Cracked bark in infected areas is often accompanied by extensive resin exudates that flow down the diseased branches. The cambial tissue beneath oozing sites is discolored with a reddish to brown color. In the landscape, the causal agent, Seiridium unicorne , over-seasons in cankers on diseased trees. Environmental stress, predominantly drought stress, favors infection and canker development. Seiridium cankers enlarge up to three times faster on drought stressed trees than on adequately irrigated trees.
Spring freeze and ice injury often predisposes trees to infection. Fruiting bodies of the pathogen, called acervuli, appear on the canker as small black dots that are barely visible to the naked eye.
Fungal spores are spread to other parts of an infected tree or to other trees by splashing water either from rain or irrigation. The fungus also can be spread on pruning tools. Long distance spread occurs through the transport of infected cuttings or plants, or possibly by insects.
New infections occur when spores lodge in bark cracks and wounds. Infection through lenticels may occur following hot, dry weather. Proper establishment and care are the best defenses against Seiridium canker in residential and commercial landscapes. Due to its relatively shallow root system, plant Leyland cypress in tilled and amended soils to encourage plant vigor. Avoiding excessive watering and heat stress is vital to establishment of a healthy Leyland cypress.
To minimize water loss and water competition with other plant species such as turf, mulch an area several feet beyond the lowest limbs. During hot, dry summer days, irrigate trees thoroughly around the base of the tree every days, depending on soil composition. Take special care for trees located near drive-ways, paved areas or heat-reflecting buildings.
Providing adequate irrigation during periods of drought is the best defense against Seiridium canker disease. Sanitation, such as removal of cankered twigs and branches, helps prevent disease spread. Destroy pruned materials, and disinfect pruning tools by rinsing in rubbing alcohol or a solution of 1 part bleach to 9 parts water. Remove extensively damaged trees or trees that are damaged in the main trunk. No cultivars or selections are known to be resistant to the disease. In the landscape, fungicides are seldom used and they provide no control once an infection has taken place.
Another damaging disease on Leyland cypress in Georgia landscapes is a canker and dieback named Botryosphaeria Bot canker, caused by the fungus Botryosphaeria dothidea. This aggressive disease affects a number of woody shrubs and trees worldwide, and it has been reported on azaleas, rhododendrons, flowering dogwoods and redbuds, among others.
Plants suffering from environmental stresses freezing, drought, or heat or wounds are particularly susceptible to B. In the landscape, Bot canker symptoms resemble those caused by Seiridium canker. Bright, rust-colored branches and yellowing or browning of shoots or branches are the first observed symptoms.
Closer inspection reveals the presence of sunken, girdling cankers at the base of the dead shoot or branch. Armillaria is very easily distinguished by the white mycelial growth just below the bark at or just below the soil line. Leylands are very susceptible to a host of diseases. The most prevalent that I have run into between Beaufort, Hyde, Tyrrell and Washington counties is Passalora needle blight. This disease begins to appear on the lower branches near the trunk and spreads towards the tips, working its way up the tree until the entire tree is devoid of foliage.
Seridium canker is another disease that is often diagnosed on Leylands. This disease causes a sporadic tip dieback all over the tree. Upon further investigation, cankers, or open scabs oozing sap, can be found on those branches. Lastly, there are insect pests that affect these trees, the most notable of which is the bagworm. These tiny caterpillars larvae of moths hatch from within the bags in May.
The caterpillars begin to feed and construct their bag from plant parts. Affected needles may or may not fall early and trees suffer from tip dieback. Cercospora needle blight begins at the base of the plant and works up.
This fungal disease first appears as brown, discolored needles that then change to gray. Needle tips do not change color but infected foliage drops early. To control these diseases, remove and destroy affected plant parts to decrease the severity of disease. You can also spray tree blights with copper-based fungicides. Although Leyland cypress shrubs are affected by a variety of root rot problems, the rot disease that may lead to browning is annosus root rot. This fungal disease most often affects landscape trees by invading newly cut stumps that are near your Leyland cypress trees.
As the fungal pathogens work their way into the roots of the stump, any nearby trees with roots that make underground contact with the infected stump may, in turn, become infected. Winter cold injury can lead to greater infections from fungal diseases, such as Seiridium canker. Winter cold injury can often lead to greater infections from a few common fungal diseases that affect foliage, stems, and branches such as Seiridium and Botryosphaeri a cankers , as well as Cercospora needle blight.
Symptoms of canker diseases include branches that start to turn yellow to reddish-brown.
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