Economic injury levels and economic thresholds for Diceraeus (Dichelops) melacanthus (Hemiptera: Pentatomidae) in vegetative maize

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. [Display omitted] •Decision-making should be based on the number of D. melacanthus per corn plant.•Decision-making should occur when 0.03 to 0.46 adult plant−1 is found.•High market corn prices produce ET's 50% less than low market corn prices.•Seed treatment or foliar sprays do not prevent D. melacanthus from reaching ET.•Neonicotinoids alone or with pyretroids do not offer efficient pest control.