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You are here: Experts > Homework Help > Trees > Trees > LEYLAND CYPRESS
Trees - LEYLAND CYPRESS
Expert: Jim Hyland - 8/7/2008
Question
MY TREES ARE TEN YEARS OLD . PROBABLY PLANTED TOO CLOSE AND MY PROBLEM IS THEY ARE SHEDDING THEIR GREEN. I TOOK OUT 15 BAGS OF FALLEN NEEDLES. CAN I SAVE THEM THE BARK HAS SPLIT AND A LOT OF BLEEDING I HAVE SPRAYED SEVERAL TIMES NOW BUT NOTHING SEEMS TO HELP WHAT NOW
Answer
Although relatively free of serious disease problems, several diseases are becoming more common. These include Seiridium and Botryosphaeria cankers.
One of the most noticeable symptoms of Seiridium canker is yellowing or browning of the foliage on one or more top or lateral branches. The discoloration is most likely to appear in early spring; however, it can be seen at any time of the year. The disease expansion often continues until a significant portion of the tree is destroyed. Upon closer examination, formation of numerous thin, elongated cankers is observed on stems, branches and branch axils. These cankers cause twig and branch dieback. Most of the cankers are slightly sunken, with raised margins, and they may be discolored dark brown to purple. 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.
Another damaging disease on Leyland cypress in 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. dothidea infection in landscape plantings.
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. Sometimes, the main trunk shows cankers that might extend for a foot or more in length. These cankers rarely girdle the trunk, but they will kill branches that may be encompassed by the canker as it grows.
Canker surfaces may be cracked and have a darker color than the surrounding healthy bark. The discoloration often extends several inches below the canker periphery. Little or no resin "oozing" is produced on the infected areas.
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. I do not think they have much chance to survive.
You could try-To minimize water loss and water competition, mulch an area several feet beyond the lowest limbs. Removal of diseased twigs and branches helps prevent disease spread. Remove and destroy pruned material and disinfect pruning tools. Remove extensively damaged trees. During hot, dry summer days, irrigate trees thoroughly around the base of the tree every 7-14 days, depending on soil composition.
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