| Popis: |
The percentage loss of paddy rice caused by artificial infestation by Sogatella furcifera (Horv.) in cages at levels between 15 and 200 insects per rice hill for different periods at different growth stages was measured. At the lowest population level of 15 insects per hill, 13–17% loss occurred after 60–120 days exposure at 15 d.a.t., 11–12% loss after 15–45 days exposure before tillering (42 d.a.t.), 18–37% loss after 15–60 days exposure at boot stage (62 d.a.t.) and 17–19% loss after 15–45 days exposure at earhead stage (104 d.a.t.). The benefit: cost ratios were all above 1, suggesting that both the economic injury levels and economic thresholds were at or below 15 insects per hill for these exposure periods at these growth stages of rice. Therefore, insecticide should be applied before populations reach the level of 15 insects per hill at any growth stage of the crop. |
