Tree responses to an invasive sap-feeding insect

Abstract

14Although sap-feeding insects are known to negatively affect plant growth and physiology, less is 15 known about sap-feeding insects on woody plants. Adelges tsugae (Annand Hemiptera: 16 Adelgidae), the hemlock woolly adelgid, is an invasive sap-feeding insect in eastern North 17America that feeds on and kills Tsuga canadensis (L. Carrière), eastern hemlock. In the summer, 18 newly hatched nymphs crawl to young unattacked tissue, settle and immediately enter diapause 19 (aestivation) while attached to hemlock. We assessed the effect of A. tsugae infestation on T.

Senescence‐feeders: a new trophic sub‐guild of insect herbivores

“…; Gonda‐King et al. ). It seems to be counter‐productive for a sap sucker to inject toxins that injure or kill the plant from which it is drawing its food.…”

Individual and non‐additive effects of exotic sap‐feeders on root functional and mycorrhizal traits of a shared conifer host

“…Moreover, it has been hypothesised that hemlock mortality following HWA attack may be due to hydraulic failure (Domec et al., ). Numerous lines of evidence support this hypothesis, including HWA‐induced formation of abnormal wood (Gonda‐King, Radville, & Preisser, ) and reductions in stomatal conductance (Gonda‐King et al., ). Branches from HWA‐infested trees have upwards of 50% more false rings, layers of thick‐walled xylem cells that can significantly restrict water flow (Spicer & Gartner, ), than uninfested trees (Gonda‐King et al., ).…”

“…First, trees attacked by HWA exhibit root traits that can limit their foraging ability. Given HWA reduction in photosynthesis and carbon assimilation (Gonda‐King et al., ), we expect root production and maintenance to be limited. HWA‐infested trees may produce thinner roots to maximise water and nutrient uptake while reducing carbon costs.…”

“…Eastern hemlock, a member of the Pinaceae family, interacts symbiotically with EMF, which form dense hyphal sheathing around its roots and heavily mediate water and nutrient uptake (Smith & Read, ). As with root production and maintenance, we expect that HWA‐infested trees will be limited in their ability to support EMF associates through carbon provisioning due to reduced photosynthesis (Gonda‐King et al., ). Overall, considering that EHS generally weakens rather than kills hemlock, we expect to observe only a small negative effect of EHS on root functional traits, including shifts in nutrient allocation from below‐ to above‐ground, as well as EMF colonisation.…”

Influence of Hemlock Woolly Adelgid Infestation Levels on Water Stress in Eastern Hemlocks within the Great Smoky Mountains National Park, U.S.A.

“…Although imidacloprid treatment can reduce tree mortality, its effectiveness is influenced by several factors, including tree water stress [2]. Adelgid infestation has recently been found to influence tree water relations in mature stands [2] and saplings [3] but this relationship between water stress and infestation rates is basically unknown, and an understanding of these could greatly increase the efficiency of management for this invasive insect. Two species of hemlock, eastern hemlock, Tsuga canadensis (L.) Carrière, and Carolina hemlock, Tsuga caroliniana Engelmann, are found in the eastern United States.…”