhinoceros bettle (MaOr) showed the highest virulence. The conidia germinated up to 95% and caused mortality up to 100% at 3 days after inoculation (DAI). The germination of conidia for isolate MaPh, MaDy and MaPx were 92%, 38% and 25,7% respectively.These, three isolates caused mortality up to 100% at 3 DAI, 95% at DAI and 86,7% at 3 DAI respectively. The lethal dose of fungal isolate M. anisopliae isolated from rhinoceros bettle against third instar P. xylostella larvae was at density of 1,02 x 106 conidia per ml density.

Kata Kunci : Hama Tanaman Kubis,Ulat Daun,Jamur Metarhizium Anisopliae