All Fact Sheets
Armillaria root rot, sometimes called shoestring root rot, is caused by various species of the fungus Armillaria. Susceptible plants include most deciduous and coniferous species.
Leaf scorch, sometimes called marginal leaf burn, describes the death of tissue along the edge of the leaf. This symptom develops when sufficient water does not reach the leaf margin cells.
Many mature trees, including elms, oak, tulip poplar, and maple, exhibit large light or dark vertical streaks on their trunks resulting from slimy liquid oozing out of crack or wounds and running down the bark. This is called 'slime flux'.
The fungus Plowrightia morbosa (Apiosporina) causes the formation of dark brown to black, long, swollen galls or knots on the branches of most types of cultivated plums, prunes and cherries.
The fungus Botryosphaeria can cause a branch dieback on horsechestnut, redbud, dogwood, beech, walnut, tulip poplar, sweetgum, crabapple, pine, oak, rhododendron, azalea, rose, willow, elm, yew, and many other woody ornamentals.
Localized areas of dead bark and underlying wood on twigs, branches and trunks are called cankers.
London plane and sycamore trees are susceptible to a fungus, Ceratocystis fimbriata f. sp. platani, that is lethal. The living cells of the wood in the phloem, cambium and sapwood are invaded quickly soon after a fresh wound exposes those cells.
Cedar-apple rust and closely related diseases, cedar-quince, cedar-hawthorn, and Japanese apple rusts are caused by fungi belonging to the genus Gymnosporangium.
Crown gall is caused by bacteria belonging to the genus and species Agrobacterium tumefaciens. This bacterium can infect a wide range of herbaceous and woody plants.
Blue and Norway spruces are susceptible to a branch killing disease caused by the fungus Cytospora kunzei.
Root death is an important cause of poor plant health in woody plants. When roots are killed, the plant is not able to take up sufficient water or nutrients to support the development of branches, leaves, flowers, or fruit.
The fungus Eutypella parasitica kills the growing layer of cells under the bark, the cambium, and causes a pronounced bulge of callus to develop around the infected area of red, sugar, silver, Norway, and other maples.
Fire blight is a disease caused by the bacterium Erwinia amylovora. This bacterium can attack more than 75 species of trees and shrubs including apple, pear, quince, mountain ash, crabapple, hawthorn, cotoneaster, serviceberry, and pyracantha.
Most plant diseases cause a loss of yield or damage the aesthetic qualities of the infected plant. Certain diseases of trees, however, weaken their structure and create a hazardous situation where property damage or serious bodily injury could result from falling limbs or the toppling of the entire tree.
Some devastating pathogens in woody ornamentals are moved from plant to plant or 'vectored' by insects.
A tree presents a hazard if a defective part poses a high risk, upon its structural failure, to cause personal injury or property damage.
Junipers (Juniperus sp.), also known as red cedars are susceptible to a disease that results in the death of twig tips.
The fungus Nectria invades wood damaged by freezing, hail, animals and insects.
Nematodes are soil-dwelling non-segmented roundworms, usually less than 0.5 mm (0.02 in.) long.
Oak leaf blister, caused by the fungus Taphrina caerulescens, occurs on most species of oaks.
Oak wilt occurs west of the Susquehanna River in Pennsylvania.
Fungus-like organisms belonging to the genus Phytophthora are soil- or plant-borne and all are plant pathogens.
Plum pox is a serious disease of Prunus species caused by a virus.
The bacterium Pseudomonas syringae, is an opportunistic pathogen that can attack a wide variety of woody plants especially when they are damaged by frost or injured in some way.
A common disease of roses called black spot is caused by the fungus Diplocarpon rosae. This fungus readily attacks young expanding leaves and young canes.
The scheduling of effective disease management measures is not a simple task nor can it be standardized. The activities of the organisms that cause plant diseases are not governed by the clock or the calendar. Their activity is influenced by temperature, relative humidity, soil moisture and other highly changeable environmental factors.
Austrian, Scots, ponderosa, mugho, red and other 2 and 3-needled pines are susceptible to the killing of shoot tips and branches caused by the fungus Diplodia pinea (formerly Sphaeropsis sapinea).
Most deciduous trees and many shrubs are susceptible to a disease called Verticillium wilt caused by the fungus Verticillium. Conifers do not appear to be susceptible.
Selecting annuals and perennials for placement in the landscape as well as monitoring them for diseases and planning appropriate disease management strategies can be simplified if the key plants are known and if the key pathogens on those plants can be identified.
Note the black fruiting structures on the curved part of this tip.