小菜蛾危害引起的秋花菜产量损失及其防治指标研究

Studies on the Influence of Diamond-back Moth on the Yield of Autumn Cauliflower and the Economic Thresholds

利用笼罩接虫的方法,测定了秋花菜不同生育期小菜蛾幼虫数量与产量损失率(%)的关系。结果表明,在花菜的还苗期、莲座期、球花始期、球花中后期,随着接入虫数的增加,花菜产量均逐渐下降。还苗期、莲座期、球花始期和球花中后期小菜蛾幼虫的数量(X)与产量损失率(Y)的关系分别为:Y=-0.7969+1.0880X+2.0234X2、Y=-2.4489+7.4585X-0.2433X2、Y=-1.4557+7.6682X-0.2470X2、Y=0.8668-0.3096X+0.0905X2。花菜在不同的生育阶段对小菜蛾危害的敏感性不同,以球花初期最为敏感,其次为莲座期和还苗期。在球花初期,低虫量的小菜蛾就可能引起花菜产量明显的损失,因而此期的防治最为关键。当球花初期单株虫量达到0.5～1头,球花中后期单株虫量达到4～6头时需要进行防治。

The yield loss caused by the diamond-back moth (Plutella xylostella) at the different growth stages of autumn cauliflower was studied in a caged condition. The results showed that the yield loss increased with the number of inoculated diamond-back moth larvae increasing. The quantitative relations between the percentage of yield loss (Y) and the number of diamond-back moth larvae per plant (X) at the seedling stage after field planting, rosette stage, initial heading stage and mid-late heading stage could be expressed respectively by Y=-0.7969+1.0880X+2.0234X^2,Y=-2.4489+7.4585X-0.2433X^2,Y=-1.4557+7.6682X-0.2470X^2 and Y=0.8668-0.3096X+0.0905X^2. The sensitivity of cauliflower to diamond-back moth damage was significantly different at different growth stages. The initial heading stage was the most sensitive one and next was the rosette stage. Thus, the initial heading stage was a critical one to control diamond-back moth on cauliflower. It is suggested that diamond-back moth larvae should be controlled when their density reaches 0.5～1.0 head/plant at the initial heading stage or 4～6 heads/plant at the mid-late heading stage.