Kajian ekologi Steinernema carpocapsae (All) sebagai agens pengendali hayati ulat jantung kubis (Crocidolomia binotalis Zell.)

SUBAGIYA, Promotor Prof.Dr.Ir. Soeparapto Mangundihardjo

2004 | Disertasi | S3 Ilmu Pertanian

Penelitian mengenai kajian ekologi Steinernema carpocapsae (All) sebagai agens pengendali hayati ulat jantung kubis (Crocidolomia binotalis Zell.) telah dilaksanakan di lapangan dan laboratorium. Tujuan penelitian adalah: 1) mempelajari hubungan antara suhu, kelembapan, dan kadar bahan organik tanah, serta kepadatan populasi serangga inang dengan populasi S. carpocapsae di pertanaman kubis; 2) mempelajari pengaruh suhu, kelembapan, dan kadar bahan organik tanah terhadap kemampuan bertahan hidup dan perkembangan populasi S. carpocapsae; 3) mengetahui tingkat virulensi nematoda S. carpocapsae dan bakteri Xenorhab-dus nematophilus Poinar & Thomas pada C. binotalis. Hasil penelitian lapangan menunjukkan bahwa penurunan populasi ulat C. binotalis di daun dipengaruhi oleh peningkatan populasi S. carpocapsae di daun. Besarnya populasi S. carpocapsae dalam tanah dipengaruhi oleh penurunan suhu tanah pada kedalaman 0-20 cm dan peningkatan kadar bahan organik tanah. Cara bertahan hidup S. carpocapsae pada suhu tinggi ± 35 °C) dilakukan dengan membentuk "berkas" (aggregate). S. carpocapsae yang hidup pada keadaan sedikit sumber nutrisi inang cenderung menyebabkan terbentulcnya larva stadium kedua yang menetas dan berkembang dalam ovarium induk betina. Di laboratorium, populasi S. carpocapsae berkembang secara maksimal pada suhu tanah 25 °C dan kelembapan tanah 60 %. Kadar bahan organik tanah yang tinggi cenderung menyebabkan tingginya populasi S. carpocapsae. Tipe tanah yang mengandung bahan organik tersusun oleh bangkai ulat C. binotalis merupakan media yang cocok bagi perkembangan S. carpocapsae. Suspensi larva S. carpocapsae pada konsentrasi 4000 ekor per ml air dan bakteri X nematophilus pada konsentrasi 15 X 105 colony forming unit (cfu) per 1 air menyebabkan kematian C. binotalis, masing-masing sebesar 72,92 % dan 51,57 %. Estimasi LC50 untuk C. binotalis oleh S. carpocapsae adalah 1782,92 ekor per ml air, sedangkan oleh X nematophilus adalah 920301,23 cfu per 1 air.

Studies on ecology of S. carpocapsae (All) as biological agent to control heart-cabbage caterpillar (Crocidolomia binotalis Zell.) were conducted in the cabbage farm and laboratory. The objectives of the research were to: 1) studies on the relationship between soil temperature, soil humidity, soil organic matter, the population density of host insect in cabbage plantation and the population density of S. carpocapsae; 2) studies on the effect of temperature, humidity, and soil organic matter to survival ability and population dynamic of S. carpocapsae; and 3) studies on the virulence of S. carpocapsae and X, nematophilus Poinar & Thomas on C. binotalis. The field research indicated that the increasing of population of S. car-pocapsae larvae on leaves would affect the reducing of population of C. binotalis caterpillar on leaves. Reducing of soil temperature at 0-20 cm depth and in-creasing of soil organic matter rate affected the increasing of population of S. car-pocapsae in land. To survive in soil where temperature of higher than 35 °C, the larvae formed themselves an aggregate. To overcome the limited availability of host nutrient source, the egg of S. carpocapsae tended to hatch the second larvae, which developed at the ovary of female adult. In laboratory, the population of S. carpocapsae developed maximally at soil temperature of 25 °C and soil humidity of 60 %. Higher rate of organic matter applied on soil tends to increase the population of S. carpocapsae. The type of soil composed consisting organic mater from insect cadaver of C. binotalis larvae, which was a good media for development of S. carpocapsae. The concentration level of S. carpocapsae at 4000 larvae per cc distillated water and X. nematophilus at 15 X 105 colony forming unit (cfu) per L of distillated water, could kill the larvae of C. binotalis as higher as 72.92 % and 51,57 %, respectively. The estima-tion of Lcm, on C binotalis by S. carpocapsae and X nematophilus, was 1782.92 larvae per cc of distillated water and 920.301 cfu per L of distillated water, respectively.

Kata Kunci : Hama Tanaman,Ulat Jantung Kubis,Pengendalian,Steinernema carpocapsae