Parasitoids and pathogens in a collapsing <i>Lymantria dispar</i> (Lepidoptera: Erebidae) population in Lower Austria

A local population outbreak of the spongy moth, Lymantria dispar L. (Lepidoptera: Erebidae), in Lower Austria, resulted defoliation an oak forest 2018 and 2019. In study year 2020, density was still high but expected to decline. present work, role parasitoids pathogens collapse investigated. total, 20 egg masses, 680 larvae 12 pupae were collected field from April July 2020 reared until emergence adult moths or death. Causes mortality determined based on emerging microscope inspection non-parasitized cadavers. Stage-specific rates calculated for eggs, larval stages (L1–L6) pupae. Seven parasitoid species three responsible premature death moths. The Anastatus disparis (Hymenoptera: Eupelmidae) emerged 19% all eggs. Larval caused stage-specific 15% 61%. dominant young intermediate instars solitary wasp Glyptapanteles porthetriae Braconidae). Mature mainly parasitized by parasitic flies Blepharipa pratensis (Diptera: Tachinidae) Parasetigena silvestris Tachinidae). Pathogens 11% 41%. nuclear polyhedrosis virus (LdNPV; Lefavirales: Baculoviridae) pathogen instars. introduced fungus Entomophaga maimaiga (Entomophthorales: Entomopthoraceae)—detected first time Austria 2019—caused low older larvae. Starting mass densities spring, moth declined negligible levels summer.