• 作者： 鄭清煥
• 作者服務機構： 臺灣省農業試驗所嘉義農業試驗分所
• 中文摘要： 利用盆栽臺南五號及田間種植之相同稻種，於其分蘗初期、分蘗末期、孕穗初期、孕穗末期
  、乳熟期及糊熟期分別網罩不同數目之 3～4 齡褐飛蝨為害七天，結果發現稻穀損失按其重輕次
  序為分藥初期、孕穗初期、孕穗末期、乳熟期及分蘗末期，而以糊熟期受害損失最輕。各水稻生
  長時期遭受不同數目褐飛蝨為害 (X) 與產量損失百分率 (Y) 乃之關係，可用Y=AX 表示之。
  按褐飛蝨為害能力及稻穀價格、防治成本以及應予防治時田間褐飛蝨棲?的蟲齡分佈及食量計算
  ，褐飛蝨在本省目前的經濟為害水平　(Economic-injury levels)，暫定為自分?初期至乳熟期為
  3～7隻/叢，而糊熟期以後為5～9隻/叢。根據此項基準，於三處田間進行試驗，結果顯示每
  當褐飛蝨密度到達5隻/叢時即行施藥防治，所獲純收益最高，因此認為此項經濟為害水平可暫
  供為本省目前防治褐飛蝨之基準“
  .
• 英文摘要： Various population levels of 3rd-4th instarnymph of the brown planthopper (BPH) werecaged on single-hill pots as well as 20-hill plotof Tainan 5 rice plants at 6 different growingstages for a week period. The results revealedthat the severity of damage was in the orderof initial tillering, initial booting, maximun boo-ting, milky, maximun tillering, and doughy stage.Relationship between population levels of theinsect and yield reduction at different developedstage of rice followed an exponential pattern.Economic-injury levels were 3-7 insect/hillfrom initial tillering to milky stage and 5-9insect/hill from doughy stage to harvest of thecrop. These figures were calculated basing oncurrent rice price, cost of insect control and inconsideration of population structure and feedingamount of the insect when the control actionshould be made. In addition to above mentioned studies,three field experiments were conducted to con-firm the reliability of the economic-injury levelsdetermined above. These trials were set up indifferent localities in Chianan area in 2nd ricecrop 1978. Two insect susceptible cultivars,Tainan 5 and Tainong 67 and three insecticidesof different cost were used in this study. Theresults shown that insecticidal application assoon as the population of BPH reached thelevel of 5 insects per hill obtained the highestnet profit from all experimental sites. It in-dicated that the economic-injury levels deter-mined in this study are applicable in Taiwanpresently.
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