一、大棚栽培的特殊环境导致病虫害发生严重大棚一经建成,便多年使用,加之规模经营,蔬菜品种单一,轮作困难,土壤中各种病原菌、寄生虫卵、盐分逐年积累,数量极大;大棚扣膜后,水分不易散失,空气湿度增高,昼夜温差大,使叶片吐水或结露,为传染性病害的发生与流行创造了有利条件。其二是在棚内复种指数高,病株残体不能及时清理,水、肥、气、温管理不合理,导致植株生长不健壮抗病性减弱。其三是在大棚蔬菜病虫害防治中,群众防治方法不科学,只注 First, the special circumstances of greenhouse cultivation led to pests and diseases led to a serious greenhouse once built, they use for many years, combined with the scale of operation, a single vegetable varieties, rotation difficulties, soil various pathogens, parasite eggs, salt accumulation year after year, a great number; Membrane, the water is not easy to lose, the air humidity increases, the temperature difference between day and night, so that spit water or condensation leaves, for the occurrence of infectious diseases and epidemic created favorable conditions. The second is that the mulching index is high in the shed, the diseased plants can not be cleaned up in time, and the unreasonable management of water, fertilizer, gas and temperature leads to the impaired plant growth and the weakened disease resistance. The third is in the greenhouse vegetable pest control, the masses prevention and control methods unscientific, only note