Why Does My Walnut Tree Look Unhealthy?

Are there brown to black lesions on leaves, petioles, shoots, and/or husks which fade toward the center and may be surrounded by a chlorotic halo?

Are the leaves small, discolored, and drop early, clusters of honey-colored mushrooms may sprout at the base of the plant?

Are the leaves covered with white powder?

Is there a gradual reduction in tree vigor, leaves are yellow and drooping, defoliation occurs prematurely and is followed by dieback of terminal shoots?

Are there galls of various sizes on roots and root crown below the soil line?

Are there small, water-soaked spots on immature fruit that darken and rapidly enlarge bacterial exudate may be present during wet weather?

These symptoms indicate a fungal disease - Anthracnose. Avoid stressing trees by providing them with adequate irrigation and fertilization. Prune out dead or dying limbs from tree canopy to reduce levels of disease inoculum. Control insect pests to prevent stress to trees.

Armillaria root rot is a fungal disease that cannot be effectively controlled once it has become established in an orchard. Diseased or dead plants should be uprooted and removed. Planting resistant rootstocks is the most effective method of preventing the disease.

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Avoid wetting the foliage when watering. Any affected leaves should be cut off and removed. A fungicidal spray may be necessary to protect your plant from further infections.

Blackline disease is caused by a virus that may be introduced from infected graft wood or infected pollen. Use virus-free graft and budwood from English walnut. In areas where the disease is uncommon, immediately remove all infected trees to prevent the spread of the disease.

Crown gall causes brown or white nodules to form around the roots of the tree. As the disease progresses, the roots rot and the tree slowly loses vigor and dies. Unfortunately, there is no treatment for the disease. Buy disease-free trees from a reputable nursery and plant them in loose, well-draining soil. Do not plant walnuts where crown gall has been a problem previously.

Walnut blight is caused by bacterium Xanthomonas campestris. Bacteria overwinter in dormant buds. With bud break in the following year, bacteria infect surrounding leaves and young fruit. The primary method of controlling walnut blight is the application of copper-containing bactericides such as Bordeaux mixture. Bactericides should be applied weekly to protect new growth during periods of wet weather.

If the tree growth is slow with reduced vigor, leaves are turning yellow and wilting, and shoots and branches are dying back, your walnut might have suffered from Phytophthora root and crown rot. Minimize soil wetness and saturation by planting trees in well-draining soils. Drainage can be improved by leveling soil or installing drainage systems. Avoid wetting tree trunks when irrigating.