Pecan trees are North American natives that thrive in USDA Zones 6 through 9. These deciduous shade trees have vigorous growth rates and can reach mature heights up to 150 feet, with a spread at least half its height. These massive trees can quickly become the homes for birds, animals and pests. In this, the tree is susceptible to several diseases that can be injurious to these trees, if left untreated.
Pecan scab is a disease that can cause detrimental effects to the pecan tree. This disease travels by fungal spores that infect the newly developing foliage and nuts. The infected leaves develop small, dark-colored spots and lesions. The nuts become stunted and are often covered in fungal scabs. The Mississippi State University Extension explains that the severely infected pecan tree will experience premature foliage and nut defoliation while developing a blackened appearance. Although young foliage and nut tissue are susceptible to this disease, these areas develop resistance as it matures. Preventing this disease is best completed by selecting resistant pecan varieties. The disease can be controlled with multiple and well-timed fungicidal spray treatments that cover the tree's entirety. Professional applications are recommended for accurate treatment.
Powdery mildew is a common fungal disease that infects the newly developing foliage and nut tissue of the pecan tree. The infected areas develop small, white spots that accumulate until the surface develops a covering of powdery, white mildew. This fungal covering inhibits the penetration of sunlight and air to the surface of these tissues, which results in the growth stunt and dieback of the foliage. Mature foliage is generally resistant to powdery mildew. The actual pecan nuts are usually unaffected by powdery mildew since the disease does not penetrate the shuck. The mildew is easily washed away by rain or water hose. Powdery mildew can be controlled with regular fungicidal spray treatments that cover the entire tree.
Crown gall is a soil-borne bacterial disease. This disease infects the pecan tree through fresh wounds that are caused, not only by pruning cuts, but by weather damage, animals and insects. Crown gall primarily infects the lower areas of the tree, including the roots, trunk and lower branches and stems. Still, the University of Kentucky Cooperative Extension explains that all woody areas of the tree can be infected. Afflicted trees will develop rough, woody galls near the point of infection. Infected pecans will also experience growth stunt and dieback. To control the disease, the woody galls must be pruned from the area with sterile pruning shears that are sterilized between each cut. Chemical treatments are also effective in reducing the spread of disease when combined with a pruning regimen. Severely infected trees will become girdled with galls and die from the disease. These trees should be removed and destroyed.