PATOGENISITAS DUA ISOLAT LOKAL JAMUR Nomuraea rileyi (FARLOW) SAMSON TERHADAP Helicoverpa armigera HUBNER (LEPIDOPTERA: NOCTUIDAE) - INDRAYANI, IGAA.; PRABOWO, HERI; MULYANINGSIH, SRI (Pusat Penelitian dan Pengembangan Perkebunan)
ABSTRAKEpizootik Nomuraea rileyi telah berkembang secara alami dalampopulasi lebih dari 30 spesies serangga inang, termasuk H. armigera.Penelitian ini dilakukan di Laboratorium Patologi Serangga BalaiPenelitian Tanaman Pemanis dan Serat Malang mulai Januari hinggaDesember 2011, tujuannya untuk mengetahui patogenisitas dua isolat lokaljamur entomopatogen N. rileyi terhadap larva H. armigera. Penelitianterdiri atas dua faktor perlakuan, faktor 1 adalah dua isolat lokal N. rileyi,yaitu ML 01 dan LG 02, dan faktor 2 adalah konsentrasi konidia, yaitu: 2,2x 10 5 ; 4,5 x 10 5 ; 2,2 x 10 6 ; 4,5 x 10 6 ; 2,2 x 10 7 ; 4,5 x 10 7 ; 2,2 x 10 8 ; 4,5 x10 8 konidia/ml, dan kontrol. Setiap perlakuan disusun dalam RancanganAcak Kelompok Faktorial dengan tiga kali ulangan. Aplikasi jamur padalarva H. armigera dilakukan dengan metode kontaminasi permukaanmedia yang berupa daun kapas muda (1cm 2 ) di dalam ruangan bersuhu25Â±1â°C dan kelembapan 75-80%. Parameter yang diamati adalahmortalitas larva, LC 50 dan LT 50 , serta bobot larva. Hasil penelitianmenunjukkan bahwa tingkat patogenisitas isolat ML 01 terhadap larva H.armigera lebih tinggi dibandingkan dengan isolat LG 02. Isolat ML 01menyebabkan mortalitas larva H. armigera antara 51,13-85,56% (LC 50Â =2,5 x 10 2Â Konidia/ml) dan isolat LG 02 antara 43,36-78,90%, (LC 50Â =5x10 6Â Konidia/ml). LT 50 isolat ML 01 antara 5,2-5,5 hari, sedangkan isolatLG 02 antara 6,8-7,0 hari, terutama pada konsentrasi 2,2-4,5 x 10 8konidia/ml. Terdapat korelasi positif yang erat antara konsentrasi konidiadan mortalitas larva baik pada isolat ML 01 (r=0,975) maupun LG 02(r=0,980), demikian pula antara konsentrasi konidia dan kehilangan bobotlarva pada isolat ML 01 (r=0,982) dan LG 02 (r=0,972).Kata kunci: Helicoverpa armigera, Nomuraea rileyi, patogenisitas, isolat,mortalitasABSTRACTThe epizootic of the fungi Nomuraea rileyi has naturally developedin more than 30 species of insect host population, including cottonbollworm, H. armigera. A study on pathogenicity of two local isolates ofNomuraea rileyi (Farlow) Samson fungi against Helicoverpa armigera(Hubner) (Lepidoptera: Noctuidae) was conducted at Insect PathologyLaboratory of Indonesian Sweeteners and Fibers Crops Research Institute(ISFCRI) in Malang from January to December 2011 in order to find outthe pathogenicity of the isolates against H. armigera larvae. This studyconsists of two factors as treatment. The first factor was N. rileyi isolates,e.g. ML 01 and LG 02, and the second factor were eight conidiaconcentrations, viz. 2.2 x 10 5 ; 4.5 x 10 5 ; 2.2 x 10 6 ; 4.5 x 10 6 ; 2.2 x 10 7 ; 4.5x 10 7 ; 2.2 x 10 8 ; 4.5 x 10 8 conidia/ml, and one untreated control.Treatments were arranged in Factorial Randomized Block Design withthree replications. Suspense of conidia was applied by surfacecontamination method of cotton leaf as medium at 25Â±1â°C of temperatureand 75-80% of humidity. Parameter observed were larval mortality, LC 50 ,LT 50 , and larval weight. Result showed that ML 01 isolate was morepathogenic against H. armigera larvae than LG 02 isolate based on larvalmortality, LC 50 , and LT 50 . Percentage of mortality of H. armigera larvaedue to ML 01 and LG 02 infection were 51.1- 85.56% and 43.36-78.90%,respectively. The LC 50 of ML 01 and LG 02 isolates was 5.2-5.5 days and6.8-7.0 days, respectively.There are closest positive correlation betweenconidia concentration and percentage of mortality on ML 01 (r = 0.975)and LG 02 (r = 0.980) isolates as well as between conidia concentrationand larval weight loss on ML 01 (r = 0.982) and LG 02 (r = 0.972)isolates.Key words: Helicoverpa armigera, Nomuraea rileyi, pathogenicity,isolate, mortality