By Willie O. Chance III
University of
Georgia
Certain diseases are becoming more common to Leyland cypresses. Two are especially widespread.
Bot canker kills individual branches in the tree. The foliage may turn grey-green before it dies. The dead branch will have darker bark and a sunken canker where the dead part of the branch begins.
Limbs on trees infected with Seiridium canker turn yellowish and then brown to grey when they die. The cankers on the main stem are sunken and reddish and ooze sap. Many cankers can be on a single limb.
No spray will control these diseases. Entering wounds in the tree, the diseases are worse during stressful weather. The main control is to keep the plant in good health so it can resist the diseases.
Dry weather is a big factor in the spread of these diseases, so be sure to water Leyland cypresses during a time of drought. If plants get dry, they're more likely to get sick.
Don't water more often than twice a week during drought. Once a week is better. Wet the soil down to 12 to 18 inches when you water. Soil must dry out between watering or the roots may die.
Apply three-quarters to 1 inch of water once a week if you use sprinklers. Soaker hoses are better because they keep the foliage dry, which may reduce disease problems. Run soaker hoses once a week just long enough to wet the soil 12 to 18 inches deep.
Plant Leyland cypresses in well-drained soils in sunny places. Mulch them after you plant, but use only 2 to 4 inches of mulch. Don't use landscape fabric unless the soil is very well drained.
Don't plant Leyland cypresses in wet soils or poorly drained areas. They may respond to wet feet by getting sick or dying. Check the soil drainage before you plant or if the tree has problems.
To see if your soil drains properly, dig a hole about a foot deep and wide. Fill it with water. If it takes longer than eight hours for the water to drain out, the soil is probably poorly drained.
Don't plant Leyland cypresses less than 8 feet apart. As the plants get big enough for the limbs to touch, remove every other tree. If the limbs rub together, they cause wounds that can be infected by diseases.
If you already have these diseases, first cut out the dead limbs. Be very careful to cut way back into good, live tissue. Cutting diseased limbs and then immediately cutting good limbs may spread the disease.
If you like, while you prune you can periodically clean your shears with rubbing alcohol. Generally, don't cut the main stem on a Leyland cypress. If you have cankers on the main stem, it's best to remove the tree.
Next, find out what needs to change about the way you're growing the plant. The main problem is probably improper watering. Solving tree problems often comes down to watering and root care, since we can do little else for trees.
Since these diseases are getting to be very common, consider this when you plant. Avoid plants like Leyland cypress and Japanese cedar (Cryptomeria) if you can't give them this kind of care.
(Willie Chance is a Houston County Cooperative Extension agent with the University of Georgia College of Agricultural and Environmental Sciences.)
