イチゴにおけるミカンキイロアザミウマFrankliniella occidentalis(Pergande)の被害解析  [in Japanese] Damage Analysis of the Western Flower Thrips, Frankliniella occidentalis(Pergande)(Thysanoptera : Thripidae) on Strawberry Plants  [in Japanese]

施設栽培イチゴ(品種 : 女峰)においてミカンキイロアザミウマを放飼し, 花, 幼果および成熟果の生息数と被害度の関係, 青色粘着トラップによる成虫捕獲数または花の成虫生息率と被害度の関係を解析した.1.花では雌成虫が, 幼果および成熟果では幼虫が主に生息した.果実では顎の隙間や種子形成部の窪み, マルチや葉に接した果実面に生息していた.2.被害度と成熟果, 1および2週間前の幼果における雄, 雌および幼虫生息数との重回帰分析の結果より, 被害度は主に成熟果の幼虫数によって規定された(R^2=0.775).3.花における成虫生息率(x)と1週間後の成熟果の被害度(ロジスティック変換値 : y)には有意な正の相関が認められ(y=0.00958x-0.847, R^2=0.627), 被害度5に対応する花の成虫生息率は21.6%であった.なお, この水準に基づく調査の必要サンプル数は59.4花であった.

Low, medium and high densities of the western flower thrips, Frankliniella occidentalis (Pergande), were established in three rooms of a greenhouse to analyze the effect of thrips densities on fruit damage to strawberry plants. Thrips densities were monitored weekly by counting the total number of thrips on flowers, immature fruit and mature fruit, and using blue sticky traps. Fruit damage index was calculated with 4 damage categories for mature fruits. On flowers and fruits (immature and mature), the dominant stages of thrips were adult females and larvae, respectively. Multiple regression analysis of the damage index for larvae, adult females and males on mature and immature fruits 1 week and 2 weeks before harvest showed that fruit damage to mature fruit was significant for larvae on mature fruits (R^2=0.775). Damage index (y) transformed to a logistic transformation also showed a significance in terms of percentage (x) of flowers infected with adults (y=0.00958x-0.847, R^2=0.627); the control threshold was 21.6% for a damage index of 5. For estimation at this threshold, the sample size was 59.4 flowers.