Aspen Shoot Blight (Venturia tremulae, V. populina): leaf spots and shoot death can plague regenerating stands of balsam poplar and aspen, shoot bends over in a 'shepard's crook' shape, leaves can turn dark brown or black, affects current year growth only, usually not a serious pest but can be quite noticeable at times

Ash Dieback (Candidatus Phytoplasma fraxini, Cytophoma pruinosa, Fusicoccum spp.): the cause is not fully understood but involves a fungus and a phytoplasm (kind of bacteria), weather is a significant factor, especially drought, symptoms similar to those of emerald ash borer infestations (top-down death, epicormic branching, stump shoots, etc.), crowns thin and form tufts

Beech Bark Disease (Nectria spp. + scale insect): a combination of insect and fungus, it's the Nectria fungi that typically kills the tree, introduced around 1890 but only within the last decade (or so) have killed much of the beech in Michigan, scales infest a tree and then introduce the Nectria which kills the tree, 'tar spots' are first indications of Nectria presence, often trees 'snap' at weak spots in the trunk caused by the fungus     

Black Knot of Cherry (Apiosporina morbosa): an easy to identify disease, forms black-crusty growths on twigs and branches, can appear like charcoal, sometimes reaches main stem, not usually fatal but can be unsightly to some people, some growths can become several feet long

Butternut Canker (Sirrococcus clavigignenti-juglandacearum): gradually killing much of the US butternut resource, tree species survival at risk, appears as crown loss and leaf clustering, epicormic branching (new sprouts from stems/branches), canker cracks eventually appear on stems and large branches, native vs. exotic debate, first noted in the 1960s

Dutch Elm Disease (Ceratocystis ulmi): a vascular disease that results in browning and leaf loss that might occur throughout a growing season and sometimes multiple growing seasons, it often begins with the yellowing of the leaves on a single branch (called flagging), transmission is via bark beetles (Scolytus multistriatus), usually trees must be 10+ inches in diameter, most large diameter elms have died, this loss is most noticable in residential areas where streets were once lined with large graceful elms     

Eutypella Canker (Eutypella parasitica): a common fungus in northern hardwoods, especially maple trees, introduced through a wound, thick callus growths result over time, sometimes swellings are large and oddly shaped, often follows sugar maple borer injury

Hickory Decline (Ceratocystis caryae, C. smalleyi): most of the UP hickory (mostly bitternut hickory) is located along the rivers and floodplains of Lake Michigan rivers, especially the Menominee River, the fungus causes long oval stains in the sapwood, often associated with a bark beetle (Scolytus quadrispinosus), severe spring drought stress in 2010 led to massive mortality from bark beetles and canker (to a lesser extent)

Hypoxylon Canker (Hypoxylon mammatum): a common disease of aspens, enters through wounds (Saperda beetles common wound-maker) cankers are sunken and colored a greenish-orange, older cankers have peeling bark and near black underneath, aspen often break at canker locations, severe infestations can kill entire stands

Oak Wilt (Ceratocystis fagacearum): biologically, oak wilt is a vascular disease that results in browning and leaf loss within a period of several weeks (which is considered quick), it can be mistaken for a leaf disease, leaves can brown & curl within 2-3 weeks at almost anytime during the growing season but more commonly occurs in the late spring / early summer, wilt begins at the tree top and works downward, trees in the red oak group commonly have root grafts that expedite disease spread, overland transmission occurs via sap-feeding beetles and probably a number of other vectors, avoid damaging/pruning oaks from May through August           

Sapstreak of Sugar Maple (Ceratocystis coerulescens): not common but it is fatal, infected tree produces small than normal leaves, gradual decline, crown begins to dieback, some Michigan locations identified

Trunks Rots: there are many fungal species that decay wood and eventually produce a conk (fruiting body), conks usually indicated an advanced state of internal decay (especially in aspen), many trunk rots are specific to particular tree species, some tree species can 'wall off' the rot and others cannot, trees cannot heal wounds and subsequent rot - they can only isolate and grow over them, some fruiting bodies are edible, artist conks are valuable in the craft industry        

      
[Trametes versicolor, Phellinus spp, (birch), Phellinus spp. (oak), Laetiporus sulfureus]

    
[Piptoporus spp., Ganoderma tsugae, Ganoderma applanatum]

Verticillium Wilt (Verticillium albo-atrum): a soil-borne fungus that moves through a trees vascular system, may affect only a portion of a tree or the entire tree, trees often recover if the infection is small and the tree is otherwise healthy, can occur at any time in growing season,

Hosts: many tree species but especially maples