棉花叶螨的为害及防治指标研究

INVESTIGATIONS ON THE DAMAGE AND ECONOMIC THRESHOLDS OF SPIDER MITES TETRANYCHUS SPP.TO COTTON

棉花叶螨已成为河南省棉区的主要害虫。一般年份苗期、蕾花期、花铃期的红叶率每增加1％,产量损失率分别为0.119％、0.142％和0.284％,干旱严重的年份损失率分别为0.272％、0.406％和0.737％,根据防治棉花叶螨的投入和产出情况,制定了不同生育期的防治指标,即产量水平分别为50、75和100公斤的棉田的防治指标,在正常年份的红叶率(％),苗期分别为25、17和13;蕾花期为21、14和11;花铃期为11、7和5。严重干旱的年份较低。

Generally,every 1% red leaf rate of cotton increased in seedling,square-flower,and flower-boll stages damaged by cotton spider mitesTetranychus cinnabarinus and T.truncatus,one of the main cotton pest groupin Henan cotton area in recent years,caused 0.119%,0.142%,and0.284% of ginned cotton yield losses,respectively.The yield losseswere increased to 0.272%,0.407%,and 0.737%,respectively,in prolongeddrought condition. The action thresholds of cotton spider mites expressed as red leafrates in accordance with 50,75,and 100kg/mu yield levels were deter-mined as 25%,17%,and 13% in seedling stage,21% ,14%,and 11% in square-flower stage,and 11%,7%,and 5% in flower-boll stage,respectively. In droughty year,the action threshold should be limited morestrictly.