One of the more widely used plants in our landscapes is the Leyland Cypress. They are used as specimen plants, hedges, screens, wind barriers and Christmas trees.
The reason so many people like to plant them is that they can grow three to four feet every year while they are young. As they grow older, the growth rate will slow down. The trees can grow to a height of 40 feet and have a spread of 20 feet. They rarely get to be this size in our area.
There are two diseases that attack Leyland Cypress, and there is no cure for them. As I travel around the county, I see Leyland Cypresses showing signs of these diseases: Seiridium canker and Botryosphaeria (Bot) canker. So, what do these diseases look like? At first, individual limbs will start to turn yellow, then brown, and the limb dies. You can see these limbs scattered all over the tree. These cankers enter the limbs when the plant is stressed by drought, freezing temperatures and being planted too close together.
In Georgia, Seiridium canker is the most important and destructive disease on Leyland Cypress. The symptoms normally occur in the spring, but this year we are seeing more now because of the drought. The disease will continue to spread on the tree until a significant portion of the tree is destroyed. When the canker reaches the trunk of the tree, the cankers can girdle the trunk and kill the tree.
If you look at the dead or dying limb, you will find a lesion or canker on the limb. This lesion will have a sunken center with raised margins. The canker can have resin or tree sap oozing from it. If you were to prune out the diseased limb, the cambium tissue around the canker would be reddish to brown in color. The disease is spread by spores that are splashed by water from infected sites on the tree. The spores can be transported long distances by moving of infected cuttings or possibly by insects. The spores lodge in bark cracks and wounds and start the cycle over again.
The second disease is Botryosphaeria canker or Bot canker. The symptoms for this disease are the same as for Seiridium canker. The limbs will turn yellow, then brown. This disease attacks other plants in the landscape, and these plants can be host plants for this disease. The plants include azaleas, flowering dogwoods and redbuds.
Plants that are suffering from stresses such as freezing, drought, heat or wounds are more susceptible to Bot canker. The canker surfaces on the limbs may be cracked and have a darker color than the surrounding healthy bark. The discoloration often extends several inches below the canker borders. With the Seiridium canker, there is sap oozing from the canker, but with Bot canker there will be little or no sap oozing. Bot canker is spread by spores, and the spores are mainly spread by water splashing on infected parts of the tree. The spores of this disease can be spread long distances by the wind.
So, how do you control these diseases? There is no chemical control for either, but there are several cultural practices you can use to produce a healthier plant.
The process of growing a healthy plant starts at planting. The trees need to be planted in well-drained and well-tilled soils. The planting hole needs to be three to four times larger than the root-ball, and the tree needs to be planted at the right depth. Also, when planting Leyland Cypress, you need to space them the right distance apart. Remember, these trees can reach 40 feet in height and 20 feet in diameter. You need to plant them apart 10-15 feet on center. If you plant them closer than that, you will stress the trees.
The trees also are stressed by competition for water. Since drought plays such a large role in Leyland Cypresses getting these diseases, you need to mulch them with three to five inches of mulch. The mulch needs to extend several feet beyond the lowest limbs of the tree. Also, you can remove the infected parts of the plant to help reduce the spread of the disease. When you prune an infected limb, you need to disinfect the pruning tools by using rubbing alcohol or with a solution of one part bleach to nine parts water. You need to disinfect between every cut.
If you have Leyland Cypress, sooner or later you will have either one of these cankers. The key is to keep the trees as stress-free as possible.
Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at email@example.com. The Extension Web address is www.ugaextension.com/columbia.
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