Why Haven't My Pecans Developed Well?

Do the nuts of your pecans contain insect larvae?

Are there any snouted adult beetles that resemble plum curculios?

Are there any small cream-colored worms and gray moths?

Do the leaves have olive-brown spots on their undersides, shucks are with small, velvety, olive-brown spots?

Does the tree decline, leaves are yellow, dying, but remain on the tree?

Are the leaves covered with a white powdery coating?

Do the leaves have large black or yellowish spots on them?

Do the roots have brown or white nodules formed around them?

Are the leaves at the top of the tree yellow?

The insect pests are called Pecan weevils. They lay eggs within newly formed nut kernels. Larvae that hatch from these eggs feed on the nut and emerge several weeks later through tiny holes in the shell and husk. To control this pest, place dropcloths beneath the tree and jar the limbs with padded poles. Collect and destroy fallen adults. Do this every 2 weeks beginning in midsummer until weevils no longer drop.

Cream-colored worms are called Hickory shuckworms. They eat the kernels of immature nuts that drop early as a result of the infestation. These pests are the larvae of gray moths and the final larval generation overwinters on the ground in dropped shucks. To control shuckworms, pick up and destroy dropped hulls or bury them at the end of the season.

Pecan nut casebearers are green larvae of a gray moth. They spin webs around nuts and then enter to feed. Infested nuts may drop prematurely. Overwintering larvae leave cocoons in early spring and bore into growing shoots, causing wilting. To help control casebearers, pick up and destroy all dropped infested nuts. The parasitic wasp Trichogramma minutiim attacks and parasitizes casebearer eggs.

Pecan scab is a disease that causes these symptoms. Leaf spots may enlarge to large black areas. The spots on the shucks may spread into large, sunken, black lesions. Nuts may drop prematurely. This fungal disease is worst in humid areas and overwinters on infected twigs, shucks and leaves. To reduce infection the following season, clean up plant debris in autumn and knock off old leaf stems and shucks before trees leaf out in the spring.

Cotton root rot is a fungal disease that infects pecans. Roots of infected trees are brownish, rotted and soft. Cotton root rot fungus lives in the soil for 5 years or more, thriving especially in areas with heavy, moist, alkaline soil. An acid-type fertilizer might help mildly affected trees, but dig up dying trees and do not replant with pecans.

The cause for these symptoms is the fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Thin your plants to ensure good airflow. Water plants from bellow to keep foliage dry. Any affected leaves should be cut off and removed. Any commercial fungicidal spray will protect your plant from further infections.

Large black or yellowish spots on the leaves are the main symptoms of blotch. This disease is rarely serious, but in some cases, it can defoliate the trees in late summer. It appears mostly on drought-stressed trees or trees with zinc deficiency. Water pecans regularly. Rake up and discard leaves in the fall to prevent the disease from overwintering.

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 pecan trees where crown gall has been a problem previously.

Rosette is a condition caused by a zinc deficiency. In infected trees, you’ll first notice yellowing leaves in the tops of the trees. Later, leaves become small and entire branches may die back or become defoliated. To treat this condition, spray the leaves with a solution of 1 tablespoon zinc sulfate per gallon of water. You can also add zinc to the soil for a longer-lasting solution.

Wood or heart rot are fungal diseases that may cause problems in pecans. These fungal diseases enter pecan trees that have been injured by a storm or improper pruning. Once the fungus enters the tree, it slowly rots the wood, weakening and eventually killing the tree. To prevent wood or heart rot, prune the tree regularly to remove branches damaged by ice or wind.