The diamondback moth (DBM), Plutella xylostella (L.) (Lep.: Plutellidae), is an important pest of broccoli (Brassica oleracea L. var. italica Plenck). Few studies have focused on the real DBM impact on broccoli yield. We performed greenhouse studies to assess the effect of DBM densities and infestation timing (at pre-heading, heading, or during the entire cycle) on broccoli head weight. Polynomial trend analysis revealed a downward linear response of head weight to DBM densities, indicating that broccoli is susceptible to DBM attack. As for the infestation timing, infestations during the pre-heading stage significantly impacted head weight, whereas the same did not occur for infestations during the heading stage. DBM density did not affect plant height or total leaves but was upward-related to plant defoliation, and head weight correlated negatively with plant defoliation. These findings indicate that pre-heading is the determining stage for head weight loss of plants under DBM attack. In order to prevent quantitative losses, efforts for DBM management should be focused on this particular stage.

小菜蛾 (DBM)，Plutella xylostella (L.) (Lep.: Plutellidae)，是西兰花 ( Brassica oleracea L. var. italica ) 的重要害虫普伦克）。很少有研究关注 DBM 对西兰花产量的实际影响。我们进行了温室研究，以评估 DBM 密度和侵染时间（在抽穗前、抽穗或整个周期期间）对西兰花头部重量的影响。多项式趋势分析显示头部重量对 DBM 密度呈下降线性响应，表明西兰花易受 DBM 攻击。至于侵染时间，抽穗前阶段的侵染显着影响了头重，而抽穗期的侵染则没有发生同样的影响。DBM 密度不影响植物高度或总叶数，但与植物落叶呈向上相关，而头重与植物落叶呈负相关。这些发现表明抽穗前是 DBM 攻击下植物头部重量损失的决定阶段。