Common name: Fire blight

Causal organism: Erwinia amylovora 

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Common name: Crown gall

Causal organism: Agrobacterium tumefaciens

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Common name: Apple mosaic virus

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Common name: Ash yellows

Causal organism: Unidentified mycoplasma-like organism

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Common name: Leafy mistletoe

Causal organism: Phoradendron sp.

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Common name: Leafy mistletoe

Causal organism: Phoradendron juniperinum

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Common name: Eastern dwarf mistletoe

Causal organism: Arceuthobium pusillum 

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Common name: Southwestern dwarf mistletoe 

Causal organism: Arceuthobium vaginatum

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Common name: Lodgepole pine dwarf mistletoe 

Causal organism: Arceuthobium americanum

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Common name: Beech drops

Causal organism: Epifagus virginiana 

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Common name: Indian pipe

Causal organism: Monotropa uniflora

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Common name: Epiphytic plant

Epiphytes are not parasitic. 

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Common name: Leaf scorch

Causal agent: Hot weather and drying winds, combined with excess salt, pavement or drought which can result in water shortage for the host. The leaves lose more water through transpiration than the tree can take up. 

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Common name: Winter burn or winter browning

Causal agent: In winter, a sudden drop in temperature at sunrise or sunset on the southside of evergreen trees where host tissue is exposed to sun and becomes active. The rapid cooling injures activated foliage.

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Common name: Frost injury

Causal agent: Late spring or early fall frost when tree foliage is succulent and actively growing. 

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Common name: Frost crack 

Causal agent: A sudden drop in winter temperature causes the outer cells of the wood to contract faster than the inner cells. 

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Common name: Salt damage

Causal agent: Ocean salt spray or road salt, usually sodium chloride (NaCl). 

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Common name: Air pollution injury or Ozone damage

Causal agent: Ozone (O³) generated in polluted air by ultraviolet radiation and oxides or oxygen. It builds up to toxic levels for plants in urban areas during warm sunny weather.