Pecan trees are a staple in many lawns across Louisiana. Homeowners love their shaggy bark, long, flowy leaves, and of course, pecans! There have been calls this spring about pecan trees failing to produce. Unfortunately, there is no easy answer. Pecan trees require yearly fertilizer applications and sometimes need lime. Weather conditions play a role in nut production too. During a wet year trees may not produce as well due to pollination issues or disease. Nevertheless, there are a few things you can do to try and bring your pecan trees into production.
Start with a soil test. Testing your soil can determine if your soil is too acidic or alkaline. Soil in our area is normally acidic and pecan trees could benefit from an application of lime. Pecan trees also need adequate zinc in the soil to produce a crop. A soil test will help you determine the specific requirements for your trees.
Pecan trees require yearly fertilizer applications. Fertilize in late February to early March. Broadcast fertilizer around the root zone and extending about 2 feet past where the tree limbs stop. Use 2 lbs. of 13-13-13 per inch of trunk diameter (measured at 4 feet above the soil level) up to 20 lbs. per tree. Example: a tree with a 10+ inch diameter should receive 20 lbs. of 13-13-13. It may take up to two years of proper fertilization before the tree begins to produce.
A major disease affecting pecans is a fungal infection we know as scab. Scab causes black spots to form on the tree leaves. The spots usually start on the underside of the leaf and eventually move to the shuck causing black, sunken spots to appear on the outside of the shuck. Pecans affected by scab will have either empty shells or half formed nuts. Unfortunately, there is not much a homeowner can do to treat or prevent scab. A regular fungicide schedule will prevent it, but it is neither practical nor economical for homeowners to spray mature trees. Orchard owners have special high pressure spray equipment for spraying trees. The best defense a homeowner has against scab is to plant scab resistant varieties and practice good cultural controls. The fungus overwinters in fallen tree leaves and is made worse by wet, cool weather. Collect and discard all fallen leaves to help manage the severity of infections. Fungi love moist environments. You may also prune your trees so that airflow reaches the branches and dries them out more quickly.
Pollination affects pecan production and quality. Pecans trees must have a cross pollinator within ¼ mile radius of the tree. If you are planting pecans in your yard you will need to plant two varieties with opposite blooming characteristics for pollination to occur. Type I varieties shed pollen early and Type II varieties shed pollen late. Type I varieties have less scab resistance than Type II but some recommended varieties are: Caddo, Oconee, and Jackson. Type II varieties with excellent scab resistance are Candy, Elliot, and Sumner. Choose one from each type for new plantings and remember that it may take six to eight years for your pecan trees to begin production.
A few folks have called me complaining about worms in their pecans. It is important to properly identify the insect before deciding which treatment method to pursue. Here are some insects commonly plaguing pecan trees:
Pecan weevil- adults have a long snout and the larva feeds on the nut. The females overwinter in the soil beneath the tree and emerge from August through October. They crawl or fly up the tree and lay their eggs in the nuts. Larva feed on the nuts then chew an exit hole out of the shell. Pecan weevils can be managed by spraying the soil beneath the tree and up the trunk as far as you can reach with a product containing carbaryl, such as Sevin. Spray in mid-August and consider applying a second application 14 days later.
Aphids- aphids are not usually a problem with pecans but if you notice the tiny green or black insects, along with the honeydew they excrete, treat the soil with a soil drench containing imidacloprid. A product such as Ferti-lome Tree and Insect Soil Drench can be found at your local garden center. Treat about 6 weeks after pollination if needed.
Pecan nut casebearer- is a small light gray moth about ¼ inch in length. Larva feed on leaves at bud break and immature nuts. Casebearers can be controlled with Malathion or Spinosad in early May
Pecan phylloxera- creates green galls on the leaves and galls on twigs. Spray Malathion at bud break in the spring when leaves are about .75 – 1 inch long.
It seems like a lot but if you continually monitor your trees for insects and disease, hopefully you will catch these pests early and have a nice crop of pecans in the fall. Happy picking!