| By the method of fluorescent substance tracing the paper studied the nourishment relationship among the food chain :rice-pests-rice spiders. The result through quantitative analysis showed that :(1) the damage to rice plant of the main rice pests in 2000 late rice periodThe damage to rice plant of grubs of Cuaphalocrcis madinalis, Cincticeps(Uh1.), Sogatella furcifera and Nilaparvata Lugens Stal during the three rice growth stage(rice seedling, tillering stage and booting stage) was measured separately. The results in this experiment showed that under the concentrations of 15, 0. 5, 0. Img/L the fluorescent substance in the rice pests were significantly higher than the others. That accorded with the absorb curve of rice. The fluorescent substance concentration of the grubs of Cuaphalocrcis madinalis at tillering stage was significantly higher than at rice seedling as well as N. Cincticeps(Uh1.). The fluorescent substance concentration of Nilaparvata Lugens Stal on booting stage was significantly higher than Sogatella furcifera on tilloring stage. During rice seedling stage the fluorescent substance concentration of the grubs of Cuaphalocrcis madinalis was significantly higher than N. Cincticeps(Uh1.).During tilloring stage the fluorescent substance concentration of the grubs of Cuaphalocrcis madinalis was higher than N. Cincticeps(Uhl.) and N. Cincticeps(Uh1. )wassignificantly higher than Sogatella furcifera.(2) The nourishment relationship among the food chain of rice- Sogatella furcifera- Pirata subpiraticus in 2001 early rice priodThe damage to rice plant of Sogatella furcifera and the controlling ability to Sogatella furcifera of Pirata subpiraticus during the two rice growth stages(tasseling stage and maturing stage) was measured separately . The results in this experiment showed that the fluorescent substance content of the rice plant, Sogatella furcifera and Pirata subpiraticus obviously increased by degrees of the concentration of fluorescent substance from 20mg/L to 50mg/L to lOOmg/L. During the tassel ing stage the rice content of Sogatella furcifera taking was 0. 0636g per pest every 24 h, and the content of Sogatella furcifera Pirata subpiraticus taking was 0. 0336g per spider every 24 h, equaling 6-7 pests. During the maturing stage the rice content of Sogatella furcifera taking was 0. 0115g per pest every 24 h, and the content of Sogatella furcifera Pirata subpiraticus taking was 0.0416g per spider every 24 h, equaling 16 pests. Comparing the two stages, the fluorescent substance content of Sogatella furcifera per gram and Pirata subpiraticus per gram at maturing stage was significantly higher than tasseling stage .which is contrary to the rice plant.(3) The nourishment relationship among the food chain(rice-pests-rice spiders) during the five growing stages of rice in 2001 late rice periodDuring the tilloring stage the rice content of Sogatella furcifera taking was 11.339g/g every 24 h, and the ricecontent of Nilaparvata Lugens Stal taking was 17. 451, 17. 591, 13. 829, 8. 707g/g every 24 h during the booting stage, tasseling stage, milking stage and maturing stage. The rice content of N. Cincticeps(Uh1.) taking was 85. 469g/g every 24 h during the booting stage, which was significantly higher than the other pests.The content of Sogatella furcifera Pirata subpiraticus taking was 2. 763g/g every 24 h during the tillering stage, and the content of Nilaparvata Lugens Stal Pirata subpiraticus taking was 3. 083, 3.637, 3. 638 and 2. 8g/g every 24 h during the booting, tasseling, milking and maturing stage. The content of N. Cincticeps(Uhl. ) Pirata subpiraticus taking was 1.389g/g every 24 h during the booting stage.(4) The rice content taken by different instar of the main rice pests in late rice periodThere is a common order in the rice content taken by different instar of Sogatella furcifera, N. Cincticeps(Uhl.) and Nilaparvata Lugens Stal . 1-2 instar nymphae>3-4 instar nymphae>5 instar nymphae and imago per gram every 24 h, and the difference... |
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