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Pecan Varieties for Georgia Orchards

Lenny Wells — Extension Horticulturist Pecans
Patrick Conner — Research Horticulturist/Pecan Breeder

Disease Resistance
Alternate Bearing
Precocity
Nut Maturity and Harvest Date
Pollination Type
Nut Size and Quality
Literature Cited
Photos of Varieties

The most fundamental step in pecan production is the selection of varieties or cultivars to be planted in the orchard. Planting the wrong pecan variety can be a costly mistake, resulting in considerable expense. Each variety has its own strengths and weaknesses and, based on the orchard characteristics, may or may not be suitable for a particular situation. Regardless of the care taken in choosing an appropriate variety, experience has taught many growers that any variety may in due time fail to be as well adapted as it at first appeared. Among the most important factors to consider when selecting a variety are disease resistance, alternate bearing, precocity (the bearing age of the tree), harvest date, pollination type, nut size and nut quality.

Disease Resistance

Pecan scab is by far the most serious challenge facing pecan production in Georgia. Our warm, humid climate is ideally suited to the pecan scab fungus, which can devastate susceptible varieties given the right environmental conditions. Some orchards may require up to 15 fungicide applications in a season, and many varieties are too scab susceptible to be recommended, even with fungicide application.

The scab fungus spreads relatively slowly from one region to the next. A particular variety may seem scab resistant in one location and be very susceptible elsewhere. Research has shown that the scab fungus is composed of multiple races, each suited to grow best on a small number of varieties. Therefore, the resistance level of a particular variety will be influenced by what races are present in the orchard in which it is grown.

For example, an orchard composed largely of ‘Desirable’ trees will probably have a large proportion of scab fungus, which is suited to grow on ‘Desirable.’ If a few trees of ‘Sumner’ are planted in this orchard, ‘Sumner’ may not at first be much affected by scab. This is because the majority of spores that land on ‘Sumner’ trees are from ‘Desirable’ trees and are not suited to infecting ‘Sumner’ leaves. However, the few that are pathogenic to ‘Sumner’ will reproduce and, over time, scab may become more of a problem. The greater the number of ‘Sumner’ trees that are planted, the more quickly this may occur. This leads to the cycle we commonly see, where new cultivars start out seeming highly resistant, but over time appear more and more susceptible.

‘Desirable’ is an example of a variety that once had good levels of resistance but which now is very susceptible. The variety itself is not changing, rather the pathogen is adapting to the variety. On the other hand, a few varieties like ‘Elliot’ have had excellent levels of resistance for many years. Currently it is not easy to predict how a variety’s resistance will hold up over time.

Alternate Bearing

Alternate bearing is another serious problem facing pecan production. This refers to a tendency for the pecan tree to produce many nuts of poor quality in one crop year, followed by a year in which the tree bears a very light crop. Alternate bearing appears to be controlled by two mechanisms. Growth regulators produced by the developing nuts suppress the induction of flower buds for the next season’s bloom. Secondly, excessive crop loads can leave trees depleted of stored carbohydrates, so flower buds are aborted the following spring.

Alternate bearing significantly affects pecan marketing and the price obtained by the grower for his crop. While all pecan trees have a tendency to bear alternately, some varieties are much better at producing regular crops than are others. Probably more pecan varieties have been eliminated from Georgia orchards because of their tendency to alternate bear than for any other reason except scab susceptibility.

Give a lot of thought, therefore, to the alternate bearing tendency of a particular variety before planting. The alternate bearing index (I) is a measure of a cultivar’s tendency to produce alternating high and low yields. This can be a valuable tool when making comparisons of varieties. The range is from 0 to 1, with 0 = no alternation and 1 = complete alternation, which would be no yield every other year. The producer can temper the alternate bearing of some varieties with proper management of the crop load and fertility. A detailed discussion of these management practices can be found in the University of Georgia Cooperative Extension Bulletin 1304, Cultural Management of Commercial Pecans.

