小麦收获期对麦套棉田捕食性天敌和棉花苗蚜的影响

2004-2005年在冀南棉区研究了小麦收获期对麦套棉田中捕食性天敌和棉花苗蚜的影响。小麦收获期共设3个水平,分别是6月5日、6月10日和6月15日收获小麦。结果表明:2004年3个时期收获小麦对棉田的益害比(天敌和棉蚜的比值)无显著影响(t>0.05);2005年6月5日收获小麦,显著增加了棉田的益害比(t<0.05),6月10日和6月15日收获小麦对棉田的益害比无显著影响(t>0.05)。说明在麦套棉田中,麦田天敌到棉田的有效转移受麦蚜-天敌-棉蚜三者发生高峰期的影响,不同年份天敌的转移情况有所不同。麦蚜发生高峰期早则小麦天敌向棉田转移早,并能有效控制苗期蚜虫的危害,在麦熟期收获小麦,对棉田天敌的数量影响不大;反之,若麦蚜发生高峰期晚,麦田天敌发生期也会相应延后,在麦熟期收获小麦则会引起棉田天敌的增加。因此,棉田天敌数量变化受小麦收获期的影响,但与麦蚜和麦田天敌的发生动态有直接关系。

Effects of Different Wheat-cutting Dates on Predators and Cotton Seedling Aphids in Wheat-cotton Intercropping Field

Systematic studies were conducted on predators and cotton seedling aphids in wheat-cotton intercropping field in North China in 2004-2005.Three treatments of wheat-cutting dates were designed on 5 June,10 June and 15 June respectively to investigate the influence of wheat-cutting dates on predators and cotton seedling aphids.The results showed that there was no significant difference in predator/cotton aphid ratio between treatment field and control field during different wheat-cutting dates in 2004(t>0.05).A significant difference was observed in predators/cotton aphids between treatment field and control field on 5 June in 2005(t<0.05),but no significant difference was found in other wheat-cutting dates in 2005(t>0.05).Wheat-cutting could obviously increase predator populations into cotton.The results suggested that the peak time of wheat aphids,predators and cotton aphids determined the efficient movement of predators from wheat field into cotton field.The earlier peak day of wheat aphids made it possible that predators move into cotton field earlier,and predators can effectively suppressed cotton seedling aphids.Thus,few predators increased in cotton during wheat-cutting period.The later peak day of wheat aphids delayed the movement time of predators from wheat field into cotton field,and cotton predators increased obviously when wheat is harvested during wheat maturation period.The occurrence dynamic of predators and cotton seedling aphids in cotton fields were affected by wheat-cutting dates,but it was directly related to the occurrence of wheat aphids and predators in wheat.