Poor variety and Disease and Insect pests —Pecan cultivars (varieties) vary in production capacity, nut quality and susceptibility to disease and other problems. Some varieties will rarely produce a good crop when trees are unsprayed because the trees are extremely susceptible to pecan scab, a fungus disease. Pecan scab seriously limits production on unsprayed pecan varieties. Even varieties previously resistant to scab are being affected. Several other diseases can cause early leaf drop and decreased production. New recommended varieties for homeowners with excellent to good disease resistance are — 'Gafford', 'Excel', 'Lakota', 'Headquarters', 'McMillan', and 'Baby B'. Check www.alabamapecangrowers.com for more information and availability.
Aphids, pecan weevils, hickory shuckworms and several other insects can limit production. Removing and destroying fallen leaves, shucks, nuts or twigs are measures that aid in control of many insects and diseases. Spraying may not be feasible for growers with only a few trees, but if you would like spray recommendations for controlling pests, they are available from your local Extension office.
Poor soil — Pecan trees grow best on sandy loam soils with well-drained subsoil. Growth and production is often poor on heavy clays, poorly drained soils and on deep sands unless an intensive irrigation and fertilization program is maintained.
Inadequate lime or fertilizer — Lack of lime, nitrogen fertilizer and zinc are common limiting factors in pecan production. Fertilize according to soil and leaf sample recommendations. Apply fertilizer in March on large trees. For young trees, fertilize in March with 13-13-13, lime and zinc. Apply half ammonium nitrate in April, half in June. Broadcast fertilizer on the surface in a circle twice the branch spread of the tree.
Too much or too little water — Waterlogged soils where water stands do not provide aeration for roots. Lack of water, especially during dry periods of summer, frequently results in reduced yields and quality, and in weakened trees that may be less productive in following years. Choose well-drained soil, provide drainage for excess water and keep trees watered during dry periods.
Poor pollination — A single isolated pecan tree usually won't be effectively pollinated, since most varieties shed pollen either too early or too late to pollinate the female flowers of the same tree. If a number of seedling pecan trees or trees of several different varieties are already growing within a few hundred yards, a tree for pollination is probably unnecessary. Another reason for poor pollination is wet weather during April and May. Rain washes off pollen and may restrict movement of pollen by wind.
Overcrowding — Pecan trees must have good exposure to sunlight to produce good crops. When limbs begin to overlap limbs of neighboring trees, remove the least desirable trees to prevent overcrowding.
For more information, contact your local county Extension office or visit us online at www.aces.edu.