PATOGENISITAS DUA ISOLAT LOKAL JAMUR Nomuraea rileyi (FARLOW) SAMSON TERHADAP Helicoverpa armigera HUBNER (LEPIDOPTERA: NOCTUIDAE)

IGAA. INDRAYANI, HERI PRABOWO, SRI MULYANINGSIH

Abstract


ABSTRAK
Epizootik Nomuraea rileyi telah berkembang secara alami dalam
populasi lebih dari 30 spesies serangga inang, termasuk H. armigera.
Penelitian ini dilakukan di Laboratorium Patologi Serangga Balai
Penelitian Tanaman Pemanis dan Serat Malang mulai Januari hingga
Desember 2011, tujuannya untuk mengetahui patogenisitas dua isolat lokal
jamur entomopatogen N. rileyi terhadap larva H. armigera. Penelitian
terdiri 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: 2,2
x 10 5 ; 4,5 x 10 5 ; 2,2 x 10 6 ; 4,5 x 10 6 ; 2,2 x 10 7 ; 4,5 x 10 7 ; 2,2 x 10 8 ; 4,5 x
10 8 konidia/ml, dan kontrol. Setiap perlakuan disusun dalam Rancangan
Acak Kelompok Faktorial dengan tiga kali ulangan. Aplikasi jamur pada
larva H. armigera dilakukan dengan metode kontaminasi permukaan
media yang berupa daun kapas muda (1cm 2 ) di dalam ruangan bersuhu
25±1⁰C dan kelembapan 75-80%. Parameter yang diamati adalah
mortalitas larva, LC 50 dan LT 50 , serta bobot larva. Hasil penelitian
menunjukkan bahwa tingkat patogenisitas isolat ML 01 terhadap larva H.
armigera lebih tinggi dibandingkan dengan isolat LG 02. Isolat ML 01
menyebabkan mortalitas larva H. armigera antara 51,13-85,56% (LC 50  =
2,5 x 10 2  Konidia/ml) dan isolat LG 02 antara 43,36-78,90%, (LC 50  =
5x10 6  Konidia/ml). LT 50 isolat ML 01 antara 5,2-5,5 hari, sedangkan isolat
LG 02 antara 6,8-7,0 hari, terutama pada konsentrasi 2,2-4,5 x 10 8
konidia/ml. Terdapat korelasi positif yang erat antara konsentrasi konidia
dan mortalitas larva baik pada isolat ML 01 (r=0,975) maupun LG 02
(r=0,980), demikian pula antara konsentrasi konidia dan kehilangan bobot
larva pada isolat ML 01 (r=0,982) dan LG 02 (r=0,972).
Kata kunci: Helicoverpa armigera, Nomuraea rileyi, patogenisitas, isolat,
mortalitas

ABSTRACT
The epizootic of the fungi Nomuraea rileyi has naturally developed
in more than 30 species of insect host population, including cotton
bollworm, H. armigera. A study on pathogenicity of two local isolates of
Nomuraea rileyi (Farlow) Samson fungi against Helicoverpa armigera
(Hubner) (Lepidoptera: Noctuidae) was conducted at Insect Pathology
Laboratory of Indonesian Sweeteners and Fibers Crops Research Institute
(ISFCRI) in Malang from January to December 2011 in order to find out
the pathogenicity of the isolates against H. armigera larvae. This study
consists 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 conidia
concentrations, 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 ; 4.5
x 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 with
three replications. Suspense of conidia was applied by surface
contamination method of cotton leaf as medium at 25±1⁰C of temperature
and 75-80% of humidity. Parameter observed were larval mortality, LC 50 ,
LT 50 , and larval weight. Result showed that ML 01 isolate was more
pathogenic against H. armigera larvae than LG 02 isolate based on larval
mortality, LC 50 , and LT 50 . Percentage of mortality of H. armigera larvae
due 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 and
6.8-7.0 days, respectively.There are closest positive correlation between
conidia concentration and percentage of mortality on ML 01 (r = 0.975)
and LG 02 (r = 0.980) isolates as well as between conidia concentration
and 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


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DOI: http://dx.doi.org/10.21082/jlittri.v19n1.2013.1-7

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