Japanese maples are durable and very easy to grow. Very rarely is it that you see a disease problem on a Japanese maple that is grown in the right place and planted the right way, in the right soil.
If you have recently planted a Japanese maple and the leaves begin to brown slowly from the tips toward the base of the leaf, most likely there is too much water around the roots. Either you are overwatering, or the tree was planted too deep. This can also happen to established Japanese maples if and when the surrounding grade has been changed in a way that forces more water to settle around the root system. Browning of leaves can also indicate "leaf scorch".
In hotter regions of the South, "leaf scorch" can be a problem with Japanese maples during long, hot dry spells.
Leaf scorch is a noninfectious disease or disorder. Scorch most often occurs following prolonged periods of dry, windy weather or bright sunshine when the roots are unable to supply water to the foliage as rapidly as it is lost by transpiration from the leaves. Unfavorable locations, such as sandy or gravelly soil, near obstructions or pavement that restrict root growth, or exposed windy slopes usually promote scorch. Anything that affects the plants ability to take up water, including insect and disease problems, can result in leaf scorch. Herbicides and pesticides may also contribute to scorch. Do not spray on windy days to eliminate drift problems and do not allow mist to settle onto trees.
In mild cases of leaf scorch, the leaves remain attached, and little damage results. In more severe cases, plants may drop many of their leaves prematurely, although such plants do not die. Where leaf scorch occurs each year, such annual stress will gradually weaken the plant, making it more susceptible to insects and diseases.
Look for damage to trees and shrubs on the upper portion on the sunny, southern side and on the windy side. Premature dropping of leaves and twig dieback may occur during the late summer. Symptoms usually appear after drying winds in conjunction with periods of hot, dry weather.
During periods of hot and dry weather, be sure to provide your trees with sufficient water to avoid leaf scorch. Also, if you intend on planting a Japanese maple in full, all day sun, its a good idea to check with your local nurseryman as to which varieties are known to be more heat and sun tolerant!
In the rare event that your Japanese maple contracts a fungus or foliar disease that is not an effect of improper planting or oversaturated soil, we recommend consulting with your local nurseryman, arborist or county extension agent before any treatment begins.
Japanese maples are too valuable a tree to take chances with - particularly older more established trees that are the focal point of the entire landscape, not to mention worth thousands of dollars in cash or property value.
Disease PREVENTION Tips for Japanese Maples
- Water plants at the base to avoid splashing water on leaves.
- Water or irrigate plants in the morning hours to allow any water that might splash on foliage dry during the day. Water left standing on foliage overnight can cause development of fungus and disease.
- Plant Japanese maples in well-drained soils to avoid root rot, leaf spot and other plant diseases caused by wet feet.
- Make sure you select a variety of Japanese maple that will acclimate and thrive in your climate - especially if you garden in a hot and humid climate.