Damage is characterized by the development of irregular areas of dead tissue on the leaves of the host. The fungus can spread to stems and twigs. Anthracnose fungi over winter on fallen affected leaves. Spores from these fallen leaves re-infect new leaves the following year.

Leaves infected by fire blight first appear water-soaked, then shrivel, turning dark brown or black as though scorched by fire. New infections may occur throughout the growing season during warm, humid weather, and are especially common after a summer hailstorm when bacteria are washed into wounds created by hail. 

Diseased areas should be sterile pruned. The pruners should be dipped in alcohol between cuts, and the cuts should be made 6 inches below the affected areas. 

Leaf spot diseases are first seen on the lower leaves and then develop or move up the plant. Young growth is most susceptible to the fungus. Common leaf spot produces small, circular brown or black areas on leaves. Infected leaves turn yellow and drop prematurely.

Cool, wet weather favors leaf spot development. It is found primarily in the spring, early summer, and fall. Fallen leaves from last season will re-infect new growth the next season.

Phomopsis blight mainly affects plants in poorly drained areas during periods of high humidity. Shaded plants are also more susceptible because due to extended periods of surface moisture.

The fungus infects needles and rapidly invades and girdles young stems. It can spread to older limbs and girdle them as well. All growth above the girdled area will die. Affected growth turns light green, then reddish brown, and finally ashen gray. The splashing effect of rainfall is the main way this fungus spreads throughout the plant. 

Powdery mildews appear as a dusty white to gray coating over leaf surfaces or other plant parts. It begins as small circular powdery white spots on the leaves. The fungus favors humid conditions, and dense growing or close-spaced plants are especially susceptible.  

Any affected fallen leaves should be removed over the winter to help avoid re-infection of new growth the following spring. Pruning to thin out plants and avoidance of planting too closely together will also help to minimize powdery mildew.

Newly planted trees and shrubs are often over-watered. Too much water suffocates and drowns roots. Root rot occurs when plants are over-watered, or when they are planted in areas that retain and hold too much water. Plants with root rot will begin to lose color, wither and wilt as if they are not getting enough water. The signs of stress are almost identical to those of drought stress or potbound roots. 

When roots affected by root rot are examined the roots are black, mushy, and they fall apart in your hands. There may be a swampy smell to the root ball as well. 

Allow the soil to drain and slightly dry out between waterings. Touch the soil around the base of the plant, and if the soil is moist, do not water it. 

Rust first appears on leaves as small orange to reddish-brown flecks. The disease spreads rapidly over leaf material, and can turn darker in color. Infected leaves turn yellow, wither and die.

Avoid over-watering and other forms of excessive moisture in order to help prevent rust. Proper annual fertilization will keep the nitrogen levels correct and will also help to reduce the appearance of this disease. 

Sooty mold looks like soot from a fireplace that has been deposited on leaf surfaces. It is a gray-black, velvety crust-like coating. The fungus does not actually feed on the leaves; it colonizes and feeds on a sticky, shiny excretion called "honeydew" that was previously deposited on the leaves by sucking insects such as aphids and whiteflies. Sooty mold does block sunlight from leaf surfaces, and thus can harm plants. Many people are allergic to sooty molds. 

The best way to control sooty mold is to control the insects that excrete the honeydew on the leaves. If these insects are controlled, there will be no honeydew for the sooty mold to colonize in and feed upon. 

New growth of needled evergreens is most susceptible to tip blight. The fungus spores are dispersed from infected tissue during rainy weather in the spring and summer. Infections begin at the base of new needles. Infected needles turn reddish-brown and die.

Conifers that are planted too closely together or planted in shady conditions are most susceptible to tip blight because there is not enough air circulation to allow the needles to remain dry during the day. Affected limbs should be pruned out as soon as damage is seen. This will help to minimize the spread of the disease to other parts of the plant.