Leyland cypress threatened by overplanting
Crowded in housing developments and small building lots make border shrubs like Leyland cypress the perfect shrub for quick privacy. The shrub grows quickly and is somewhat narrow making a perfect green fence or border.
Unfortunately, these shrubs are now over planted, sharing the same fate as red tipped photinias. Red tips are no longer planted because of entomosporuium leaf spot, a foliar disease that rapidly defoliates and eventually kills the shrub.
Leyland cypress is rapidly approaching red tip’s fate.
Overplanting has made the plant very susceptible to insects and untreatable diseases. Bag worms are now a serious problem that first appeared about 5 years ago. Moth larvae hatch in the early summer forming a protective cocoon. Scores of larvae feed during June and July with the potential of defoliating the shrub.
These insects can completely defoliate a shrub in a matter of days, easily killing the plant.
Sprays of Sevin or Thuricide in the early larval stage easily kill the insect. Those with a few larvae can hand pick them off the shrub. As the insect matures, they increase in size and become and resistant to insecticides.
As the summer progresses, the larvae become very difficult to control. After these pupate, they are impossible to kill.
Large shrubs can be difficult, or in some cases impractical, to spray.
Fungal diseases are also becoming a major a problem on Leyland cypress. Root rots, needle blights and canker diseases are taking their toll on the shrubs. There are six known fungal diseases that easily kill Leyland cypress. Phytophthora root rot and Armillaria root rot are two of the root diseases that are killing them in Rowan County. Plants decline slowly and eventually die. Unfortunately, there is no control for these diseases. Removal of affected plants is the best solution.
Cankers are fungi that affect both trunks and limbs causing limbs to dieback. Prune out the infected portions and avoid heavy fertilization. If possible, irrigate during dry periods.
Mulching will help, but avoid excessive applications. Spacing plants no closer than five feet allows for good air movement, reducing the incidence of fungal disease problems.
Those considering planting a hedge or replacing dying Leyland cypress should consider alternatives such as the new arborvitae cultivars or Cryptomeria japonica www.ces.ncsu.edu /depts/hort/consumer/factsheets/trees-new/cryptomeria_japonica .Hollies such as ‘Nellie R. Stevens’ and Greenleaf holly do well as border or screening materials.
Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com, http://rowanmastergardener.com, e-mail Darrell_Blackwelder@ncsu.edu