TEKNOLOGI PENGENDALIAN HAMA Plutella xylostella DENGAN INSEKTISIDA DAN AGENSIA HAYATI PADA KUBIS DI KABUPATEN KARO - Loso Winarto; Darmawati Nazir (Balai Besar Pengkajian dan Pengembangan Teknologi Pertanian, 2004)
Plutella xylostella is the main pest of cabbage crops and it could cause harvest loss around 50 to 100 percentif no pesticides application. Most farmers in Karo District control the pest using various pesticides with highconcentration rates and short control interval that leads to high pesticide residual in cabbage crops and lowering exportcompetitiveness. The study was conducted in Karo District in 2001. P. xylostella was controlled using biologicalagents, namely Bacillus thuringiensis, Beauveria bassiana, farmers’ practice (using pesticides), control (no treatment).The assessment was carried out using demonstration plots. There were 18 participating farmers divided into 3 groups.Each group comprised 4,000 m2 of land including border plants and each group functioned as replication. Areas oftreatment plots were 650 m2 each, but those of control were 250 m2 each. Distance among treatment plots was 1.5meters, and distance between border and treatment plants was 1.5 meters. The results showed that B. thuringiensis, B.bassiana, and farmers’ practice could contain P. xylostella’s attack. Before treatments were carried out the populationof P. xylostella were 0.6, 0.8, and 0.6 larva per plant, and after treatments the population became 0 larva/plant.Population at control plots after treatment was 21.7 larva/plant. Leaves damage on 64 days after treatments was 0percent, while that of control was 74.35 percent. Yield of B. thuringiensis treatment was the highest (67,250 kg/ha),while those of B. bassiana and control were 66,000 kg/ha and 6,000 kg/ha, respectively. B. thuringiensis treatmentgained highest income of Rp 33,052,200 with B/C ratio of 2.36, followed by B. bassiana treatment (Rp 32.,128,800,and B/C ratio of 2.28), insecticides treatment (Rp 24,095.700, and B/C ratio of 1.39), and control (Rp 5,964,000, andB/C ratio of -0.59).Key words: cabbage, Plutella xylostella, Bacillis thuringiensis, Beauveria bassiana Dalam usahatani kubis masalah utama yang dihadapi petani adalah serangan hama. Salah satu hama utamakubis adalah Plutella xylostella. Serangan hama ini dapat mengakibatkan kehilangan hasil 50–100 persen apabila tidakdikendalikan. Pada umumnya petani Kabupaten Karo mengendalikan hama tersebut dengan menggunakan pestisidayang beraneka ragam dengan konsentrasi tinggi dan interval penyemprotan yang terlalu dekat, sehingga dapatmenimbulkan efek residu serta mengurangi harga saing ekspor. Untuk mengurangi adanya efek residu insektisida,maka BPTP Sumatra Utara telah melakukan pengkajian di Kabupaten Karo pada tahun 2001, mengenai pengendalianhama P. xylostella dengan agensia hayati menggunakan bakteri Bacillis thuringiensis, Beauveria bassiana, perlakuanpetani (insektisida ) dan kontrol (tanpa perlakuan). Pengkajian dilakukan dengan sistem demplot di lahan petani yangdiikuti 18 koperator, yang dibagi menjadi 3 kelompok. Masing-masing kelompok seluas 4.000 m2 termasuk tanamanpinggiran, tiap kelompok sebagai ulangan. Luas petak tiap perlakuan 650 m2 , kecuali kontrol 250 m2 , jarak antarperlakuan 1,5 m, jarak tanaman pinggiran dengan perlakuan 1,5 m. Hasil pengkajian menunjukkan bahwa perlakuanB. thuringiensis, B. bassiana dan perlakuan petani dapat menekan P. xylostella, sebelum aplikasi populasi larvamasing-masing mencapai 0,6 ; 0,8 ; dan 0,6 . Tetapi setelah aplikasi perlakuan yang ke 4 populasi larva P .xylostellamenjadi 0 larva/tanaman, perlakuan kontrol masih mencapai 21,7 larva/tanaman. Intensitas kerusakan daun saat 64hari setelah tanam (hst) masing–masing perlakuan 0 persen, kecuali perlakuan kontrol mencapai 74,35 persen.Produksi tertinggi terdapat pada perlakuan B. thuringiensis (67.250 kg/ha), B.bassiana (66.000 kg/ha), sedangkanperlakuan kontrol hanya mencapai 6.000 kg/ha. Hasil analisis usahatani menunjukkan bahwa pendapatan tertinggiadalah B.thuringiensis Rp 33.052.200 dengan B/C ratio 2,36 diikuti oleh B.bassiana Rp 32.128.800 dengan B/C ratio2,28; Insektisida Rp 24.095.70 dengan B/C 1,39 dan kontrol (tanpa perlakuan) Rp 5.964.000 dengan B/C ratio –0,59.Kata kunci : kubis, Plutella xylotella, Bacillus thuringiensis, Beauveria bassiana