Precocity

Precocity is the ability of a particular variety to begin bearing nuts at an early age. This trait is best determined by comparing the average yield among varieties from years 1-10. A precocious variety like ‘Cape Fear’ can be of benefit in that the producer can begin

to harvest a marketable yield at an earlier point in the life of the orchard than he can with other less precocious varieties. Unfortunately, precocity is often associated with excessive fruiting or overloading, resulting in poor quality as the tree becomes mature. Again, growers should not let the overloading tendency alone determine their variety choices because there are management tools available that can help reduce the impact of this problem.

Nut Maturity and Harvest Date

Pecans are traditionally marketed and used during the Thanksgiving and Christmas holiday seasons. As a result, early harvest is required to supply nuts for the holiday market. Early maturing varieties usually bring higher prices than later maturing varieties, although this is not always the case. For example, ‘Sumner,’ a late-maturing variety, can often bring a better price than that obtained from poor quality early maturing varieties.

Another benefit of early nut maturity is that nuts can be harvested under favorable conditions of dry weather in the southeastern United States. Cloudy, wet and cool weather can delay harvest and lead to a deterioration of nut quality. Growers should only plant very early maturing varieties like ‘Pawnee’ if they are able to harvest them promptly, otherwise bird and squirrel depredation can be severe.

Pollination Type

Pecan trees bear male and female flowers separately on the same tree. Pecans generally fall into two categories with regard to pollination. Type I varieties are termed protandrous. In type I varieties, the pollen matures before the pistil is receptive. Type II varieties, in which the pistil becomes receptive before the pollen matures, are termed protogynous.

Viable pollen must be available for the female flowers during the receptive period in order for a tree to set a crop. Self pollination seldom produces large crops and leads to poor nut growth and development, resulting in poor nut quality. Therefore, it is recommended that a combination of compatible varieties be planted to ensure pollen release throughout the pollination period. This can best be accomplished by planting at least two “pollinator varieties” in the orchard. A pollination chart is listed in Table 1.

Environmental conditions can have a significant effect on bud break and therefore pollen shed. Delayed pollen dispersal occurs under cool, wet spring conditions, and accelerated catkin development occurs during warm spring weather. This makes the inclusion of more than one pollinator in the orchard vitally important to ensure effective pollen shed at a time when female flowers are receptive.

Research indicates that effective pollination may decrease at distances greater than 150 feet from a pollen source. A rule of thumb is that pollinators should be no more than three rows apart. Pollinators can be blocked in rows, or pollinator varieties with similar nut and kernel characteristics to main varieties can be positioned within main variety rows. An effective alternative to blocking varieties is to place a pollinator at every fifth tree within every fifth row. This will provide adequate pollination, and the amount of pollinator nuts will be small enough the crop will not bring lower “blended” prices.

Nut Size and Quality

Nut size is a dominant factor in the selection of a variety and can be important for several reasons. Consumers tend to prefer large pecans; they can be marketed in or out of the shell; a large nut is more economical to shell; and most importantly, large pecan halves generally sell at a higher price than smaller halves.

The disadvantage of a large nut is that it is more difficult to fill and consistently obtain good quality kernels. Nut size is normally measured as the number of nuts per pound. In general, the larger the nut, the fewer nuts per pound. Each variety has a characteristic nut count, with a count of 40 to 50 nuts per pound being ideal.

Nut quality is determined primarily by the percent kernel. Percent kernel is the proportion of the nut that is kernel or meat. Percent kernel varies with soil moisture and crop load; however, each variety has a characteristic kernel percentage. Typically, most cultivars show a drop in percent kernel as the trees age. This is because young trees are producing relatively light crops and have more than enough leaves to support the developing kernels. As the trees mature, however, they set heavier crops and become limited in their ability to fill all the nuts.

Tables 2 and 3 list the recommended commercial pecan varieties for Georgia along with various characteristics of each that may aid in the grower’s decision making process. Varieties recommended for trial are included in Table 4. Figures 1-17 throughout the publication indicate nut size and kernel color for each of the recommended varieties. When choosing a variety, bear in mind that there is no one best variety. All selections have both weak and strong points. The key is to find a variety that will best suit the orchard situation.