Mechanical Fruit Thinning Enhances Production of Cape Fear and Sumner Pecan

The effects of mechanical fruit thinning on pecan [Carya illinoinensis (Wangenh.) K. Koch]  yield, nut quality, and profitability was assessed for the cultivars ‘Sumner’ and ‘Cape Fear’ . Ten 20-year old trees of both pecan cultivars growing in a commercial pecan orchard in Irwin County, Georgia were used for the study.  Trees were selected based on uniformity of size, vigor, and excessive crop load.  Trees were spaced 12.2m X 12.2m and were drip irrigated.  Trees were in good health and were managed according to University of Georgia Extension recommendations.  Treatments were replicated five times in a randomized-complete block design.  Five trees of each cultivar were mechanically thinned for 8 seconds by trunk shaking to remove approximately 30-40% of the fruit on each tree on August 1, 2007, and five trees were non-thinned. Initial crop load for all trees was excessive in 2007 with ³85% of terminals bearing fruit on each tree at the time of thinning.  The OFF year return crop and return crop value of both ‘Cape Fear’ and ‘Sumner’ was increased by mechanical thinning in the ON year.  This enhanced the 2-year average value of both cultivars.  Increased profitability of these cultivars with mechanical fruit thinning results primarily from higher yields and prices in the OFF year of production, which offset any loss in yield and/or crop value generated by fruit thinning in the ON year.  Premature germination of ‘Cape Fear’ pecans were reduced by 29% with mechanical fruit thinning.