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|標題:||Studies on infection of Spodoptera litura with the entomopathogenic nematode, Steinernema carpocapsae|
|摘要:||本試驗研究蟲生線蟲，Steinernema carpocapsae All strain ，在室內
養者間感染斜紋夜蛾之效力及其對農藥之忍受性。 以S. carpocapsae感
用Nutrient broth 培養液培養，再採MacConkey''s agar 與 NBTA 二種培
Infection of the common cutworm, Spodoptera litura, with the entomopathogenic nematode,Steinernema carpocapsae All strain, was studies under laboratory conditions. Theinfectivity of S. carpocapsae cultured in vivo and in vitro to S. litura and itstolerance to pesticides were investigated in thes study. The last instar larvae of S. litura infected with infective juvenile (IJ) could pupate successfully and formed the nematode- containing natural capsules. The capsule is ready to apply to soik surface for infecting S.litura alrvae. Symbiotic bacteria of S. carpocapsae were isolated and cultured in nutrient broth and were found to be beneficial to the nematode culture in vitro.Identification of phase variants of the symiotic bacteria by MacConkey''s agar plate and NBTA plate revealed that all of them were primary form during 72hr culture.The artificial media for nematode culture were prepared with six selected basic substances.There were almost no IJs liberating from the media without inoculating symbioticbacteria before adding nematode suspension, but most of the nematodes were viable in media. The IJ production was best in the media mixed soy flour with cholestrol and inoculated symbiotic baceria before adding nematode suspension, 8.14*10^4 IJs/g being harvested during culturing for 15 days. The IJ production by both pig brainmedium and soy flour medium with cholestrol had a peak at day 17 after culture. The media mixed soy flour with pig brain by different ratios were also prepared for nematode culture. The best IJ production was found by the medium with the ratio of 1to 1, 6.83*10^4 IJs/g being harvested during culturing for 15 days.The LC50 values of of IJ cultured in vivo and in vitro for 3rd and 5th instar larvae were similar, butthe LT50 caused by IJ Cultured in vitro was longer. Tolerance of IJ cultured in vivo and in vitroto insecticides and herbicides were both lower than to nematicides. The IJs treated with various pesticides became pretzeltwist shape. The prepupae within 24 hr were infceted with 20IJs/0.1ml suspension, resulting in 84.6% pupation. The best production of IJs cultured in pupae was 3.97*10^4IJs/g, being able to leave host through spiracles or cuticular membrane. The nematode-containing pupae were stored at 25℃, 8 days, and then were placed onto the soil surface containing 9.09% water (W/W) for testing infectivity to 5th instar larvae of S. litura. The larval mrotality in soil was 95% after incubating for 72 hr. However the mortality declined after preserving at 1℃ for 3、5 and 7 days.The IJ production by culturing in 5th instar larvae had a peak at day 9 after culture, about 1.96*10^5 IJs/g being harvested. This is significantly different from that produced in other cultures.
|Appears in Collections:||昆蟲學系|
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