Effect of Fruit Thinning on Size and Quality of ‘Stanley’ Plum (Prunus domestica L.)1

Hand thinning during late June drop increased fruit size and improved quality of ‘Stanley’ plum as indexed by soluble solids and color development. Crop load within the range of 200 to 990 g of mature fruit per cm 2 trunk cross-sectional area was negatively correlated with fruit size, soluble solids and color. The percentage of mature fruits with cheek diameter less than 35 mm increased as crop load increased. Total flower buds and flowers per spur, and flowers per flower bud, were not significantly affected by fruit load in the range of 0.5 to 2.0 fruits per spur the previous season. However, a weak negative relationship was found between fruits per spur and flower buds produced per spur with a wider range (0 to 8 fruits/spur) in fruit load.