Further Evaluation in the Feeding Potential of the Predaceous Insects and Spiders in Association with Aphids Harmful to Apple and Pear Growing, and the Effect of Pesticides on Predators

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  • HUKUSIMA Syôzô
    Laboratory of Entomology, Faculty of Agriculture, Gifu University
  • KONDÔ Kazunobu
    Laboratory of Entomology, Faculty of Agriculture, Gifu University IHARA CHEMICAL Co., LTD.

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Other Title
  • アブラムシ捕食虫の摂食能力およびこれらに対する薬剤の影響の再検討
  • アブラムシ ホショクチュウ ノ セッショク ノウリョク オヨビ コレラ ニ タイスル ヤクザイ ノ エイキョウ ノ サイケントウ エイブン
  • Studies on the Insect Association in Crop Field 27
  • ほ場における昆虫群集の研究 第27報

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The predaceous insects and spiders in apple and pea orchards play together an important role in the natural control of arthropod pests. Among them, coccinellids and various kinds of spiders feed particularly on the pear aphid and apple leaf-curling aphid until the phytophagous mite attack the fruit trees. Considering this point, any soundly devised pest control schedule on orchard crops should be taken under the consideration of the advantage of natural control. Following the preceding test, to attain the above mentioned purpose, an attempt was made to evaluate the daily feeding ability of five predators, and further, limited test was taken on the effects of some pesticides commonly applied in the orchard area onthe predator population in the laboratory.<br>Both the adult coccinellids, Coccinella setempunctata bruckii and Harmonia axyridis, fed on about 38 aphids per day per individual, and it proved to be the most effective among the predators tested. While in average daily consumption of the other adult species, Propyraea japonica ate about 18 aphids, and similarly Misumena tricuspidata consumed in average 15 or so per day. But in marked contrast with the above amount of consumption, only one or one decimal five in average number of the alate or apterous aphids were eaten by adult Theridion octomaculatum per day.<br>In the further experiments on the toxic effect of some pesticides upon the useful predators, it was suggested that malathion appears to be quite clearly harmful in marked reduction of predator populations. Lead arsenate and glyodin, on the other hand, are only slightly toxic or innocuous to them. It can thus probably be said that the decrease of predators in crop fields by the application of potenticial insecticides may cause aphids to be set up the point of economical importance.

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