Efficacy of neonicotinoid insecticidal seed treatments against Diceraeus melacanthus at different infestation times

Diceraeus melacanthus (Dallas, 1851) (Heteroptera: Pentatomidae) is one of the main early-season pests of corn in Brazil. The primary strategy for controlling this pest is using seed treatment (ST) with neonicotinoids. We aimed to determine seed treatment efficacy, damage reduction, and female fecundity at several infestation times. The trial was carried out in a greenhouse with ten replications in a 3x6 factorial design. The first factor consisted of ST (thiamethoxam, imidacloprid, and a control treatment), and the second factor of six infestation times (1, 3, 7, 10, 15, and 20 days after corn emergence (DAE)). Four adult stink bugs (two females and two males) were added to each pot containing two corn plants at each infestation time. We evaluated stink bug mortality at 1, 3, 5, and 7 DAE. Oviposition and damage to corn plants were determined seven days after infestation. Overall, thiamethoxam ST performed significantly better than imidacloprid. Seed treated with thiamethoxam and imidacloprid efficiently controlled the green-bellied stink bug and prevented crop damage up to 10 DAE. Female oviposition significantly increased when plants were infested at 15 and 20 DAE for thiamethoxam and imidacloprid ST (0-10% to 50-70%). Our results suggest corn seed treatment with neonicotinoids controls green-bellied stink bugs up to 7 DAE and infestations after 15 DAE increased female fecundity.