| Summary: | 碩士 === 國立中興大學 === 昆蟲學系所 === 102 === Spodoptera litura (F.) and Plutella xylostella L. are important insect pests on agricultural crops in Asian countries. With the concern of food safety and environmental protection, biological control is good to reduce pesticide application. Knowing basic information of the predaceous bug, Eocanthecona furcellata, can provide us a comprehensive understanding of its population growth potential on different preys. In this study, the performance of E. furcellata reared on the tobacco cutworm and diamondback moth was conducted in laboratory at 25 ± 1?C, 60 ± 10% RH, and a photoperiod of 12:12 (L:D). According to the age-stage, two-sex life table, the intrinsic rate of increase, finite rate, and net reproductive rate were higher on P. xylostella (0.1389 d-1, 1.1490 d-1, 292.4 offspring) than on S. litura (0.1220 d-1, 1.1298 d-1, 272.3 offspring). The mean generation time was longer on S. litura (45.8 d) than on P. xylostella (40.8 d). However, the net predation rates were 644.1 larvae and 863.1 larvae on P. xylostella and S. litura, respectively, therefore, our study suggested that E. furcellata is more devouring and has better control potential on S. litura than on P. xylostella. Additionally, for mass rearing system, using the diamondback moth as food source was a better and economical method. In greenhouse, the predation capacity of E. furcellata on S. litura was evaluated with adults or the 3rd instar nymphs at three release rates, i.e. 1, 3, 5 adults or 5, 15, 25 nymphs as low, medium and high rates, individually. Releasing either nymphs or adults at medium and high rates had significantly decreasing the abundance of S. litura larvae on the 10th day after application. The mean survival rates of released nymphs and adults among three rates were 40~85% and 75~100%; the mortality was caused by the cannibalism among nymphs or the attack by larvae of S. litura. On the view of cost and benefit, the nymphs would be the better option agents to be released, in spite of the higher predation of adults. Additionally, the flight ability of adults may make them move out of the expected controlled-area, even the pests were still there. However, this scenario would not happen in the immature stages, thus the control efficacy would be promised while releasing nymphs. We recommend that the release rate should be one adult or nymph once S. litura reaching the density of 6 larvae or 2 larvae per cabbage plant in greenhouse.
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