Facilitation between invasive herbivores: hemlock woolly adelgid increases gypsy moth preference for and performance on eastern hemlock. (16th December 2019)

• Record Type: Journal Article
• Authors: Kinahan, Ian G.; Baranowski, Alex K.; Whitney, Elizabeth R.; Savage, Suzanne K.; Rigsby, Chad M.; Shoemaker, Emma E.; Orians, Colin M.; Preisser, Evan L.
• Is Part Of: Ecological entomology. Volume 45:Number 3(2020)
• Page Start: 416
• Page End: 422
• Publication Date: 2019-12-16
• Subjects: Adelges tsugae -- facilitation -- herbivores -- invasional meltdown -- Lymantria dispar; Insects -- Ecology -- Periodicals; Entomology -- Periodicals; 595.7
• DOI: 10.1111/een.12829
• Languages: English
• ISSNs: 0307-6946

Abstract

Abstract : 1. Interactions between invertebrate herbivores with different feeding modes are common on long‐lived woody plants. In cases where one herbivore facilitates the success of another, the consequences for their shared host plant may be severe. Eastern hemlock ( Tsuga canadensis ), a canopy‐dominant conifer native to the eastern U.S., is currently threatened with extirpation by the invasive stylet‐feeding hemlock woolly adelgid ( Adelges tsugae ). The effect of adelgid on invasive hemlock‐feeding folivores remains unknown. 2. This study evaluated the impact of feeding by hemlock woolly adelgid on gypsy moth ( Lymantria dispar ) larval preference for, and performance on, eastern hemlock. To assess preference, 245 field‐grown hemlocks were surveyed for gypsy moth herbivory damage and laboratory paired‐choice bioassays were conducted. To assess performance, gypsy moth larvae were reared to pupation on adelgid‐infested or uninfested hemlock foliage, and pupal weight, proportional weight gain, and larval period were analysed. 3. Adelgid‐infested hemlocks experienced more gypsy moth herbivory than did uninfested control trees, and laboratory tests confirmed that gypsy moth larvae preferentially feed on adelgid‐infested hemlock foliage. Gypsy moth larvae reared to pupation on adelgid‐infested foliage gained more weight than larvae reared on uninfested control foliage. 4. These results suggest that the synergistic effect of adelgid and gypsy moth poses an additional threat to eastern hemlock that may increase extirpation risk and ecological impact throughout most of its range. Abstract : Eastern hemlock ( Tsuga canadensis ) is threatened with extirpation by the invasive hemlock woolly adelgid ( Adelges tsugae ), an insect that may facilitate feeding by larvae of invasive gypsy moth ( Lymantria dispar ). Adelgid‐infested hemlocks experienced more herbivory than uninfested trees; larvae fed adelgid‐infested foliage pupated at higher weights. Another invasive herbivore, the elongate hemlock scale ( Fiorinia externa ), had no such impact. The synergistic effect of adelgid and gypsy moth poses an additional threat to eastern hemlock that may increase extirpation risk and ecological impact throughout most of its range.