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Heart Rot

(On crabapple in front of Kilgore Hall, on maple and water oak in front of D.H. Hill Library and numerous other trees throughout the campus)

Heart rot of living trees destroys a greater volume of wood than all other tree diseases put together. It is equally important in both hardwoods and conifers.

Heart rot is not limited to one area of a tree. It occurs both in upper and lower regions of trees, better classified as top rot and root and butt rot. Heart rot refers to the decay of the heartwood of a living tree.

Heart rot is caused by a variety of species of wood decay fungi. It is impossible to determine the species of fungus responsible for heart rot of a specific tree without a reproductive body of the fungus. The heart rot of the crabapple pictured in Fig. 1 is caused by Panus strigosus (Fig. 2) , a fungus that produces mushrooms only in late summer and fall.
 

Fig. 1

Fig. 2

Common infection courts for wood decay fungi include broken branches, fire scars, and mechanical wounds from logging, pruning, and various machines. In Fig. 3 note the decayed area where a limb was pruned. This is a very common site for wood decay fungi to enter.	Fig. 3
Fig. 4 shows the basidiocarp of the root and butt rot fungus Inonotus dryadeus. This wood-decay fungus forms a basidiocarp that persists for more than one year. The bright yellow coloring, however, quickly weathers to a dull brown. This massive basidiocarp can be seen at the base of the water oak at the front of D.H. Hill Library.	Fig. 4
Pathological rotation is one of the most important management techniques. Trees are harvested at an age before losses due to decay become economically important. Other control methods include reducing the number of infection courts by controlling wild fires and maintaining more careful logging operations.

Go to PP318 Disease Profile of Wood Decay
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This profile was written by Becky Bernard

It was last updated on May 5, 2000

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Fusiform Rust of Southern Pines

(Found on loblolly pines located between railroad tracks and Dan Allen parking deck.)

Fusiform rust of southern pines is considered the single most important disease of conifers, occurring both in the field and in the nursery. It results in millions of dollars of damage each year in the southern United States.  Fusiform Rust is caused by the rust fungus Cronartium quercuum f. sp. fusiforme. The primary hosts of fusiform rust are young loblolly and slash pines. Generally, the trees are resistant by the time they are 15 years old. Several species of oak serve as the alternate host for this fungus. Red oaks are notably more susceptible to infection than white oaks.

Symptoms of fusiform rust include a large fusiform-shaped gall on the trunk or branches of the tree, as shown in Figs. 1 and 2. This gall tissue may die, forming a canker (Fig. 2). Also, newly infected needles become necrotic. Although trees often continue their growth after infection, mortality of the tree may eventually result. A sign of the disease is shown in Figs. 1 and 3. Aecia, a reproductive structure of the rust fungi, appear as orange blisters on the surface of the gall in the spring of the year following successful fertilization. The aeciospores are then wind disseminated to young oak leaves (the alternate host plant) to continue the disease cycle.

There are various methods of control for fusiform rust. If branch galls are more than 12 inches away from the trunk, pruning would be effective. Fungicides can also be used if economically feasible, especially in nurseries. Prescribed burning to remove susceptible oak species, and selection of resistant loblolly and slash pine families are also effective methods of control.

Fig. 1

Fig. 2

Fig. 3

 

Go to the PP 318 Plant Disease Profile of fusiform rust
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This profile was written by Becky Bernard

It was last updated on May 5, 2000

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Leaf Spot on Kalmia latifolia

(located at the east entrance to Kilgore Hall)

Most species of deciduous plants are subject to a variety of leaf spots. These spots represent dead areas in the leaf tissue. If the infection is severe, leaf fall is ultimately the result.	Leaf spot on Kalmia latifolia	Leaf spots, leaf blotch and anthracnose are just a few of the common names given to leaf diseases of trees and other woody plants. They are caused by a variety of different fungi most of which are characterized by forming a reproductive structure called an acervulus in the infected area.
Control methods using fungicides are occasionally used in shade trees and woody ornamentals, but are seldom needed for most trees.
Go to PP 318 Foliage Diseases of Hardwoods
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This profile was written by Becky Bernard
It was last updated on May 5, 2000

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Leafy Mistletoe on Deciduous Trees

(Various locations on campus, quite evident along Hillsborough St.)

