Table 1.

A selected representative list of dieback-decline diseases chosen to represent a variety of hosts, predisposing stresses, organisms of secondary action and control.

AshAsh dieback, decline (general)1Fraxinus americanaF. pennsylvanicaDrought periodsBark canker fungi: Cytophoma pruinosa Fusicoccum sp.
  1. Reduced terminal and radial growth

  2. Death of terminal buds and branches

  3. Thin, “tufted” crowns

  4. Sometimes, early fall coloration

  5. Death of trees

  6. Reddish-brown to orangeyellow cankers on branches and stems

  1. Forest: little can be done, salvage

  2. Urban: water when feasible, possibly reduce water loss by mulching

Dieback (general, near coastal salt marshes with Spartina grass hostsFraxinus spp.Defoliation by rust fungus, Puccinia peridermiosporaNoneDieback occurs the season following severe defoliation/refoliation
  1. Death of terminal buds and branches

  2. Thin, “tufted” crowns

  3. Death of some trees

Most trees will recover unless defoliation is repeated or coincides with drought.
Beech Beech bark disease (general in east through NY and mid-PA; northeastern WV.) Fagus grandifolia F. syivaticaAttack by the beech scale, Cryptococcus fagisugaBark canker fungi: Nectria coccinea var. faginata; N. galligena
  1. Thinning chlorotic crowns

  2. Presence on bark, especially in roughened spots, of white “wool-like” wax of the beech scale

  3. Presence on bark previously infested by scale of small, red fruiting bodies of Nectria fungi

  4. Weeping exudates may precede or accompany the fruiting bodies

  5. Bark is killed, and trees die. Some trees snap off where bark dies and wood decays

  1. Forest: salvage trees when scale populations become high and Nectria is abundant. Trees free from scale (resistant) should be favored

  2. Urban: treat individual trees with dormant sprays or chemical fungicides registered for use against the beech scale

Dogwood Lower branch dieback, anthracnose (southern New England, northern midAtlantic states; urban, woodlands)Cornus florida, native and cultivarsSuspected: series of unusually wet springs, followed by summer dry periodsLeaf and twig fungus (Discula sp. Gnomonia sp.) of anthracnose type
  1. Blighted leaves in early spring

  2. Dieback of buds, twigs and branches beginning on lowermost parts of tree

  3. Development of branch cankers

  4. Water sprouts from near branch cankers — these in turn are killed, trees die

Not yet known
Maple Maple decline (general;forest) Acer saccharumDefoliation by a number of insects including:
  1. saddled prominent

  2. forest tent caterpillar

  3. maple webworm

  4. green stripped mapleworm

The shoestring root rot fungus, Armillaria mellea, and twig fungus, Stegonosporum sp.
  1. Death of buds, terminal twigs and branches the year after severe defoliation

  2. Thin “tufted” crowns

  3. New foliage on sprouts

  4. Continued decline and death of some trees

  5. White fungus “fans” often present beneath bark of roots and bases of dead and dying trees

  1. Forest: prevent defoliation, salvage if significant portion of crown is killed

  2. Urban: prevent defoliation

“Roadside” maple decline2 A. saccharumDeicing salts, and/or construction damage to rootsMany twig, root and stem decay fungi
  1. Crown dieback, especially on road side of tree

  2. Leaves show fall colors early and drop

  3. Leaves may also show inter- veinal necrosis (scorch)

  4. Dieback progresses over years, trees eventually die

  1. Avoid use of deicing salt when feasible

  2. Plant replacement trees where brine will not run over roots

“Urban” maple decline (Wisconsin) saccharumSuspect stress of planting trees too deeply in heavy soils, or settling of trees after plantingSoil borne canker fungi: Fusarium sp.; Phytophtho. citricola
  1. Leaves small, show fall colors early and drop

  2. Twigs and branches die back c) Rootlets die

  3. Bark at tree base loosens to show discoloration and decay of underlying wood

  4. Trees die one to several years after first symptoms

  1. Improve soil drainage

  2. Insure planting is shallow

Oak Oak decline (general) Quercus spp.Defoliation by any of several insects including:
  1. gypsy moth

  2. leaf rollers and tiers

  3. canker worms

  4. webworms, etc., and sometimes exacerbated by periods of water shortage

The shoestring root rot fungus, A. mellea; and the twolined chestnut borer, Agrilus bilineatus
  1. Dieback of terminal buds and branches in next season

  2. New foliage produced on sprouts in the crown and on the bole — crowns “tufted”

  3. Progressive dieback; mortality

  4. White fungus “fans” beneath bark (see Maple decline forest)

  5. “D”-shaped holes in bark and meandering insect galleries on outer sapwood beneath barka)

  1. Forest: prevent defoliation: salvage

  2. Urban: as above; supply water during refoliation if feasible. Possibly spray tree trunks to prevent attack by borers

Oak decline (midwest; urban)
  • Q. rubra

  • Q. alba

  • Q. macrocarpa

Adverse soil changes, including alkalinization, caused by various urban practices and disturbanceThe shoestring fungus, A. mellea, and the borer, A. bilineatus
  1. Deterioration of fine feeder root system

  2. Dieback and decline of upper crowns progressing sometimes until the tree dies

  3. Signs of A. mellea and A. bilineatus

Keep “wooded” areas as natural as possible; avoid watering with hard water, runoff from concrete surfaces, fertilizing with limebased fertilizers, mixing of soil by construction, grading, etc. Mulch and reduce grass competition
Oak decline (midwest; general)
  • Q. rubra

  • Q. Q. alba

Periods of unusual springtime wetness in areas where soil overlies dense claysThe shoestring fungus, A. mellea, and the borer, A. bilineatus
  1. Rapid dieback and decline of mature and overmature trees

  2. Signs of A. mellea and A.bilineatus

None known
Pin oak canker dieback3 (mid-Atlantic states; urban)
  • Q. palustris

Pruning wounds made during droughtBark canker fungus: Endothia gyrosa
  1. Dieback of lower branches, especially those from which smaller ones have been pruned

  2. Death of some trees

  3. Orange-red to brown-black fruiting pustules on dead bark

  1. Forest: not a problem

  2. Urban: water during drought periods. Avoid pruning during dry times.

  • 1. Ash trees are hosts also to several viruses and a mycoplasmalike organism (MLO). Evidence is mounting that the MLO can cause growth loss and mortality — and effects may be especially serious in times of drought. This disease is now known as ash yellows, or ash yellow decline.

  • 2. Both Na and Cl ions are cumulatively toxic to sugar maple. Heavy, repeated salt contamination can kill trees even in the absence of secondary organisms

  • 3. Endothia gyrosa also causes cankers and dieback associated with pruning wounds in American and Formosan sweetgum and in American beech. In this respect it is similar to the fungus Nectria cinnabarina, a pruning wound pathogen of many urban tree species that is especially serious during severe droughts.