Regular Pecan Bearing

Why don't fruit and nut trees produce every year? This phenomenon is referred to as alternate bearing. One of the main reasons why a poor fruit year follows a year of abundant harvest is improper leaf maintenance.

Early defoliation of pecan trees can be the result of a combination of problems including disease, stress, and/or insects.

Scab and downy spot are the diseases that may cause defoliation. Scab appears as small black lesions that later enlarge and completely blacken the pecan leaf, eventually killing it and causing defoliation. Scab will also attack and kill the shuck or outer covering of the pecan, which results in a poorly filled or hollow pecan. Downy spot causes the leaves to drop in August prohibiting the from filling the nuts.

Water stress and various foliar feeding insects that compound leaf drop problems can also be associated with disease. Such insects as aphids and mites attack pecan leaves, contributing to early defoliation.

The variety of pecan dictates the severity of the disease problem. Many of the older varieties, such as Burkett, Delmas, Success and Mahan, are very susceptible to disease. On the other hand, varieties such as Desirable, Choctaw, Cheyenne and Shawnee are quite disease resistant.

Pecan varieties that are not considered to be disease resistant can only be kept in production through the spray application of pesticides throughout the growing season. However, pecan trees are too large to be sprayed with conventional garden equipment. Most homeowners do not have spray equipment that will reach the top of a 30-foot tree.

Therefore, for homeowners who want to produce pecans in the backyard, the most logical solution is to plant the disease resistant varieties listed above. Those varieties have sufficient inherent disease resistance to make spraying less essential. These varieties may, however, require some insect control throughout the season.

Pecan producers with established trees that are more susceptible to disease may consider "top working" (grafting) trees to a more resistant variety. This should be done in early spring.

Spraying backyard trees is not considered to be very economical. The cost of pesticides and the length of the spray schedule make it very impractical and costly to spray and maintain pecan trees on a commercial basis.

Another factor essential to maintaining productive pecan trees is an annual application of fertilizer. Pecan producers should fertilize in February with one pound of a slow?release lawn fertilizer (such as 19?5?9) per each diameter inch of trunk, measured 3 feet from the ground. Fertilizer should be applied at the drip line of the tree and lightly incorporated if possible. This is in addition to lawn fertilization.

Trees must also have adequate amounts of zinc. Soil applications containing zinc have proven ineffective, so foliar sprays should be used. Two to 3 applications of a zinc product such as zinc sulfate or NZN should be made at 2- to 3-week intervals beginning at bud break. NZN should be used if sprays contact peach or plum trees since defoliation can be caused if zinc sulfate is used.

In late August and early September, aphids and mites may cause premature shredding of leaves. Premature defoliation will certainly affect the quantity and quality of this year's crop, as well as next year's harvest. Aphids and/or mites cause a general yellowing of the leaves. A severe infestation of either or both of these pests can completely defoliate the trees in mid- and late-summer.

With this information, those homeowners who have nonproductive pecan trees can do something about it. Homeowners who want to plant a pecan tree in or around the yard should carefully consider the location of such trees-they get big! Many folks mess up the future beauty of their lawns by planting "cute little trees" in the wrong place. The problem arises when the "cute little tree" grows into such a monster that swings can be hung on limbs growing through the living room! A pecan tree can be a productive asset or a perpetual liability.