My Northeast Locust Tree Is Turning Yellow
- Cankers and root collar rot diseases are the most common problems of locust trees. In the Northeast, symptoms of cankers include sunken areas or open sores on the bark, yellow or dropping leaves and reduced growth. Collar rot causes yellow or discolored areas of bark at the soil level and premature fall coloration. To treat cankers, prune out dead and diseased branches to prevent infection. Remove the branch at least 12 inches below the canker and disinfect pruning tools in a chlorine bleach solution. Cut out cankers in the trunk or large branches, cutting 1 inch into healthy wood. Mulch the area beneath the tree to avoid lawn mower or string trimmer injuries. To treat root collar rot, allow the soil to dry out between waterings. Remove plastic landscaping fabrics and mulch with wood chips instead. Position sprinklers away from the tree, as excess water contributes to the disease.
- Exposure to triazine herbicides can cause yellowing leaves, especially yellow leaves with green veins that resemble chlorosis due to iron deficiencies. Water the tree immediately to leach the herbicide from the soil. With proper care, the Northeast locust should recover.
- Insects, such as the honeylocust plant bug, spider mites and leaf hoppers, may cause leaves to turn brown or yellow. These insects suck the juices from black locusts and honeylocusts. They generally don't cause significant harm to healthy trees, but may defoliate young or stressed trees. Dislodge them with a heavy stream of water or spray the tree with insecticidal soap or dormant oil in early spring.
- Tree stress is harder to identify and can come from multiple sources. Planting locusts near sidewalks may cause reduced growth and yellowing leaves due to soil compaction. Excavation due to construction may damage roots. Drought or excessive water may also contribute to a locust tree's demise. Keep the tree healthy by placing it in a sunny location with plenty of room to grow. Water it weekly during dry weather in the Northeast.
