Drought Damages Pecan

Georgia’s pecan harvest has the advantage of being geographically earlier than Texas, New Mexico, and Arizona. Cultivars with early nut maturity and high kernel quality would further enhance Georgia’s market advantage. Pecan crosses were made at The University of Georgia Horticulture Farm at Watkinsville, GA from 1989 to 1995. The objective was to develop cultivars with early nut maturity, nut size less than 55 nuts per pound, kernel percentage higher than 55, and commercially acceptable scab resistance.
Pawnee was selected as the parent for incorporating early nut maturity which is about 3 weeks before Stuart (Sparks, 1992). The nut is large (49 nuts/lb.) with a moderately high percentage kernel (57%).

Pawnee is an excellent cultivar under arid and semiarid conditions, but it has three major deficiencies when grown in Georgia. One, under conditions of stress, primarily fruiting stress, the kernel’s seed coat develops conspicuous and unattractive dark spots which convey a dirty and unacceptable appearance to the consumer. When speckling does not occur, kernel appearance is very acceptable and the nut sells at a premium. Two, Pawnee is highly susceptible to scab (Nesbitt et al., 2005). Three, during a heavy “on” production year, kernel development is poor resulting in a high percentage of unacceptable nuts or nuts that must be sold at a reduced price.

Desirable was selected to cross with Pawnee because, traditionally, it is the best pecan cultivar for southeastern U. S. Desirable rarely over fruits; as a consequence, alternate bearing is minimal and, in most years, a commercial crop is produced. Minimum alternate bearing occurs because the fruit is thinned from year to year during the second fruit drop (Sparks and Madden, 1985). Because of this inherent thinning mechanism, the kernel (52%) of the characteristic large nut (47 nuts/lb.) is well developed or “filled out” (Sparks, 1992). Within the past several years, presumably, a new race of the fungus causing scab on Desirable has evolved making the disease extremely difficult to control during wet growing seasons.

The original Byrd seedling was from a cross made in 1989. The seedling first fruited in 1997. In 2001, the seedling was selected for trial and, in 2002, an experimental planting was established at NILO Plantation, Albany, GA. In 2003, fruiting trees of Desirable were top worked to Byrd at three Georgia locations (NILO Plantation, Albany; Graham Angus Pecan, Leary; and Pine Knoll Pecan, Cordele) to evaluate alternate bearing tendency and nut quality attributes which can be modulated by heavy fruiting stress inherent to mature trees. Top working onto older trees simulates a mature tree and thus reduces the time required for evaluation.

Budbreak in Byrd is about 3 days before Stuart. The leaves of Byrd are dark green as in the Pawnee parent. Leaflet orientation is also similar to Pawnee, that is, the opposite leaflets are often oriented at 180o relative to each other whereas leaflets of most pecan genotypes, including Desirable, droop to varying degrees. The tree is a vigorous grower, more so than Desirable. The vigorous growth increases the potential fruiting surface early in the life of the tree. Tree form is moderately upright as in Pawnee and not spreading as in Desirable. Date of nut maturity is similar to Pawnee or 18 to 21 days before Stuart.

Byrd produced 2.5 lbs. of nuts/tree compared with six nuts per tree for Desirable the 4th year from planting. During the 5th year, production per tree was 8 pounds versus about 1 pound for Desirable. Nut size was 46/lb. for Byrd and 46/lb. for Desirable. Soil moisture was excellent and under lesser soil moisture, nut size for both cultivars are correspondingly less. Percentage kernel was 62.1% for Byrd and 52.1% for Desirable, again with excellent soil moisture. Byrd’s shell is thinner and kernel percentage is higher than Pawnee. The thin shell and higher kernel percentage of Byrd increase the probability of fruit split (“water split”) when the fruit is in the maximum liquid endosperm stage (“water stage”). Water split occurs only if the maximum liquid endosperm stage coincides with a wet soil and rain-induced high humidity. Observations confirm that Byrd is more susceptible to water split than Pawnee but, so far, fruit split has been minor. Nevertheless, fruit split is a potential problem.

