Synchrony of larval parasitoids of the emerald ash borer with susceptible stages

Ever since its discovery in Michigan in 2002, the invasive pest emerald ash borer (EAB) (Agrilus planipennis Fairmaire) has killed hundreds of millions of ash trees. Classical biological control through the release of introduced parasitoids is the most promising means to impact EAB at this large scale. However, little research documents EAB phenology alongside its larval parasitoids in the field. The objective of this study was to measure the phenology of EAB, which is susceptible to parasitism as L3/L4 larvae, and its larval parasitoids at two field sites in Maryland. Monthly from May through November 2022, we sampled EAB stages by debarking infested ash trees, and semi-monthly used yellow sticky cards and sentinel logs with susceptible larvae to verify the presence and activity of parasitoids. We found that adults of wasps started foraging and attacking EAB in May, however, L3/L4 susceptible larvae were not present until later in the season. These results will be useful towards fine-tuning the optimal release timing of EAB biological control agents.