连作晚稻三化螟为害损失与防治指标研究

A STUDY ON THE ACTION THRESHOLDS OF RICE YELLOW STEM BORER TO SUCCESSIVE CROPPING LATE RICE

三化螟幼虫在晚梗稻分蘖、圆秆、孕穗、破口期均能侵入,所形成的为害株数、为害类型和幼虫存活率与生育期有密切关系,为害丛、株增长呈S型曲线。分蘖期、孕穗—破口期引起丛、株为害率和损失率与卵块密度显著相关,每个卵块损失稻谷分别为59.11±2.99g、74.58±3.31g。考种结果表明,产量损失的主要原因是有效穗减少。在现有生产条件下,三化螟经济允许卵块密度为:分蘖期130—150块/666.7m^2,孕穗—破口期100—120块/666.7m^2;防治指标:分蘖期100—110块/666.7m^2,为害团50—60个/666.7m^2,丛为害率2.0％—3.0％,株为害率1.0％—1.5％。

The larvae of rice yellow stem borer(YSB)Scirpophaga incertulas(Walker) were capable to bore into the stems of late non-waxy rice in tillering-panicle initiation-booting-flowering stages. The damaged plant number and types and survival of larvae were closely related to the growth stages. The damaged hill and plant number increased with time like a sigmoid curve. The percentages of injured hills and plants,and yield losses were significantly correlated with the density of egg-mass. Each egg-mass deposited in tillering and booting-flowering stages caused 59. 11±2. 99g and 74. 58±3. 31g of yield losses, respectively, which were mainly resulted from the reduction of effective ears. Under recent condition of rice production, the tolerable economic injury levels in tillering and booting-flowering stages should be 130-150 and 100-120 egg masses per 666. 7 m2,respectively. The action thresholds in tillering stage were determined as 100-110 egg-masses or 50-60 damaged spots per 666- 7 m2,or 2% - 3% of damaged hills,or 1. 0% -1. 5% of damaged plants.