The nut shells exceptionally well in that the percentage of kernels with intact halves is very high with chipped or broken kernels being less than 5%. Tiny bits of packing tissue (inner shell tissue) sometimes sticks in the ventral (belly side) groove of the kernel, but, in most cases, they are easily dislodged. However, this has not been a concern to growers, buyers, or processors. The kernel is plump with deep but wide dorsal (back side) grooves, glossy, and attractive. Color is similar to Desirable. In striking contrast to Pawnee, speckling of the kernel has not been a problem with Byrd. The nut, its cracking ability, and its kernel quality were evaluated by a nut broker, a buyer, and four processors. All rated the nut and kernel very high and without apparent deficiencies.

Precocity of Byrd is very high and much greater than Desirable as indicated earlier. Byrd’s precocity was also evident following top working of older Desirable trees to Byrd in 2003. The trees fruited heavily the second year after top working. Precocity and prolificacy are highly correlated; thus, if a cultivar is precocious as a young tree, it will be prolific as mature tree (Sparks, 1990). Because of Byrd’s precocity, large nut, and large cluster (2.9 for Byrd and 1.7 for Desirable) it would be expected to bear alternately with increasing tree maturity as occurs with most cultivars, including its Pawnee parent. The original Byrd tree began to bear alternately in 2004 or the 8th year of fruiting although a commercial crop was produced during that year and subsequent “off” years. Trees top worked to Byrd in 2003 began to bear alternately the second year following fruiting but, like the original tree, have produced a lower but commercial yields during the “off” year.

Variability in percentage kernel in a cultivar increases with prolificness (Sparks, 1990), that is, the percentage kernel or degree of kernel development is less during the “on” than during the “off” year. To date, kernel percentage of Byrd has not differed statistically during the “on” vs. “off” fruiting cycle although it was numerically lower during the “on” years (62.7%) than the “off’ years (63.4%). So far, this contrasts with Pawnee and most other cultivars with similar nut size. However, as the tree matures and the proportion of wood to leaves increases, lower quality during the “on” year and alternate bearing may be accentuated. In contrast to Pawnee and many other cultivars, shuck decline (Sparks et al., 1995) as has not been a problem during the “on” year.

Byrd’s precocity and prolificness indicate that its long-term production per acre will not be limited by lack of yield potential as such, as is the case with most pecan cultivars. Instead, Byrd’s production will be determined by how well the grower controls excessive fruit production using mechanical fruit thinning (Smith et al., 1993). Thus, as with almost all pecan cultivars, Byrd should not be planted unless fruit load is controlled by mechanical fruit thinning. The ability to mechanically fruit thin Byrd was evaluated. The fruit were thinned with ease in contrast to Kiowa which is difficult to thin.

Byrd is a protandrous cultivar, meaning it sheds its pollen before pistil receptivity. At Athens, GA, Elliott, Schley, and Stuart are effective pollinizers for Byrd. Byrd, in turn, is an effective pollinizer for Elliott and Schley but not for Stuart. Pawnee and Desirable are not effective pollinizers for Byrd.

Although not immune, Byrd has a high resistance to scab. In an unsprayed trial, Byrd fruit had a scab rating of 1.6 whereas the rating for Desirable was 5.0 (1 = no scab, 5 = nut is not salable). These data are especially significant in that they are from the 2005 season which was unusually wet, thus, conditions were ideal for scab development. Consequently, the threat of major crop loss in Byrd from scab is low at the present but there is no assurance that Byrd will remain highly resistance to scab in the future.

The leaf has good resistance to black pecan aphid and is better than Desirable. Because the fruit of Byrd mature early, application of insecticides for hickory shuckworm control will have to be applied earlier than for conventional cultivars such as Stuart. The same is true for its parent, Pawnee.

Byrd was released due to its precocity, early nut maturity; kernel quality highly suited for a range of uses; ability of mature but small trees to produce well-developed kernels under high fruiting stress; high resistance to scab, black pecan aphid, and shuck decline. Byrd is recommended for trial only.

Availability

Byrd trees are propagated and marketed by Patten Seed Company, P. O. Box 217, Lakeland, GA 31635-2382. The company holds an exclusive licensing agreement with the University of Georgia. Consequently, graft and bud wood are not available for distribution. A U.S. Plant Patent is pending.

Trees will not be available in 2009 and availability will be limited in 2010. Afterwards, availability should increase significantly.

Byrd Pecan - A New Cultivar Producing Early Maturing, High Quality Nuts

Byrd Pecan - A New Cultivar Producing
Early Maturing, High Quality Nuts