Analysis of the Damage on Citrus Root Caused by the Soil Inhabiting Insects

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  • YOSHIDA Masayoshi
    Laboratory of Applied Entomology, Faculty of Agriculture, Shizuoka University
  • ANDO Shunji
    Laboratory of Applied Entomology, Faculty of Agriculture, Shizuoka University

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Other Title
  • 土壌害虫によるミカン根部の被害解析
  • ドジョウ ガイチュウ ニ ヨル ミカン コンブ ノ ヒガイ カイセキ 2 ミカンネコナカイガラムシ ノ チュウスウ ト ヒガイ
  • II. Relationship between the Damage on Citrus Root and the Individual Numbers of the Citrus Ground Mealy Bug, <i>Rhizoecus kondonis</i> KUWANA
  • II. ミカンネコナカイガラムシの虫数と被害

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Abstract

Estimation of the damage on citrus root caused by the citrus ground mealy bug, Rhizoecus kondonis, was made with citrus seedlings cultured in the apparatus deviced by the senior author. When new roots grew, 50, 100, 200 or 500 individuals of insects were put into the upper part of each equipment respectively. Weight of new and old roots was measured at the 40th days after the start of rearing. As the number of insects increased, weight of new root decreased rapidly, but that of old one remained nearly invariable. This result implies that this species mainly injures new roots. The relation between the number of insects and the weight of new roots was shown by a smooth decreasing curve with a special index. Percentage of the damage to new roots measured in weight loss comparing with the non-damaged roots were about 12.0, 26.0 and 47.2% for the number of insects of 50∼100, 200 and 500, respectively. The damage in actual orchards should be very serious, because the individual number of 500 will be attained very rapidly by the high egg-production, unisexuality and fast development of this insect.

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