Mistletoe on oaks located along Hillsborough St. in front of D.H. Hill Library	Leafy mistletoe, Phoradendron flavescens, is an evergreen parasite of many species of deciduous trees in southeastern and southern U.S. It is best seen in the winter after the leaves have fallen from the host plant.  Many species of Phoradendron are found across the United States, but they are most abundant in the dry areas of the Southwest. The primary hosts are hardwoods, but mistletoe does also occur on some conifers. Phoradendron species have many effects on the host plant, but they seldom cause severe damage. The infected portion of the tree may be swollen, and portions of the tree beyond that point may eventually become deformed and die.  Pruning and the use of various herbicides are effective methods of control.
Phoradendron flavescens growing on red maple.
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	This profile was written by Becky Bernard
	It was last updated on May 5, 2000

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Sooty Mold on Pines

(Located at the east entrance to Kilgore Hall)

Sooty mold is caused by the fungus Capnodium pini. It grows on the exudates of insects, most commonly aphids. The mycelium and reproductive structures produced by the fungus are black, giving the needles a "sooty" appearance.  This fungus does little damage, deriving no nutrients from its host. Most importantly, sooty mold indicates the presence of insects, and may be a warning of a severe aphid problem. Affected trees can often be spotted some distance away because of the blackened foliage.      Sooty mold on pine needles
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	This profile was written by Becky Bernard
	It was last updated on May 5, 2000

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Powdery Mildew

· Located on dogwoods in front of Williams Hall, on crape myrtles behind Williams Hall, and on various other plants around campus

· Best Viewing Time: late April - frost

Powdery Mildew is found worldwide on over 1,000 species of plants. Although the fungi that cause powdery mildew are of little importance to forest trees, they are common on most broad-leaved trees and shrubs. They are economically serious on cereals, and on ornamental plants and flowers.  Powdery mildew is caused by fungi whose hyphae and spores are produced on the surface of leaves giving leaves a white, or powdery appearance. Infection occurs in the Spring, when the ascospores are released from the cleistothecia that formed on the surface of the leaf in the Fall. A high relative humidity and a high temperature favor infection. These conditions often occur in greenhouses and in the understory in forests, where the light intensity is low and there is minimal air circulation.  Although powdery mildews are unlikely to need control efforts on forest trees, they can be controlled after they appear, contrary to some diseases which require preventive sprays.

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Go to North Carolina Powdery Mildew Page
Go to PP318 Powdery Mildew Disease Profile
	This profile was written by Becky Bernard
	It was last updated on June 21, 2000

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Dutch Elm Disease

· Located: Hillsborough Street and Brooks Ave. parking lot and Sullivan Drive across from Central Stores and Administrative Services

· Best Viewing Time: June - August

(Note:  Both of the trees pictured below were removed in July 2000.)

Dutch elm disease, caused by Ophiostoma ulmi (synonym: Ceratocystis ulmi), is one of the most important diseases of shade trees worldwide. The number of trees killed in some areas by this disease is as high as 90%. It was first found in the Netherlands in 1919, and by 1935 was found in almost all European countries. The pathogen was introd350uced into the United States from Europe in 1928 in logs which contained both the fungus and European elm bark beetles. Elm bark beetles are the primary insect vectors.   Leaf symptoms of Dutch elm disease are first evident in June and most prominent in July and August. The leaves turn yellow, curl, dry out, and eventually fall. Usually flagging occurs, in which an entire branch or section of the tree wilts, as see in the picture above. Vascular browning of the outer sapwood in the trunk and stems is also a symptom.  Ophiostoma ulmi enters the tree through wounds made by bark beetles or moves from infected to healthy trees through grafted roots. Only relatively few spores need to be introduced to the tree for infection to occur. The tree reacts to the fungus by producing gums and tyloses, which in turn plug the vascular system of the tree. This leads to wilting and other foliar symptoms. There are many different aspects of control for Dutch elm disease, all of which must be followed to assure success. Elms should be alternated with nonsusceptible tree species, in order to prevent root grafts. Root grafts between diseased and healthy trees may be disrupted chemically or mechanically. Sanitation or eradication of dead and dying elm wood is also a necessity. Elms can also be treated with a systemic fungicide, but this treatment is only effective if the chemical is applied before more than 5% of the foliage is showing symptoms, and it must be continued throughout the life of the tree. Other control measures include the use of resistant elms and the use of insecticides to prevent bark beetle attacks. Go to PP 318 Dutch Elm Disease Profile Return to the top of the page This profile was written by Becky Bernard It was last updated on August 10, 2000