Alternate bearing intensity of pecan cultivars

The Coastal Plain Experiment Station has been evaluating pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars for over 75 years. Using annual yield data from this program, the alternate bearing intensities (I) of 66 pecan cultivars and numbered U.S. Dept. of Agriculture (USDA) selections were determined. Values ranged from 0.19 to 0.93 in young trees, and from 0.27 to 0.91 in mature trees under high-input production practices. The adoption of fungicides, insecticides, and irrigation during the last 30 years has reduced the average I value from 0.70 to 0.55. I was negatively correlated with both nut yield and nut weight. All but one cultivar recommended for commercial production in Georgia have I values lower than the average of 0.57 for all cultivars in this test. Values calculated early in a tree's productive life cycle were highly correlated with those of mature trees.