Flower bud abscission in apricot: Competition between vegetative and flower buds, and effects of early defoliation and high pre-blossom temperatures

SummaryFlower bud abscission is an important factor in apricot (Prunus armeniaca L.) yield reduction reaching 80% or more in several cultivars like ‘Guillermo’. In this work we studied competition between vegetative and flower buds, and the effect of early defoliation (relative to canopy development), and the high pre-blossom temperatures (increasing by bagging the maximum sunny day temperatures by 6–7°C), on flower bud abscission in apricot ‘Guillermo’. Flower bud abscission appear to be due mainly to the internal balance and competition between vegetative and flower buds. Results showed an influence of the removal of vegetative buds on the reduction of the number of flower buds abscised. High pre-blossom temperatures in winter, during the period of rapid floral development, appear to be the other important factor increasing flower bud abscission. Finally, damage to the canopy in autumn, or early defoliation, had no important influence on flower bud abscission, although a higher percentage of buds abscinded was observed in defoliated branches.