Ash Management Guide for Private Forest Landowners

Wet Forest: Dieback and declineEmerald Ash Borer or Dieback-which is it?Many hardwood tree species haveexperienced periods of branch dieback,often called “decline.” Symptoms includeslow growth, thin crowns, and misshapenor discolored leaves. Characteristic of thesedecline episodes is that one single ‘cause’of the decline cannot easily be identified.Instead, evidence suggests that trees havebeen stressed and were then invaded by oneor more organisms that are not normallydamaging to those trees. Biotic agents suchas defoliating insects or abiotic factors suchas severe drought can predispose trees to anumber of pathogenic organisms that furtherdamage trees. However, not all affectedtrees will die. Once the stress is removed,many trees are able to regain normal vigorand growth.Dieback of black ash is an example ofa condition affecting trees in many areas ofthe Lake States and especially in northeastand north central Minnesota. For years,dieback, thin crowns, and in some stands –tree mortality have been observed. Addingto the appearance that this species isin decline is that black ash has a late leafflush and early leaf fall, therefore the treesseemingly never have full, vigorous crowns.In recent studies, it has been foundthat the most seriously affected trees werenearest to roads and on the wettest sites;even then, tree mortality was relativelylow. No causal agent was found affectingtrees with dieback, and on many treescrown recovery (multiple years of newbranch growth) was occurring.Distinguishing between the symptomsof decline or crown dieback and EAB isextremely difficult and critical.Landowners, especially those in thenorthern Wet Forest (WF) systems areencouraged to work with professional forestersto diagnosis, monitor, and carefullymanage these sites.Epicormic branching: Erratic growthfrom adventitious buds sprouting ontrunks of trees may indicate dieback. It’s acoin toss as to whether the tree is recoveringand beginning to rebuild its crown ordying. Epicormic branching may also bea symptom of a tree infested with emeraldash borer.Chapter 5The Native PlantCommunitiesWet Forest SystemGLOSSARYdieback/decline: The progressivedying from the extremity ofany part of a tree.abiotic: Nonliving parts of anecosystem, such as soilparticles, bedrock, air, andwater.leaf flush: The time in theseason during which leavesappear on a tree.crown dieback: Decline of thebranches and limbs in the canopyof a tree sometimes used asan indicator of tree health.adventitious: Pertaining toa plant part that developsoutside the usual order of time,position, or tissue — e.g., anadventitious bud arises fromany part of a stem, leaf, or rootbut lacks vascular connectionwith the pith; an adventitiousroot arises from parts of theplant other than a preexistingroot, e.g., from a stem or leaf.epicormic branching: A shootarising spontaneously froman adventitious or dormantbud on the stem or branch ofa woody plant often followingexposure to increased lightlevels or fire.Ash dieback in northernMinnesotaPhoto: Juile Miedtke35