Abstract Early infestations of Diceraeus melacanthus in maize during vegetative stages can cause substantial economic loss. Currently, there are no objective decision-making criteria that can be used to manage the pest during these stages. Also, there is a lack of information regarding efficacy of insecticides registered to control the pest. Hence, the goal of this study was to estimate decision-making indexes for D. melacanthus infesting maize during different vegetative periods (VE-V2, VE-V4 and VE-V6) and to evaluate if insecticides registered for seed treatment and foliar application avoid economic loss caused by the pest. Trials with varying insect densities (0, 3, 6, 12 and 24 insects per plot) were performed, where damage rating and yield were measured. These estimations, together with the control cost and production value, were used to calculate economic injury levels (EILs) and economic thresholds (ETs) based on the number of insects and damage rating. We also tested insecticides recommended for seed treatment and foliar application, and analyzed their residues in selected scenarios. Economic thresholds for D. melacanthus infesting maize during vegetative stages should be based on the number of insects found on the plants, as damage rating-based thresholds are so low as to be difficult to determine. Economic thresholds are 3–46 insect 100 plants−1, depending on the stage of the plants and maize market value. Decision-making to control D. melacanthus, disregarding market value, should occur when 1.4, 0.5 and 0.2 adult row m−1 is found infesting maize in VE-V2, VE-V4 and VE-V6, respectively. Insecticides registered for foliar application and seed treatment do not prevent economic loss caused by the pest. This is likely the result of a significant reduction in insecticide concentrations (up to 440x) after only 14 days post-treatment. Hence, other effective D. melacanthus management methods should be explored.

中文翻译：

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营养玉米中黑角螟（半翅目：五足科）的经济伤害水平和经济阈值。

摘要 玉米营养期黑麦草属的早期侵染会造成巨大的经济损失。目前，没有客观的决策标准可用于在这些阶段管理有害生物。此外，缺乏关于已登记的用于控制害虫的杀虫剂的功效的信息。因此，本研究的目的是估计不同营养时期（VE-V2、VE-V4 和 VE-V6）侵染玉米的 D. melacanthus 的决策指标，并评估注册用于种子处理和叶面施用的杀虫剂是否避免害虫造成的经济损失。进行了具有不同昆虫密度（每个地块 0、3、6、12 和 24 只昆虫）的试验，并测量了损害等级和产量。这些估计，连同控制成本和产值，用于根据昆虫数量和损害等级计算经济伤害水平 (EIL) 和经济阈值 (ET)。我们还测试了推荐用于种子处理和叶面施用的杀虫剂，并分析了它们在选定场景中的残留量。D. melacanthus 在营养阶段侵染玉米的经济阈值应基于植物上发现的昆虫数量，因为基于损害等级的阈值低到难以确定。经济门槛是 3-46 昆虫 100 株-1，这取决于植物的阶段和玉米市场价值。当在 VE-V2、VE-V4 和 VE-V6 中分别发现 1.4、0.5 和 0.2 个成虫行 m-1 侵染玉米时，应做出控制 D. melacanthus 的决策，而不考虑市场价值。注册用于叶面施用和种子处理的杀虫剂并不能防止有害生物造成的经济损失。这可能是因为在处理后仅 14 天杀虫剂浓度显着降低（高达 440 倍）。因此，应探索其他有效的 D. melacanthus 管理方法。