连作晚稻三化螟为害损失与防治指标研究

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％。

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

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±2.99 g and 74.58±3.31 g 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.