The effect of host conversion on the diamondback moth (Plutella xylostella Linnaeus) life cycle and pesticide bioassay

• Main Authors: Ching-Yi Chen, 陳靜宜
• Other Authors: Fu-Hsiung Hsu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/53942106717478004358

碩士 === 國立嘉義大學 === 生物資源學系研究所 === 102 === The purpose of this studies were to investigate the impact of host plant transfer from common cabbage to Chinese cabbage, radish, rape on the life cycle of oligophagous crucifer pest, diamondback moth, in an incubator set at 25±1oC (12L: 12D), and two trials have been conducted. In addition, this study explored the changes of life cycle for continuing rearing diamondback moth for three generations. Finally, the bioassays of four concentrations of Bacillus thuringiensis and spinosad on the diamondback moth larvae were evaluated. In the host plant transfer, the results showed that the first-year trial, developmental stages from larvae, pupae, to adults have significantly different (P<0.05) among different host plants, however, no significant difference has found in the egg stage. For those larvae fed on cabbage, were significant longer (9.80 d) than those fed on Chinese cabbage, radish, and rape. The second-year (included the survival rate) results showed that after larval host plant changing, each larval instars and adult stages of development time were significantly different (P<0.05), with no significant differences egg and pupal stage. For those larvae continued fed on cabbage, their development period (9.84 d) was significant longer than those transferred to Chinese cabbage, radish, rapeseed. After the transfer of larval host plant the survival rate were higher than untransformed host plant survival rate, and the lowest was found on those larvae fed on rape (43.33%). Study of the continue rearing at the same common cabbage leaf for three generations, Significant difference were found on egg stage, first instar, adult stage, fecundity, hatching rate (P<0.05) not in larval and pupal stages. The inbreeding does affect the larval survival, with the highest on the second (91.67%), and gradually decreased to the lowest at fourth generations (48.33%). The results of the pesticides evaluation have showed that highest dead number (21.50±2.65) was observed when 2 and 3 instar larvae treated with 4000 times dilution of Bacillus thuringiensis. The highest dead number (22.00±2.58) was shown when 2 and 3 instar larvae treated with 750 times dilution of Spinosad. Above results have suggested crop rotation integrated into the diamondback moth control is able to obtain healthy crucifer vegetable products.