Performance of Three Scab-resistant Pecan Cultivars in Southern Georgia in the Absence of Fungicide Application

Abstract

Current economic conditions demonstrate the need for disease-resistant, highly productive pecan (Carya illinoinensis) cultivars for the southeastern United States that can generate high yield potential and can be produced at a reduced cost to enhance grower profit margins. The objectives of this study were to evaluate the performance of the pecan cultivars Lakota, McMillan, and Excel in the humid growing region of the Coastal Plain of Georgia, USA, in the absence of fungicides. In addition, recognizing the excessive nut production of ‘Lakota’, we evaluated the response of ‘Lakota’ to mechanical fruit thinning. Four trees each of ‘Lakota’, ‘McMillan’, and ‘Excel’ were selected randomly for sampling. Trees within this orchard block receive no fungicide applications. Pecan scab (Venturia effusa) was not observed on any cultivar evaluated throughout the study. Powdery mildew (Microsphaera alni) was observed on all cultivars, but was significantly greater on ‘McMillan’ in 2020 and 2022 as a result of drier conditions in those years. Based on current data, all three pecan cultivars evaluated during this study are suitable for commercial production; however, ‘Lakota’ and ‘Excel’ performed best under these conditions in terms of nut yield. There was no consistent difference in nut weight among cultivars. ‘Lakota’ has the greatest potential in terms of percent kernel, averaging 58% kernel compared with 49% and 52%, respectively, for ‘Excel’ and ‘McMillan’. However, in years of excessive cropping, percent kernel of ‘Lakota’ is reduced significantly. Mechanical fruit thinning increased the following year’s production of ‘Lakota’ by 82% over nonthinned trees.