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豆天蛾以幼虫为害大豆叶子,初龄时咬食嫩叶边缘成孔洞,三龄以后把豆叶全部吃光,造成减产,甚至绝收。此虫一年发生一代,以老熟幼虫在三寸深的土层内越冬,豆田及附近田埂松土向阳的地方虫量最多,六月份化蛹,蛹期约十天左右,七月下旬为羽化盛期,成虫产卵五至七天,七月下旬至八月上旬为产卵、孵化盛期。八月上旬旬为幼虫盛发期,虫量大,为害重,进入九月份开始入土越冬。幼虫有避光及转株为害的习性,白天四龄前幼虫多躲在豆叶背面,五龄以后多在枝茎上柳息,以夜间为害最重,如迁两天则整天为害。成虫白天多隐避在玉米、谷子、高梁等生长茂密的作物叶子背面,傍晚活动取食花蜜。具有较强的飞翔力和趋光性。夜间
Bean budworm infestation of soybean leaves larvae, young leaves bite when the edge of the hole into the hole, after the third instar all the beans eat the edible leaves, resulting in reduced production, or even income. The worm occurs a generation a year to mature larvae in three-inch deep soil overwinter, soybean fields and near the field ripper sunny most pests, pupa pupation in June about ten days, in late July for Feathering period, the adult spawning five to seven days, late July to early August for spawning, incubation period. In early August, the larva was flourishing, with a large amount of pest and heavy pests, entering into the winter in September. The larvae have the habit of damp-proofing and transplanting their plants. During the daytime, the larvae in the fourth instar tend to hide behind the bean leaves. After the fifth instar, they mostly grow on the stems and willow, which will be hardest at night. Adult during the day and more to avoid the growth of corn, millet, sorghum and other leafy foliage on the back of the activity of feeding nectar in the evening. Has a strong flying force and phototropism. at night