The Leaves of My Otto Luyken Laurel Are Turning Brown

Bacterial Leaf Scorch

• Leaf scorch is the descriptive term for the damage Xylella fastidiosa bacteria does to laurels like Otto Luyken. Transmitted by insects that feed on the water- and nutrient-conducting tissues, bacterial leaf scorch turns leaves dry and brown. The infection is similar to drought damage. As the infection worsens, entire leaves may turn brown and the plant can become stunted or develop deformed growth called witch's brooms. An antibiotic injection may help control the symptoms, but there is no cure and no practical way to repel insects that carry the disease. Have a sample of infected plant material tested to determine whether the leaf scorch is bacterial or physiological.

Cultural Problems

• Leaf scorch caused by cultural problems closely resembles bacterial leaf scorch. The damage occurs most often during the summer and is usually caused by poor soils, too much fertilizer, excessive heat or too little water. The leaves brown along the margins first, with the discoloration advancing inward between the leaves' veins. Browning may be more severe on the outer section of leaves, especially on the part of the plant that receives the most sunlight. In most cases, improper watering is the culprit. Water the soil to at least 12 inches deep. Infrequent, slow, deep watering gives the plant more usable moisture than frequent, shallow watering. Let the water trickle from the garden hose or use a soaker hose so the root system can absorb moisture properly.

Fungal Infections

• If the Otto Luyken's leaves are turning brown in only one area of the plant, it could be suffering from Botryosphaeria, a fungal infection that causes wilting and dieback of one or more branches. Cut into the wood of the infected branch; if the wood is brown and discolored rather than white, the plant is infected. Botryosphaeria fungus can cause cankers, or lesions, on larger branches. No fungicides are available to treat the disease. Other fungi, including Cercospora, Blumeriella and Wilsonomyces carpophilum cause leaf spots and shotholes. Have the infection diagnosed and apply a fungicide formulated to treat or prevent the specific fungus.

Prevention

• Keep the Otto Luyken as healthy as possible to help it withstand and recover from diseases. Re-evaluate cultural practices such as fertilizing and watering to make sure the plant is not getting too little or too much of either. Take a soil test to determine which, if any, nutrients the soil lacks and apply fertilizer that provides those nutrients. Prune out dead and infected areas of the plant and disinfect pruning tools in between cuts to avoid spreading disease. Remove weeds and plant debris to eliminate hiding places for pathogens and insects. Apply fertilizers and fungicides according to label directions.