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

Abstract

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 (R2=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, R2=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.