夏玉米苗期二点委夜蛾防治指标

为有效防治夏玉米苗期二点委夜蛾的为害,通过人工接虫方法研究了其幼虫虫口密度(x)与玉米缺苗率(y)的关系,采用人工去苗模拟为害方法研究了玉米缺苗率(y)与产量损失(z)的关系,并提出了夏玉米苗期二点委夜蛾的防治指标。结果显示,虫口密度为1、3头/株时,无缺苗现象,虫口密度为5、10、20和30头/株时,缺苗率分别为19.4%、22.8%、44.4%和49.6%。玉米缺苗率随着虫口密度增大而升高,二者呈显著二次线性相关:y=-0.0609x2+3.636x-4.5306,R2为9564;玉米缺苗率对单株穗重、穗长、穗粗和秃尖长等均无显著影响;玉米缺苗率(y)与产量损失(z)也呈二次线性相关:z=0.0036y2+0.3077y-0.3553,R2为0.9691。根据防治的直接收益和成本,提出夏玉米苗期二点委夜蛾幼虫的防治指标为3头/株,此时玉米缺苗率为6%~7%。

Economic threshold of Athetis lepigone at seedling stage of summer maize

In order to effectively control the damage of Athetis lepigone on summer maize, the relationship between A. lepigone larval density (x) and seedling missing rate (y) was evaluated by artificial inoculation method, and the relationship between maize seedling missing rate (y) and yield loss rate (z) was studied by pulling off maize seedlings to simulate the damage of A. lepigone larvae. The results showed that no maize seedling missing was observed at 1 and 3 larvae per plant, and seedling missing rates were 19.4%, 22.8%, 44.4% and 49.6% at 5, 10, 20 and 30 larvae per plant, respectively. The maize seedling missing rate increased with the density of A. lepigone larvae, which fitted with quadratic equation y=-0.0609x²+3.636x-4.5306 (R²=0.9564). Ear weight per plant, ear length, ear diameter and ear tip-barrenness were not significantly affected by the maize seedling missing rate. The relationship between maize seedling missing rate (y) and yield loss rate (z) was well simulated as follows z=0.0036y²+0.3077y-0.3553 (R²=0.9691). Based on the direct benefit and control cost, the economic threshold for controlling A. lepigone larvae were 3 larvae per plant or 6%~7% seedling missing rate.