The pecan tree (Carya illinoinensis ) is the state tree of Texas and is widely grown. There are numerous pecan tree varieties and each variety of pecan tree is adapted to certain areas of the state. The best way to avoid major insect and disease problems with pecan trees is to plant a variety adapted to your area. For information on what fungicides and pesticides to use on your pecan trees, contact your local Agricultural Cooperative Extension Office. Every part of Texas will have a different spraying schedule specific to that growing area, and the approved chemicals for pecan tree diseases changes often.
Cotton Root Rot
Cotton root rot is fatal to pecan trees. It most often attacks trees that grow in poorly drained sites with alkaline soil. It is also known as Phymatotrichum Root Rot. The most obvious symptom of cotton root rot is yellowing of leaves followed by wilting three to five weeks later. In warm weather a cottony mass of fungus can be seen at the base of the tree where the trunk contacts the soil. Occasionally, a pecan tree does not completely die from the disease but becomes so weakened at the base it falls over in high winds. Treatment is with an approved fungicide, but is not always successful.
Pecan Bunch Disease
Pecan bunch disease appears as numerous leafy shoots that grow rapidly in the spring along the limbs of the tree rather than at the ends. This results in thick abnormal growth along a few or all of the tree's main limbs. The disease is believed to be spread by insects, such as leafhoppers, and there is no known cure. It is suggested that affected trees be removed.
Pecan Scab Disease
Pecan scab disease spends the winter in the bark and limb structures of the pecan tree. During the spring, the fungus spreads to other parts of the tree including the nut coverings, or shucks. It appears as an olive or darkened spot on leaves and shucks that becomes black as the season progresses. In severe infections, the entire nut casings containing the nuts become black and fall off prematurely. Also, the leaves fall off the tree before the end of the season. The black spots that are characteristic of the disease can be clearly seen on the freshly fallen leaves and shucks. The best way to avoid Pecan Scab Disease is to plant varieties of pecan trees resistant to the disease.