朝阳地区玉米螟为害损失调查及防治指标研究和探讨

CORN BORER DAMAGE INVESTIGATION AND ITS CONTROL THRESHOLD STUDY IN CHAOYANG AREA

根据１９９０～１９９３年调查研究和探讨，玉米螟为害玉米，随虫量增加，产量下降、千粒重降低。因玉米螟钻蛀造成玉米茎秆折断，下部折断比上部折断损失重，当百株玉米有玉米螟卵２２块时可成活玉米螟幼虫２０头，其造成的为害与上部茎秆因玉米螟为害２０株折断或下部茎秆６株折断，所造成的玉米产量损失相仿，都与防治所需费用相等。高于这个标准就应进行防治。

Based on the investigation in 1990～1993,the borer damaging the corn reduced 1000-gain weight and the yield which improved with the borer amount growing.As the borer cause the corn stalk broken down,the yield loss is usually higher caused by plants' lower part broken than by the upper part broken,when 22 pieces of borer eggs were found in 100 plants,20 borer larvae could live.As 20 plants' upper part broken or 6 plants' lower part broken cause the same yield loss ,and which are equal to the control costs,if thresholds exceed above value,control measures needed.