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An Orlando Tree Doctor Discusses Tree Diseases

By Advance Tree Pros

Tree Disease Advice from an Orlando Tree Doctor


Anthracnose is a fungal tree disease that infects ash, oak, maple, and sycamore trees growing in Minnesota. The fungus causes dead blotches on the leaves that disrupts photosynthesis and transpiration which can eventually lead to spring leaf drop. As leaves mature they become less susceptible to the pathogen. Repeat defoliation by anthracnose can reduce tree health.

Apple Scab

Apple Scab is a fungal disease that infects apple trees causing lesions on the leaves and fruit. These lesions can also infect stems, resulting in dieback. Most apple cultivars are susceptible to scab and will require fungicidal sprays to prevent the disease. The disease rarely kills its host but causes unsightly defoliation. The pathogen overwinters primarily in infected leaves on the ground.

Armillaria Root Rot

Armillaria is a root rot fungus also called stringy butt rot or white root rot. As its name suggests, the fungus creates mycelial threads that appear on infected tissue like strings. These structures are called rhizomorphs and can grow, under the soil, to distances of up to ten feet. Armillaria may live for decades on its host plant and can infect healthy trees through root contact. Vigorously growing trees are less susceptible to infection. This is a pathogenic organism causing mortality, wood decay, and growth reduction.


Cankers are dead areas of bark that are located on the trunk, branches, or twigs of a tree. Cankers are caused by numerous species of fungi that infect stressed or wounded trees, killing the living bark. Characterized by discoloration, oozing sap, and sunken areas, cankers are some of the most difficult disease problems to manage.

Cedar-Hawthorn Rust

Cedar-Hawthorn Rust as its name indicates is a disease of two urban landscape trees. The disease has two life stages, one which occurs as rust spots on foliage and fruit of hawthorn and one that creates galls on juniper. The disease can be quite devastating to the appearance and health of hawthorn and treatment on this host is necessary to prevent infection. On juniper, the galls may be unsightly when the orange spores are oozing out, but otherwise, they can be easily removed from the infected trees.

Cytospora Canker

Cytospora cankers will infect many tree species, however, the most common Cytospora in Minnesota primarily infects Colorado Blue Spruce. In its native habitat, the disease is not an issue, but in locations where high humidity occurs, it is a very destructive disease that can kill mature Colorado spruce. Most trees are infected and begin to show symptoms after they are established (>15 years). The most effective management is to reduce environmental conditions that stress the tree and to reduce the moisture conditions that increase the spread of the disease.

Diplodia Shoot Blight and Canker

Diplodia is a fungus that will survive in new candles of conifers and will eventually infect the main stem of the tree. While it is in the candles, at the “blight stage” it can be controlled through the continuous use of fungicides over a period of several years. When the disease is in the “canker stage” on the main stem of the tree, the only management that can be done is to increase the vigor of the tree and enhance its ability to callus over the infected tissues.

Dutch Elm Disease

Most infected elms cannot be saved. In rare cases, if the fungus has not moved into the root system, physically cutting out the infected portions of the tree, with a process called tracing, can save the elm.

Oak Wilt

Oak wilt is a lethal disease caused by the fungus Ceratocystis fagacearum. The fungus invades and disables the water-conducting system in white, red, and other oak species. Different species of oaks vary in susceptibility to the disease. Red oaks typically die within 4 to 6 weeks of initial symptom development, while white oaks may survive or take 1 to 6 months to defoliate and die. Oak wilt is most often spread via root grafts between interconnected and grafted root systems. Root graft disruption and fungicidal treatments aid in preventing the spread of oak wilt.

Rhizosphaera Needle Cast

Rhizosphaera needle cast is a foliage disease of spruce trees. It causes significant damage to trees growing outside of their native range. Older, inner needles show symptoms first. As the disease progresses, newer needles will exhibit symptoms. Infected needles first appear mottled or speckled with dull yellowish blotches. Later, the needles turn brown to purplish-brown. The needles are dropped (cast) anywhere from 3 –15 months after infection depending on the variety of spruce infected. Branches begin dying if they are defoliated in 3-4 consecutive years. Larger trees are rarely killed, however, they may become so disfigured that they lose all of their ornamental value.

Spruce Needle Drop

Spruce Needle Drop (SNEED) is a branch disease of Colorado, Black Hills, and Norway Spruce that is only a problem on stressed trees. The pathogen was first described in France and in the past 10 years has been found on urban trees throughout the Midwestern United States. The disease is not found on or in the needles but instead is found on the woody tissues at the base of the needles. It is not a problem on healthy trees in good growing environments. It will result in needle drop and branch death on trees that are unhealthy or are under a stress such as a drought, root constriction, or are planted in poor soils.

If your tree looks as if it’s having some health issues, give us a call. We are Orlando’s certified arborists and chances are, we can help you save your tree through proper tree trimming and other approaches.