Laboratory assessment of predation and fecundity of Laricobius species (Coleoptera: Derodontidae), predators of hemlock woolly adelgid

Abstract

ABSTRACT The hemlock woolly adelgid (HWA), Adelges tsugae (Hemiptera: Adelgidae), is native to the Pacific Northwest and Asia and is an invasive insect in the eastern United States causing widespread decline in health and increased mortality of native eastern and Carolina hemlock. Laboratory experiments conducted at ambient field temperatures were done to determine the adult and larval feeding totals on HWA and fecundity of the introduced predators Laricobius nigrinus and L. osakensis, and the native L. rubidus (Coleoptera: Derodontidae). During the 22-week period when Laricobius spp. adults are active in Virginia, from early November until late March the total mean ( x ¯ ± SE) of HWA eggs, nymphs, and adults were projected to be consumed per L. nigrinus (33.8 ± 4.0), L. osakensis (33.2 ± 4.0), and L. rubidus (16.4 ± 2.5) adults. Laricobius osakensis (102.1 ± 13.7) and L. nigrinus (72.0 ± 10.5), oviposited a similar number of eggs while L. rubidus (24.5 ± 5.2) oviposited a lower number of eggs. Mean larval consumption of HWA progrediens eggs was: L. nigrinus (169.6 ± 7.1), L. osakensis (140.1 ± 8.7), and L. rubidus (135.8 ± 12.8). The mean egg production of HWA was 74.5 ± 2.2. Based on predation and fecundity totals, L. osakensis was predicted to have a greater impact in reducing the number of HWA progrediens eggs than L. nigrinus and L. rubidus.