小麦开花灌浆初期喷施农药对灌浆后期灰飞虱的影响及生化分析

Effects of Spraying Pesticides at Early Flowering or Grain Filling Stages on Small Brown Planthoppers During Wheat Filling Period and Relevant Biochemical Analysis

为明确麦田常规使用农药对灌浆后期灰飞虱虫量的影响并揭示原因,为稻麦病虫害的综合治理提供理论依据,通过大田试验,开花初期喷施杀菌剂,花后7d喷施杀虫剂,研究了小麦花后5种农药(杀菌剂:多菌灵、咪鲜胺;杀虫剂:毒死蜱、乐果和吡虫啉)对小麦灌浆后期灰飞虱的影响。结果表明,施用多菌灵、毒死蜱和乐果均能导致小麦灌浆后期灰飞虱虫口密度显著增加,其中毒死蜱和毒死蜱加多菌灵处理分别使虫量增加255.2%和425.6%。花后27d测定小麦叶、穗中的游离氨基酸、还原糖、酚含量和蔗糖转化酶(Invertase,Inv)、多酚氧化酶(Polyphenol oxidase,PPO)活性,结果显示,与对照相比,除吡虫啉和咪鲜胺外的农药处理均使小麦叶、穗中的游离氨基酸、还原糖含量和Inv活性增加,酚含量和PPO活性降低,以多菌灵加毒死蜱处理的调控效应最大。经相关分析,麦田灰飞虱虫口密度与小麦叶、穗中游离氨基酸含量、还原糖含量和Inv活性呈正相关,与小麦叶中酚含量和PPO活性呈负相关,说明农药对灰飞虱虫量的影响,可能是由于农药使小麦植株生理生化发生变化而引起。把灰飞虱虫量作为重要考虑因素,建议防治小麦赤霉病时宜轮换使用多菌灵与咪鲜胺,防治麦蚜时宜选用吡虫啉。

In order to understand the effect and mechanism of pesticides used at early flowering or grain filling stages on small brown planthoppers during late grain filling period and to provide guidance for integrated control techniques of pests and diseases in wheat and flee, a field experiment was conducted to study the effects of five pesticides （fungicides： earbendazim and proehloraz; insecticides： ehlorpyrifos, dimethoate and imidaeloprid） on the numbers of small brown planthoppers during late grain filling period in wheat. Fungicides were sprayed at early anthesis and insecticides spayed on the 7th day after anthesis. The results showed that earbendazim, ehlorpyrifos and dimethoate all caused the increment of the numbers of small brown planthoppers after treatment. The numbers of small brown planthoppers in plots treated with ehlorpyrifos or ehlorpyrifos and earbendazim were 255.2% or 425.6% higher than that in the control plot respectively. Free amino acid, deoxidized sugar, total phenolic content, invertase （Inv.）, polyphenol oxidase （PPO） activity in leaves and ears of wheat were investigated on the 27th day after anthesis. Compared with the control, all pesticide treatments except for imidaeloprid and proehloraz caused the increment of free amino acid, deoxidized sugar content and Inv activity, and decrease of total phenolic content and PPO activity in leaves and ears in wheat, among which ehlorpyrifos plus earbendazim treatment was the most apparent. The numbers of small brown planthoppers were positively correlated to free amino acid, deoxidized sugar content and Inv activity in leaves and ears in wheat, and negatively correlated to total phenolic content and PPO activity in leaves in wheat, suggesting that the influence of pesticides on the small brown planthoppers might be due to the physiological and biochemical changes of wheat plant. Taken the number of small brown planthoppers into consideration, earbendazim and proehloraz should be applied alternately to control wheat scab, and imidaeloprid be applied to control wheat aphids