QuestionQUESTION: Hello Jim. I am having difficulty with my leland cypress trees. We planted these eight trees in the back yard in spring 2008 to grow a privacy screen. We watered the trees a lot to get the root system going. In 2009 they did fine and continued to grow. In 2010, we lost one -- the leaves turned brown and the tree just died. This year, I continued to water the trees, even though we were in the midst of a drought here in North Louisiana. Then around late July, I started noticing more and more of the green leaves turning to brown. I also noticed a sap on the bark of some of the trees. That same sap was on the tree that we lost last year. Now, almost all of the trees' leaves have turned brown, with some green leaves remaining. So my questions are: what happened? Was it the drought or a disease? I've been hearing more and more that leland cypress trees are disease prone, so if this is the case, I won't be buying these anymore. Also, what type of trees do you recommend my purchasing to replace these trees? And, is it worth replacing trees if future summers will be as hot and dry as this one was? Many thanks for your help!
ANSWER: Leyland cypress trees are subject to a couple of canker type diseases that effect the foliage.
Seiridium canker is probably the most important and destructive disease on Leyland cypress in the landscape. Although the fungi Seiridium cardinale, Seiridium unicorne, and Seiridium cupressi have been reported to cause disease on Leyland cypress and other needled evergreens, only Seiridium unicorne is most commonly associated with cankers and twig dieback on Leyland cypress.
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.
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 7-14 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. Do not over water.
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 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.
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. In the landscape, no fungicides are recommended to control Bot canker.
WHAT TO DO
On trees already infected, the best control is to prune the brown #dead# branches from the tree. This will make the tree look better, but also it will reduce disease spread by reducing the fungal innoculum. Once this is done, then irrigation is the best remedy to prevent any smaller cankers from expanding to kill more of the plant.
The one thing that has to be stressed is that the infection occurred years ago, and it is only now after the cankers have enlarged that the symptoms are evident. Therefore, fungicides are not effective in controlling the diseases at this time. There is no way to spray the entire tree at very regular intervals #every 7 days# throughout the year to try to prevent diseases that can be effectively prevented by not injuring or stressing the trees such as don't plant trees too close together and irrigate during periods of drought or in summer when rain cannot be counted on.
Due to its being susceptible to several diseases the life expectancy of Leyland cypress is relatively short #15-20 years # When disease start affecting them they seem to break down and die fairly quickly. Not knowing where you are located it is hard to recommend a replacement but Green Giant arborvitae maybe a good one.
Thuja 慓reen Giant?"arborvitae" - new, hybrid arborvitae; a Leyland cypress replacement; 30?tall, FAST growing , medium-green color; great plant.
Check with the local nursery and see if they carry it and if they think it will grow in your area
---------- FOLLOW-UP ----------
QUESTION: Thanks Jim so much for your helpful information. I wanted to follow up and let you know I live in north Louisiana. We have been experiencing a drought this summer and are still going through the effects this fall, with the city still advising water conservation. Thanks for your recommendation about the green giant tree as a replacement. My question, is: how drought and disease resistant are these green giant trees? If we have another drought next summer, do you think it would be beneficial to replant trees now? Thanks again for your help.
Answer'Green Giant' arborvitae is virtually maintenance free, as well as pest and disease-resistant, making it a superior alternative to the disease-prone Leyland cypress #x Cupressocyparis leylandii#. They prefer full sun but do well in partial sun unlike your regular arborvitae that does not tolerate full hot sun well. They are drought tolerant as well as disease and insect resistant. They do not have problems with bag worms as your regular arborvitae do.
When your Green Giants are young, make sure your tree gets water during extended dry spells, particularly in the summer months. Drooping branches are a sign of both over or under watering, so take great care of your tree. Also these trees love fertilizer Use only a slow-release fertilizer for the first growing season and do not use stronger fertilizers until your tree becomes more established. Your choices should be either water soluble # Miracle Gro or equivalent #, or granular # Holly Tone is excellent #. Other granular types with 6-12-12, or 10-10-10 ratio is acceptable. It is best to fertilize in early spring, and again in mid fall and to avoid feeding during hot summer months, and directly after transplanting.
Water once a week with 1 inch of water--place a pan under the trees and turn the sprinkler on and when the pan has 1 inch of water in it stop. During droughts water every third day unless it rains. A drought would be it has not rained in 2 weeks in the hot summer.
When you plant them dig the hole twice the size of the container or root ball and as deep. Fill with good top soil or potting soil. Mulch around the trees with not more than 3 inches deep of organic mulch not piled up on the trunk. Pine straw is good. This will help hold moisture around the roots.
Yes I would plant them but would wait until after the first of the year Jan -Feb. or March. North La. you should not be concerned with frozen ground.
