Candidate natural enemy assemblage for biological control of Lymantria dispar L. in oak (Quercus spp.) with different levels of pest infestation

Abstract

Mediterranean Quercus forests have great ecological importance but face numerous threats, including pests. The spongy moth, Lymantria dispar L., is a major oak defoliator across its geographical range and has a natural enemy complex that may control its population dynamics. This study aimed to investigate candidate predators (Coleoptera: Carabidae) and parasitoids (Hymenoptera: Encyrtidae, Ichneumonidae, Pteromalidae, Braconidae, Bethylidae, Ceraphronidae, Eulophidae, Eupelmidae and Trichogrammatidae; and Diptera: Tachinidae), for the control of L. dispar in two areas in Andalusia (Spain). We studied 10 Quercus stands (Q. suber, Q. ilex, and Q. pyrenaica), with different L. dispar infestation level. Insects were collected using pitfall and cross-vane traps, during the defoliator's larval period. Four genera comprised 92.2% of all the Carabidae predators found: Steropus Dejean (34.1%), Carabus L. (28.4%), Calathus Bonelli (15.9%), and Platyderus Stephens (13.8%); and four Hymenoptera families comprised 93.7% of the parasitoid specimens collected: Encyrtidae (61%), Ichneumonidae (17.5%), Pteromalidae (10.7%), and Braconidae (4.5%). Both the natural enemy assemblage composition and the abundance per tree varied between geographical areas, as well as between levels of defoliator infestation. The candidate enemy complex was markedly diverse and abundant in stands not infested by L. dispar, where no insecticides had been applied. Our results suggest the importance of generalist predators as natural enemies of L. dispar.