Abstract
Although sap-feeding insects are known to negatively affect plant growth and physiology, less is known about sap-feeding insects on woody plants. Adelges tsugae (Annand Hemiptera: Adelgidae), the hemlock woolly adelgid, is an invasive sap-feeding insect in eastern North America that feeds on and kills Tsuga canadensis (L. Carriere), eastern hemlock. Newly hatched adelgid nymphs crawl to young unattacked tissue, settle and immediately enter diapause (aestivation) while attached to hemlock in summer. We assessed the effect of A. tsugae infestation on T. canadensis growth and physiology by analyzing hemlock growth on lateral and terminal branches, water potential, photosynthesis, stomatal conductance, and foliar nitrogen (%N). A. tsugae infestation greatly decreased terminal and lateral growth of eastern hemlock. In addition, A. tsugae presence reduced photosynthesis by 10 % in September and 36 % in October. Adelgid-infested hemlocks also exhibited signs of water stress that included notable reductions in water potential and stomatal conductance. These responses shed light on possible mechanisms of adelgid-induced mortality.
Highlights
Sap-feeders often have long-lasting physiological impacts on their host plant
We found that A. tsugae had significant impacts on hemlock growth
By the end of the growing season, terminal branches on control trees were 41% longer and had 56% more new buds than A. tsugae-infested trees
Summary
Sap-feeders often have long-lasting physiological impacts on their host plant. These physiological changes are driven by both changes in plant nutrients (Masters & Brown 1992; McClure 1980) and the production of secondary chemicals (Haukioja et al 1990; Karban &Myers 1989). Conifers may be especially susceptible to sap-feeders because they allocate more storage compounds to foliage as opposed to deciduous trees that store resources in their roots, stems, and other tissues inaccessible to sap feeders (Chapin et al 1990; Hester et al 2004; Krause & Raffa 1996b). The lack of such stored resources may make conifers more likely to succumb to intense sap-feeding events (Fernandes 1990; Furuta & Aloo 1994; Paine 2000). Adelges tsugae feed by inserting their stylet bundle at the base of a needle into the ray parenchyma tissue (Young et al 1995) and can kill mature hemlocks within four years of infestation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
